− Male-male competition...2
− Female choice...2
− Sexual conflict...3
Secondary sexual trait and mating system. ...3
Intensity of sexual selection...5
Goal and scope...6
− Intensity of sexual selection in deer...8
− Data analysing...8
By performing a comparative analysis and using phylogenetic relationships of the Cervidae
family this study aimed to address whether or not sexual selection may play a role in the extinction
of species by making species more vulnerable to extinction. The role of sexual selection in making
species more vulnerable to extinction is largely unexplored, and several factors such as ecological
and life history traits may increase the risk of extinction.
In all species of the family Cervidae (Gilbert et al. 2006, Geist 1998,Groves and Grubb
2011,Meijaardand Groves2004,Price et al. 2005, Goss 1983) sexually selected characters plays a
main role in determining species status and thus potentially their probability of extinction. In this
study the intensity of sexual selection (measured as sexual size dimorphism, antler size and mating
system) and the rate of extinction (IUCN classification and anthropogenic effect) were counted as
factors to determine the role of sexual selection intensity in both species-rich and species-poor
By using the programme MESQUITE and phylogenetic trees, the results show an association
between species with larger body size and dimorphism, living in open habitats and having larger
antler size expanded to more than three tines; such species are mostly non-territorial and form
harems during the rutting season. The small species are territorial, live in closed habitats, are
monomorphic and have small antler size limited to two tines or less. Moreover species that are
more subjected to habitat degradation and anthropogenic effects tend to become smaller in size.
Extinction risk for the species-rich clades with small sized, territorial and small antler sized
species is lower than for those consisting of species with larger antler size, larger body size, living
in open habitats and using harems as mating system.
To sum up, the intensity of sexual selection in larger species in deer family put them in risk of
extinction; but on the other site, small species are more adapted to the environment by choosing
different strategy in mating system, and reducing antler and body size thus diminishing the
Darwin in the “Origin of species” (Darwin 1859) indicated that there is struggle for existence among species that leads to variation. He stressed the term “selection” as a principle for extinction or adaptation (Darwin 1872). In the “Descent of man”, Darwin (1871) mentioned two types of selection, natural selection and sexual selection; he defined natural selection as struggle for existence among individuals and sexual selection as advantages in reproduction which some individuals have over others in the same sex within species (Darwin 1871). Based on natural selection, alleles are selected which raise the competitive allocation of appropriate resources in to reproduction with investment in maintenance, repair and survival (Flatt 2011). At the beginning, sexual selection was a part of natural selection but later on, Darwin developed his theory that sexual selection can work against natural selection and that it can be non-adaptive for survival. On the other hand, Fisher (1930) gave Wallace opinion in which that sexual selection existed and Wallace tried to stress on natural selection as a principle of evolutionary description for biological phenomenon. These debates followed until middle of nineteenth century, the time that Ronald Fisher developed the concept of sexual selection as a Darwinian biologist (Fisher 1930). The modern approach talks about sexual selection as a special aspect of the natural selection theory with difficulties arising from unavoidable interactions between these two selections (Gayon 2010). The term of sexual selection and its mechanism is discussed and modified by many researches. The role of sexual selection in generating species biodiversity is a relatively well researched field and the emerging picture seems to be there is consensus that sexual selection may lead to divergence among populations and thus to speciation (Panhuis et al. 2001, Seehausen et al. 2008). Darwin’s explanation of the concept of sexual selection in “The Descent of Man and Selection in Relation to Sex” is followed by many researches that sexual selection could lead to sexual isolation and consequently speciation (Ritchie 2007).
Sexual selection is known as a struggle to reproduce between individuals of the same sex, generally male- male competition, which necessarily do not lead to death but less offspring; and female choice by which females prefer the most attractive individuals to mate with (Darwin 1871, 1872). Sexual selection is an important driver for morphological trait evolution in both male secondary sexual traits and female life history characters. Sexual selection is not limited by access to copulations as Parker (1994) mentioned, it can continue after mating (e.g. sperm competition after mating with different males). Female fitness increases through mating by multiple mating with
one male or mating with several males; female gets benefits from direct and indirect selection (i.e. direct phenotypic benefits and indirect genetic) (Andersson and Simmons 2006, Kolm et al. 2006).
− Male-male competition
Male-male competition and female choice both happen during pre and post copulatory competition. Pre-mating competition between males consists of combat or non-aggressive display and post-mating competition includes sperm competition and/or infanticide. Secondary sexual characters are used in male competitions in the most competitive sex. Traits that influence mating decisions can be phenotypic such as morphological, acoustic, olfactory, tactile or behavioural traits; they can be resources defended or produced by a signaller for example a nest or a territory (Candolin 2003). Male-male competition is important for females by facilitating female choice by increasing differences among males, it decreases risk of predation, spending energy and saving time and it prevents loosing mate opportunities; overall it speeds up intensity of sexual selection. Any alteration in signalling and trait expression might affect female choice. Therefore, if the signalling trait is costly for males during competition, then the cost declines by male condition; otherwise there is no adaptive female choice in response to that trait (Candolin 1999). Sometimes males try to overcome female resistance by evolving traits which is followed by evolving resistance in female as well; thus males tend to evolve new display traits that make them more adorned by new multiple ornaments. Preferences for new traits may cause indirect benefits due to increasing offspring’s reproductive success. These new traits might not be useful anymore to overcome female resistance and cause species extinction because those traits decrease fitness or are costly (Candolin 2003). Generally male signalling traits are under influence of inter and intra-sexual selection which they perform as quality indicators in mating choice and condition factors in male-male competition (Delaney et al. 2007, Faivre et al. 2003).
− Female choice
Cryptic female choice and differential allocation is categorized as post copulatory female choice. Godin and Briggs showed that mate preference in female guppy decrease by predation risk; this decrease associated with cost of viability of females. This response may affect the intensity of sexual selection and thus further evolution of sexually selected traits and female choice (Godin and Briggs 1996). Many researches have shown secondary sexually characters to evolve by female choice (Witte et al. 2000), also males can affect female traits by distinguishing between females ready to mate and therefore drive the trait in females. Witte et al. (2000) found that preferences to
adorned females or males increase by juveniles whom grow up with adorned parents by sexual imprinting; this result shows that the preferences for ornaments might change species without ornaments to species with conspicuous traits. The last result was in accordance with the conclusion from experiments on flycatchers that females learn to mate with artificially novel adorned males. If preference of exaggerated imprinted traits spread in populations then the proportion of females interested in novel ornamented individuals increase due to mating activities; the preferences of novel traits could drives pre-zygotic isolation before it happens genetically, thus rapid divergence is possible by sexual selection within species (Qvarnström et al. 2003).
− Sexual conflict
Many studies have shown that sexual selection gives benefits to females but on the other side, it can also be costly due to sexual conflict. Sexual conflict could be defined as a negative relationship between average fitness of males and females involved in mating activities that speeds up during reproduction (Pizzari and Snook 2004). Studies have stressed the effect of sexual conflict in co-evolution of male manipulation and female resistance, risk of extinction, influencing speciation and evolution of senescence. Hall et al. (2008) declared that any changes in environment that influence sexual conflict will have consequences for sexually selected traits in male and maintenance of genetic variation of those trait. They concluded that by manipulating the ability of both sexes to influence spermatophore attachment (sexual conflict due to attachment time of an external spermatophore), the intensity of sexual selection on male courtship call and body size is influenced by sexual conflict. Males may harm females directly (e.g. toxicity of the seminal fluid) or by reducing female survival during persistent courtship (Holland and Rice 1999). Because of negative consequences for females, conflicts between sexes may raise the resistance of females to signal traits, and also sometimes lead to sexually antagonistic co-evolution (Andersson and Simmons 2006).Moreover, in allopatric populations sexual conflict could accelerate the evolution of diversifying reproductive traits and consequently lead to reproductive isolation (Svensson and Gosden 2007).
Secondary sexual traits and mating system
As Darwin declared, differences in colour, ornaments or structures between males and females of any species that live in the same environment, is driven by sexual selection (Darwin 1872). He stressed that sexual selection drive the evolution of secondary sexual characters that cannot be explained by natural selection (Gayon 2011). The interactions between natural and sexual selection
determine evolutionary dynamics and changes in secondary sexual traits. Mathematical models and comparative studies have shown that secondary sexual traits might cause rapid evolutionary changes (Svensson and Gosden 2007). Sexually selected traits vary in expression and these differences are driven by sexual selection since they determine the reproductive success. Sexually selected traits vary among individuals, both in response to life history trade-offs and in short timescale as a response to environmental conditions (Griffith et al. 1999). Decrease in sexually selected traits due to predation is one example of response to life history trade-off.
Variation in secondary sexual traits correlates with intensity of male-male competition that finally determines reproductive success. Because of intra-sexual competition, male size dimorphism and weaponry evolve in response to sexual selection. For example, in species with high sexual size dimorphism, it has been shown that males in polygynous ungulates are more successful in reproduction with higher body size/mass and bigger horn or antler size/mass. Low sexual size dimorphism is associated with low levels of sexual selection but males may be more active than females in behaviour; these behavioural characters affect reproductive success more than morphological ones in such species. On the other hand, according to the agility-hypothesis small body size can determine sexual selection on small size in reproductive success. Vanpé et al. (2010) also concluded that in species with low sexual dimorphism, if females are selected for higher body size or mass, then the male body size is selected for smaller size. Dunn et al. (2001) also indicated that many factors influence the evolution of sexual dimorphism such as mating system and sperm competition. Mating system for each species is different and includes one of six categories, which are monogamy, polyandry, mostly monogamy but occasional polygyny, mostly polygyny, cooperative breeding and promiscuous mating systems. Dunn et al. (2001) declared that all the four types of dimorphism which they used in their research (testis size, plumage dimorphism, wing and tail length), are associated with mating system and sperm competition, except for body mass which had no relation to sperm competition.
According to the traditional explanation, variation in sexual dimorphism is driven by variation in mating system and type of parental care in species. Owens and Hartley (1998) showed that not all type of variation in sexual dimorphism is related to mating system, such as plumage-colour dimorphism that was associated with female choice and frequency of extra-pair paternity. In another study, Møller and Briskie (1995) indicated that testes size is correlated to sperm competition and extra-pair paternity. Sexual selection not only influences secondary sexual traits in males but also affects female life history traits; as Kolm et al. (2006) showed, sexual selection is a driver of high level of sexual size dimorphism and influences larger body mass and egg size in female Galliforms.
Intensity of sexual selection
Sexual selection intensity, as explained by Wade an Arnold (1980), is a function of variance in fitness in the two sexes, which itself depends on mating system and reproductive success. They mentioned this because sexual selection is regarded as an intra-sexual phenomenon (excluding sexual conflict), therefore male reproductive success could be a strong factor when measuring the intensity of sexual selection. According to what has been discussed above any differences on male attributes, female choice, sex ratio, sperm competition etcetera can affect the intensity of sexual selection in pre and post mating sexual selection (Wade and Arnold 1980). For example, male investment in resources affects the intensity of sexual selection by the fact that when food is scarce females tend to have larger size in order to compete with other females on nurturant males (due to the fact that male resource investment affects the number of copulations also affects female fitness by accessing the amount of resources to produce eggs). From the other side, sexual selection on females arises through male mating preference when nutrients limit the male mating frequency. Moreover, the intensity of sexual selection differs between females and males (Castillo and Núñez-Farfán 2008). In another example, Bro-Jørgensen used breeding group size with mating system to measure the intensity of sexual selection and he suggested that horn size and sexual body size increase with the size of breeding group and decrease with territoriality. These variations in secondary sexual traits could be explained by intensity of sexual selection within mating system (Bro-Jørgensen 2007).
On one side, Darwin stated, traits can evolve despite not being favoured by natural selection, and it leads to populations in an unstable state (Darwin 1871). On the other side, some theories predict that by the action of sexual selection, the rate of adaptation will increase in relation to environmental changes (Morrow and Fericke 2004). There are many ways by which environmental changes might result in evolution of male sexual signals and female choice. Changes in signals might cause sexual selection by changing female preferences or by changes in signalling environment. Also, the cost of having a signal might change by alteration in natural selection such as predation risk or parasitism. Moreover, changes in traits will cause changes in mate preferences by changes in the value of the altered signals or by changes in the cost of expressing a given preference (Easty et al. 2011). Thus, it is unknown whether there is a net gain or loss of species due to sexual selection. Modern comparative methods using phylogenetic relationships can be applied to identify evolutionary patterns and processes. Subsequently this leads to better understanding of the origin of character states and if they have evolved independently, and which factors could be responsible for extinction or speciation (Harvey and Pagel 1991).
unexplored. There are several factors which may predict a risk of extinction, consisting of ecological and life history traits of species. By affecting the rate of mortality and natality, sexual selection can increase the risk of extinction; for example in a population under intense sexual selection that may face increasing rates of predation, parasitism, raised sensitivity to environment and demographic stochactisity, including the possibility of Allee effects (Doherty et al. 2003, Kokko and Brooks 2003). Theory have shown that in a changing environment, a number of new selection pressures arise in the population due to the cost of sexual selection, and this might lead to extinction by intense female choice. For example, in a population that faces environmental degradation, the cost of signalling causes only a few males to survive until the breeding season and consequently may lead the population to extinction; the process of extinction continues until the signalling disappears due to decreasing the cost of trait (Tanaka 1996, Doherty et al. 2003). Overall the cost of sexual selection deals with ecological and genetic factors; ecological factors could be explained by “reduced effective population size because of reproductive skew, antagonistic co-evolution between sexes, tradeoffs between the size of sexual traits, and the size of other morphological character” (Doherty et al. 2003).
In this project I want to address whether sexual selection may play a role in the extinction of species by making species more vulnerable to extinction. I am doing this by performing a comparative analysis of the extant species of deer (Cervidae).
Goal and scope
Estimating the trade-off between life history traits and viability is the major principle to understanding the causes of extinction. For example, it has been proposed that the Irish elk became extinct because it evolved very large antlers (up to 40 Kg weight) (UCMP 2013). Males with larger antler was probably preferred by females but the excessive size of antler made it difficult for Irish elk to feed and consequently led to its extinction (Kokko and Brooks 2003).
My research is based on the following hypotheses: sexual selection not only leads to elevated levels of speciation but also to more extinction; also it is predicted that species subjected to intense sexual selection are also more extinction prone.
To measure the relation between sexual selection and extinction within the deer family I ask several questions. Does intensity of sexual selection lead species to be more vulnerable to environmental changes? How and in which way may the risk of extinction affect species to adapt to their environment? Are the changes in behaviour and secondary sexual traits similar in all clades in the Cervidae family? And do anthropogenic effects push deer species to choose different
7 reproductive strategies?
In this project a combination of extinction threat with estimates of sexual selection was used to test the hypotheses stated above. Referring to Issac et al. (2007), a phylogenic tree was applied to represent evolutionary history of species, mode of divergence and phylogenetic diversity. In a large phylogeny with many species (such as the tree of life), rate of extinction can be measured by the form of clades (e.g. monotypic, old or species-poor clades). However, there are some limitations to apply phylogenetic diversity: the length of branches is not available for dated species thus phylogenetic diversity mostly focuses on pattern of branches; also when using phylogenetic diversity, the focus is not on species. Using evolutionary distinctiveness combined with extinction risk has been used to identify endangered species with distinct evolution (Isaac et al. 2007). Using published records I aimed at deriving proxys for extinction risk for species by using IUCN data (IUCN 2006) following previously described approaches (Isaac et al. 2007). Thus extinction risk was scored as one or several categories according to IUCN-The World Conservation Union Red List- categorization system, such as: critically endangered, endangered, and vulnerable taxa. This system was used to identify threatened, non-threatened taxa. Other IUCN-listed categories such as extinct, extinct in the wild, lower risk, and data deficient were used (Spielman et al. 2004).
Exaggerated sexually selected structures (ornaments or weapons) may impose costs for animals during their different life stages such as by reducing viability, retarded growth of nearby organs (Nijhout and Emlen 1998, Emlen 2001). Hence there is a need to assess the level of intensity. Estimating the level of intensity of sexual selection was addressed using various proxys for intensity such as levels of social mating system, sexual dichromatism and sexual size dimorphism which have all been suggested to be measures of pre-mating sexual selection (Møller and Briskie 1995, Owens and Hartley 1998, Dunn et al. 2001, Kolm et al. 2006).
Species level analyses were conducted using supertrees of deer (Price et al. 2005). This is an excellent group for the proposed project since deer varies greatly in mating system (Greenwood 1980), sexual size dimorphism and sexual ornaments (antlers) and also varies in threat status.
The research is based on published literature and data collected from the internet and IUCN data. The list of species in the Cervidae family has been combined with the data of extinction risk by applying the different categories from the IUCN Red List. First, I identified the species within the family Cervidae with substantial variation in the traits (levels of social mating system, sexual dichromatism, secondary sexual characters and sexual size dimorphism) for assessing intensity of sexual selection (Appendix 1, Species descriptions). During the second stage, I collected a database with information on those traits. Assembling a phylogeny for the Cervidae was the next step which was followed by tree transformation and data (e.g. based on branch lengths, discrete traits, continuous traits), then I ran analyses under a phylogenetic comparative framework using the Mesquite program (Maddison and Maddison 2011).
For analysing the data, I used the supertrees methodology which assembles a consensus from smaller phylogenetic trees sharing some taxa in common (Sanderson 1998). The source of data for the phylogeny was gathered via articles consisting of phylogenetic data and web sites such as BIOSIS and BioScience. Bibliographies were used for additional data.
− Intensity of sexual selection in deer
Estimating the intensity of sexual selection in this study was based on social mating system, sexual ornaments (antlers) and sexual size dimorphism that have all been counted as a pre-mating measurement of sexual selection. The following types of sexual dimorphism have been used in other studies: body size, body composition, skeletal composition, brain and nervous system, other organs and metabolism, and weaponry (McPherson and Chenoweth 2012). In this study, body size, body height, antler size/shape and the level of mating system was chosen as measurements of sexual selection intensity.
− Data analyses
Data analyses were done with the software Mesquite (Maddison and Maddison 2011). In this program, I used sexual dimorphism, body size, body weight, antler size, IUCN classification, antler size as a secondary sexual trait, mating system and territoriality and mating behaviour as the main characters in a matrix. On the character states, the traits were traced on the phylogeny tree and in
this case I used the phylogeny of Gilbert and co-workers (Gilbert et al 2006). For the species that are not included in Gilbert et al. (2006), trees from Mejaard and Groves (2006), Pitra et al. (2004) and Price et al. (2008) were used to shape the final phylogenetic tree. From the tree I derived reconstruction coordinates of ancestral states by maximum likelihood. Currently each node is estimated independently (i.e., corresponding to PAUP's marginal reconstruction). The out-group consists of two species belonging to two different taxa of the suborder Ruminantia: Antilocapra
americana (Antilocapridae) and Moschus moschiferus (Moschidae).
Sexual dimorphism was based on the weights of females and males; those species with slight differences in weight between sexes were considered as monomorphic and those with large differences in weight (more than 1.5 times) were considered as dimorphic.
Body size was considered as shoulder height and species with less than 650 mm in shoulder height were included as “small” and more than 650 mm assigned as “large” species. For those species with lacking data in shoulder height, I used body length; species with a body length less that 1250 mm were considered as “small” and more than 1250 mm set as “large” species (Gilbert et al. 2006).
I used two IUCN classifications. First, eight categories were included: extinct, extinct in the wild, critically endangered, endangered, vulnerable, least concern, near threatened and data deficient. The second set of categories consisted of 1) Extinct, extinct in the wild, critically endangered, 2) endangered, vulnerable, near threatened and 3) least concern and data deficient. In addition, according to IUCN database, I considered anthropogenic effects such as hunting for trophy or meat, land use changes, habitat degradation, hunting by domestic animals etc. The severity of these effects was marked as severe, moderate and less impact in three categories.
Secondary sexual traits were scored as having antler or tusk in the males; in some species, tusk and antlers both exist and in some, there is lack of antler or tusk. Antler size was classified in five groups according to the following: 1) <15 cm; 2) 15- 50 cm; 3)50-100 cm; 4)>100 cm and 5) without antler (= 0).
As mating system, I put species in six categories based on the existence of: harems, leks, defending a spaced out territory, courting pairs, having a dominance hierarchy or a fission-fusion system. Moreover, the size of breeding group was taken into account as 1) small-medium group size and 2) medium-large group size. Being territorial was counted as one of the main factors and considered separately for each species.
The behaviour was divided into two groups, mating behaviour and daily behaviour. As mating behaviour I considered aggressive behaviour, non-aggressive behaviour, fighting and defending female/s. Daily behaviour habits included being solitary/sociable, crepuscular, nocturnal/diurnal, living in a small group or in pair, or in a family group.
Habitat type was classified in two groups based on IUCN data and were scored according to the following: open/disclosed (D) or closed (C) habitat. The first category consists of grasslands, marshlands, and open forests and closed habitat includes dense forests and marshes with reeds (Gilbert et al 2006).
The phylogenetic trees used were made based on complete mitochondrial cytochrome b gene sequences (Pitra
et al. 2004), mitochondrial
Cyt-b and CO2, and
four nuclear regions (Gilbert et al. 2006), elements of skull shape as determined by morphometrics (Meijaard and Groves 2006) and some other molecular studies (Wilson and Reeder 2005, Groves and Grubb 2011, Geist 1998). In this study, I used four different phylogenetic trees (see below).
The Cervidae family is traditionally taxonomically divided into two groups: the old world deer (Muntjacinae and Cervinae) and the new world deer (Odocoileinae and Hydropotinae).
Figure 1: The Cervidae family is divided to two main clades: Cervinae and Capreolinae. The Cervinae clade itself is divided into two main clades known as Cervini and Muntiacini. Also Capreolinae is divided into three main clades consisting of Capreolini, Odocoileini and Alcini. Two species, Moschus moschiferus and Antilocapra Americana have been assigned as out-groups. In the case of accessing different data on each species, the Gilbert paper (Gilbert et al. 2006) was used as a reference (■ the species which referred to Gilbert et al. 2006; ■ the species which gathered from other researches - Wilson and Reeder 2005, Groves and Grubb 2011, Geist 1998, Pitra et al. 2004,Meijaard and Groves 2006).
According to nuclear and mitochondrial markers, the Cervidae is also divided into two main clades: Cervinae and Capreolinae. The Cervinae clade itself is divided into two main clades known as Cervini and Muntiacini. Also Capreolinae is divided into three main clades consisting of Capreolini, Odocoileini and Alcini. Two species, Moschus moschiferus and Antilocapra americana have been assigned as out-groups. In the case of accessing different data on each species, Gilbert et al. (2006) was used as a reference, Figure 1.
To compare the trees, results was confirmed by other studies, in which all ancestors of species were more or less placed in the same positions and the different trees showed similar results (Mejaard and Groves 2006, Pitra et al. 2004, Price et al. 2008). Using pairwise comparisons by testing character correlations also confirmed the results by Gilbert et al (2006). In the ancestor of
Cervidae, the males were large (shoulder height >650mm), bigger than females, with three-tined to
four-tined antlers, without upper canines, and they lived in open habitats. However, the ancestors of Muntiacus + Elaphodus and Capreolus + Hydropotes, the analyses suggest a completely different pattern: they lived in closed habitats, and the males were small (shoulder height<650mm), similar in body mass to females, with two-tined antlers (Figure 2, 3).
Figure2: Correlation between body size (independent character) and antler size (dependent character). Positive (Green): cases in which one of the taxa has a 1 for both characters and the other taxon has a 0 for both. (00 vs 11); Negative (Red): cases in which one of the taxa has a 1 for one character and a 0 for the other and the other taxon has the opposite. (01 vs 10); Neutral (Grey): cases in which the taxa disagree in the independent character, but have the same dependent character. (01 vs 11) or (00 vs 10); Reminder (Blue): cases in which the independent character is the same for both taxa. Here, body size is considered as independent character and antler size as dependent character.
The results show that 49% of all species have large body and are dimorphic and 40% are small and monomorphic. It also indicated that 95% of smaller size species are monomorphic and 85% of the large species are dimorphic.
Antler size in the ancestors of Alceini and Odocoileini ranked as four (>100 cm), in Muntiacini 1 (>15 cm), in Capreolini 2 (15- 50 cm) and in Cervini 3 (50-100 cm). Also in Muntiacini and Hydropotes the tusks or upper canines are developed. In the ancestor of Odocoileini (Rangifer tarandus) both sexes carried antlers.
Based on the IUCN red list
classification, the ancestors of the species in the subfamily of Muntiacini, Alceini and Capreolini are categorised as data deficient or least concern
while species from Odocoileini are near threatened, vulnerable or endangered and the Cervini subfamily is classified in the extinct, extinct in the wild and critically endangered
Figure 3: Character correlations have tested by comparing reconstructions visually. Correlation between habitat openness (C=close; D= Open) and body size (S=Small; T= Tall). Likelihoods using a speciation/ extinction model reduced from the BiSSE model (Maddison, Midford and Otto 2007)
Figure 4: Correlation between Antler size and IUCN classification as an extinction risk. Both species with large and small antler size have shown extinction risk as located in second category of IUCN (Vulnerable, near threatened, endangered).
Figure 5: In the Cervidae family, all subfamilies are under moderate impacts of human life, but Cervinae endures severe effects of habitat degradation, wild life
mismanagement, pollution, chasing by domestic dogs and illegal hunting.
The correlation between antler size and extinction criteria shows (Figure 6) that the highest percentage of species with smaller antlers are placed in third IUCN category but both groups (large
and small antler size) show extinction risk by being locating in the second category of IUCN (vulnerable, near threatened, endangered). 50 percent of the species with smaller size of antlers are less concerned or data deficient while 38% of species with larger antlers are listed in first or second IUCN categorisation (Figure 4). Moreover the effect of human impact is moderate to severe on both large and small antler size species (Figure 5).
The correlation between body size and IUCN classification shows that both small and large sized deer are in the categories two and three and 5.2% of the large species are in first category of extinct/extinct in the wild. In addition there are moderate to severe anthropogenic effects on both small and large sized deer (52.5 % moderate, 31.5% severe impact) (Table 1).
As results show, in Cervidae family, all subfamilies are under moderate human impact, but
Figure 6: Character correlations have been tested by comparing reconstructions visually. Correlation between Extinction criteria (1: Extinct, extinct in the wild, critically endangered, 2: endangered, vulnerable, near threatened, 3: least concern, data deficient) and antler size (1: <15 cm; 2: 15- 50 cm; 3:50-100 cm; 4 :> 100 cm; 5: without antler = 0). Likelihoods using a speciation/extinction model reduced from the BiSSE model (Maddison, Midford & Otto 2007)
Body size IUCN Count Percentage
S 1 0 0 S 2 13 22.81 S 3 17 29.82 T 1 3 5.26 T 2 13 22.81 T 3 11 19.30
Body size Anthropogenic effect Count Percentage
S 1 9 15.79 S 2 17 29.82 S 3 4 7.02 T 1 9 15.79 T 2 13 22.81 T 3 5 8.77
Table1: The correlation between body size and IUCN classification. Both small and large size deer are in category two and three with 5.2% of extinct or extinct in the wild of large species. The results show moderate to severe anthropogenic effect on both small and large size deer.
Cervinae endures severe effects of habitat degradation, wild life mismanagement, pollution, chasing
by domestic dogs and illegal hunting.
The ancestors of Muntiacinae and Capreolinae were territorial while Cervini, Alceini and Odocoileini were not territorial and their mating system consisted of harems and protecting females. In total, 72% of the small species are territorial and 72 % of the large species are not; my analyses suggested that most monomorphic species are territorial and 80% of dimorphic species are non-territorial. Among these species, Muntiacini has aseasonal reproduction and the other groups reproduce seasonally.
My analyses also show that there is a significant correlation between mating system/ territoriality and anthropogenic effects. In addition the correlation between extinction rate (IUCN classification) and antler size/number of tines/ territoriality and habitat openness is significant. Species with larger body size, larger antlers and being territorial are more prone to extinction.
The group of large species mostly posed in first and second category of IUCN red list (1: Extinct, extinct in the wild, critically endangered, 2: endangered, vulnerable, near threatened) while the rest of species in this family were assigned to the category of least concern or data deficient.
Based on the IUCN data of species distribution, species mapping by GIS (ESRI Inc. 1999) shows different distributions among small and larger deer. Based on Giest (1998), smaller species live in low latitudes while those with larger body size are more common in higher latitudes. This follows Bergmann’s rule, species with smaller size live in warmer region and larger size in colder areas. This means that in low and high latitudes, body size decrease and in seasonal climate regardless of regular but temporary food access, the size of body increases and the peak is at 60 N◦ (Figure 7).
Figure 7: The distribution of small and large deer in the world based on IUCN map. Smaller species live in low latitude while those with larger body size are more common in higher latitude
Sexual dimorphism and secondary sexual characters not only reflect adaptation in those species with high reproduction success but also represent species with high risk of extinction. Increasing rate of predation, parasitism, raised sensitivity to environment and demographic stochactisity, including the possibility of generating Allee effects, changing environment due to increasing the number of selections and cost of sexual selection in population might lead to extinction.
Antler development has been a debatable subject among scientists for a long time and several theories to explain the adaptive significance of these ornament has been put forward. One theory proposed antlers develops as a weapon for mutual combat during rutting, which is used for pushing or wrestling rather than killing. This theory is supported by the fact that during the period after rutting is followed by shedding the velvet and casting off solid/ bony antlers (Goss 1983). Another theory discusses the displaying, which is also supported by the previous theory but not necessarily head-to-head combat (Goss 1983). Antler growth by accentuating the size of the head (especially in larger deer species) plays the same role as horn size, mane development, and swollen necks in other species. For example in Irish elk, the growth of antler out to the sides rather than upwards is evidence that antlers were developed to impress others visually. Moreover, a third theory argues that antlers are used for thermal radiation by releasing excess body heat (Goss 1983). This theory says that loosing velvet and casting antlers in the winter is preventing heat loss. However, this cannot explain the presence of antlers of tropical species should then be larger or being permanent, but they are not. The last theory is based on olfactory projection in which the antler has an abundance of sebaceous gland in the skin. Rubbing antlers to the tree or body is used when scent marking (Goss 1983). To sum up, antlers can be used as weapons in aggressive behaviour but may also have secondary functions (Goss 1983). Antlers have appeared in female rein deer and have also been reported to be common in female roe deer, white-tailed deer and mule deer, while less common in sika, red deer, wapiti, and moose (Goss 1983).
The other measurement of sexual selection intensity is sexual size dimorphism. Sexual dimorphism has evolved through sexual selection or adaptation for gender-specific niche divergence under the pressure of ecological or reproductive factors. Body size for those species with a polygynous mating system is greater and depends on the ratio of males to females in local area (Alces alces) (McPherson and Chenoweth 2012). Generally body size dimorphism is correlated to weaponry, (lack of) parental investment, access to resources and aggression (McPherson and Chenoweth 2012).
Mating system may also drive dimorphism among species having polygynous mating system. Species that have harems are more dimorphic than territorial ones; and this is suggested to be a result of the intensity of sexual selection (Weckerly 1998, Bro-Jørgensen 2007).
Geist (1998) showed that species at the beginning of colonisation of a new habitat had larger body size but after reaching their carrying capacity, populations tend to reach smaller size. This supports the result of this study in which derived species tended to be smaller especially in Mazama and Muntjacus species. These species face more habitat degradation and anthropogenic effects, thus they have become smaller. Moreover, the connection between body size and environment arises in the terms of a predator-limited and resource-limited fauna. In a predator-limited fauna, the body size increases, competitive ability reduces and food acquisition organ has not developed (e.g. teeth size decrease and are less complex in structure), while in resource-limited fauna body size decreases and it is followed by high level of competitive ability and improved food acquisition organ (for example teeth size increase and become more structural complex). In the second category the ornaments remains modest (Geist 1998). However, by an alternative view in some species of the deer family, the female body size increases in resource-limited areas in order to compete with other individuals (Castillo and Núñez-Farfán 2008) and the probability of sexual size dimorphism decrease as observed in some species in Muntjacus, the Mazama subfamily and the Pampas deer.
My results show that species with larger body size are more dimorphic. Larger species live in open habitats and have larger antler size, the number of tines is higher and they are mostly non-territorial and form harems during the rutting season. However, the small species (Muntjacus and Elaphodus) are territorial, monomorphic with small antler size and the number of tines limited to two. As noted by Randi et al. (1998), a dramatic size reduction of spiked antlers in the South American genera Pudu and Mazama, suggests that the reversal of morphological trends is possible as consequence of selection for small body size (Randi et al. 1998). In addition, according to Merino and Rossi (2008), the first deer that entered South America was a medium-sized species with branched antlers; these would have given rise to taxa with the appearances that it is more conservative, have smaller size and simple antlers as in Mazama and Pudu (Merino and Rossi 2008). This result also follows the conclusions by Gilbert et al (2006) in that Mazama species choose the closed habitats with dense vegetation, therefore their antler size, body size have become reduced and sexual size dimorphism tends to become absent. In addition, the antler size depends on the environment (open or closed) and the resource limitation; in resource-limited and closed habitats, antlers are smaller while the size of antlers increase with the degree of food availability and openness of the habitats (Giest 1998). Existence of tusks in smaller species (Muntjacus) is adding to their small antler, and these are known to be used as weapons to defend their territories and used in fights with other males. The regularity of antler shedding in muntjacs depends on
continually defending resource-rich territories (irregular shedding) or relates to seasonal defence and reproductive functions (regular shedding) (Giest 1998).
The pattern of the tree in Muntjacini clade shows deep split between Muntjacus and Elaphodus. The clade of Muntjacus also is rich in species therefore the risk of extinction of clade is less than other sister clade (Elaphodus). The same result comes up with the clade of Odocoileini;
Rangifer tarandus has higher risk of extinction than sister clades Mazama because of species-poor
clade. Moreover, in Capreolinae clade, Capreoloni and Alcini have higher risk of clade-extinction than Odocoileini clade (sister group).
Extinction risk for those clades with small species, territorial and small antler size is less than those clades consisting species with bigger antler size, larger body size and shaping harem as mating system.
To sum up, in all species of the Cervidae family, sexual selection seems to play a main role for the probability of extinction. Clearly, the intensity of sexual selection (sexual size dimorphism, antler size and mating system) and the rate of extinction (IUCN classification and anthropogenic effect) differ among species and clades. The extinction rate has been affected by human impact and anthropogenic effects. The overall estimate of the likelihood of extinction/speciation indicates 85.57587659 with lambda (speciation rate) 0.46228503 and mu (extinction rate) 1.943431099E-5 in the Cervidae family. In some subfamilies (Muntjacus and Mazama), the risk of extinction (such as habitat degradation and chasing by domestic dogs) causes the species to have evolved smaller body and antler size. Finally the intensity of sexual selection in larger species in deer family put them in risk of extinction; but on the other site, small species are more adapted to the environment by choosing different strategy in mating system, reducing antler and body size thus diminishing the extinction risk.
This study is accomplished to fulfil the requirements of the Master of Science degree within Department of Biology at Uppsala University. I would like to specially thank my supervisor, Jacob Höglund for his advices and guidance also many thanks to lecturers in the Biology department. Also special thanks to Olof Pihl who assisted me in editing.
Abril, V.V., Carnelossi, E.A.G.., González, S., and Duarte, J.M.B. 2010. Elucidating the Evolution of the Red Brocket Deer Mazama americana Complex (Artiodactyla; Cervidae). Cytogenetic and Genome Research 2010; 128:177–187.
Abril, V.V., and Duarte, J.M.B. 2008. Mazama nana. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 25th September 2012. http://www.iucnredlist.org/details/29621/0
Amato, G., Egan, M.G.., and Rabinowitz, A. 1999. A new species of muntjac, Muntiacus putaoensis (Artiodactyla: Cervidae) from northern Myanmar. Animal Conservation 2, 1–7
Amato, G., Egan, M.G., Schaller, G.B., Baker, R.H., Rosenbaum, H.C., Robichaud, W.G., and DeSalle, R.
1999.Rediscovery of Roosevelt's Barking Deer (Muntiacus rooseveltorum). Mammalogy, Vol. 80, No. 2, pp. 639-643 Anderson, A. E., and Wallmo, O. C. 1984.Odocoileus hemionus. Mammalian Species, No. 219, pp. 1-9
Andersson, M., and Simmons, L. W. 2006. Sexual selection and mate choice. TRENDS in Ecology and Evolution Vol.21 No.6
Apollonio, M., Focardi, S., Toso, S., and Nacci, L. 1998. Habitat Selection and Group Formation Pattern of Fallow Deer
Dama dama in aSubmediterranean Environment. Ecography, Vol. 21, No. 3, pp. 225-234
APUS. 2003-2013. Accessed on 22nd March 2013.
Asher, G.W., Berg, D.K., Beaumont, S., Morrow, C.J., O’Neill, K.T., Fisher, M.W. 1996. Comparison of seasonal changes in reproductive parameters of adult male European fallow deer ( Dama dama dama) and hybrid Mesopotamian X European fallow deer ( D. d. mesopotamica X D. d. dama). Animal Reproduction Science 45, 201-215
Aung, M., McShea, W.J., Htung, S., Than, A., Soe, T.M., Monfort, S.,and Wemmer, C. 2001. Ecology and Social Organization of a Tropical Deer (Cervus eldi thamin). Journal of Mammalogy, Vol. 82, No. 3, pp. 836-847
Balakrishnan, C.N., MONFORT, S.L., GAUR, A., SINGH, L., and SORENSON, M.D. 2003. Blackwell Publishing, Ltd Phylogeography and conservation genetics of Eld’s deer (Cervus eldi). Molecular Ecology 12, 1-10
Barboza, P. S., Hartbauer, D.W., Hauer W.E., and Blake, J.E. 2004. Polygynous mating impairs body condition and homeostasis in male reindeer (Rangifer tarandus tarandus). Journal of Comp Physiol B,174: 309–317
Barrette, C. 1977. Scent-marketing in captive Muntjacs, Muntiacus reevesi. Anim . Behav., 25, 536-541
Barrio, J., and Tirira, D. 2008. Pudu mephistophiles. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 29th September 2012.http://www.iucnredlist.org/details/18847/0
Bartalucci, A., and Weinstein, B. 2000. "Alces americanus" (On-line), Animal Diversity Web. Accessed on 29th October
Bartosˇ, L., Fricˇova, B., Bartosˇova´ -Vı´chova´, J., Panama´, J., Sˇustr, P., and Sˇmı´dova, E. 2007. Estimation of the Probability of Fighting in Fallow Deer (Dama dama) During the Rut. Aggressive behavior, Volume 33, pages 7–13 Bartoš, L., Reyes, E., Schams, D., Bubenik, G., and Lobos, A. 1998. Rank dependent seasonal levels of IGF-1, cortisol and reproductive hormones in male pudu (Pudu puda). Comparative Biochemistry and Physiology Part A 120, 373–378 Bartoš, L., Schams, D., Bubenik, G.A., Kotrba, R., Tománek, M. 2010. Relationship between rank and plasma
testosterone and cortisol in red deer males (Cervus elaphus). Physiology & Behavior 101, 628–634
Bello, J., Reyna, R., and Schipper, J. 2008. Mazama temama. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. Accessed on 30th October 2012. http://www.iucnredlist.org/details/136290/0
Bowyer, R. T., Rachlow, J. L., Stewart, K. M., and Ballenberghe, V.V. 2011. Vocalizations by Alaskan moose: female incitation of male aggression. Behav Ecol Sociobiol, 65:2251–2260
Bowyer, R. T., Stewart, K. M., Kie, J. G., and Gasaway, W. C. 2001. Fluctuating Asymmetry in Antlers of Alaskan Moose: Size Matters. Journal of Mammalogy, Vol. 82, No. 3, pp. 814-824
Breitenbach, E. 2011. "Muntiacus truongsonensis" (On-line), Animal Diversity Web. Accessed on 7th November 2012.
Bro-Jørgensen, J. 2007. The Intensity of Sexual Selection Predicts Weapon Size in Male Bovids. Evolution, Vol. 61, No. 6, pp. 1316-1326
Brown, C. 2002. "Rusa unicolor" (On-line), Animal Diversity Web. Accessed on 5th October 2012.
Bubenik, G.A., Brown, R.D., and Schams, D. 1991. Antler cycle and endocrine parameters in male axis deer (Axis axis): seasonal levels of LH, FSH, testosterone, and prolactin and results of GnRH and ACTH challenge tests. Camp.
Biochem. Physiol. Vol. 99A, No. 4, pp. 645-650
Bubenik, G. A., Reyes, E., Schams, D., Lobos, A., Bartos, L., and Koerner, F. 2002.Effect of Antiandrogen Cyproterone Acetate on the Development of the Antler Cycle in Southern Pudu (Pudu puda). Journal of experimental zoology 292:393–401
CAB Direct. 2010. Brazilian dwarf brocket deer (Mazama nana). Accessed on 29th September 2012.
Calderon, E. L. 2013. Creatures of the Amazon, Amazonian Brown Brocket. Copyright 2013 Iquitos Times, Lalo Calderon firstname.lastname@example.org. Accessed on 27th March 2013. http://www.iquitostimes.com/brown-brocket.htm
Candolin, U. 1999. Male-Male Competition Facilitates Female Choice in Sticklebacks. Biological Sciences, Vol. 266, No. 1421, pp. 785-789
Candolin, U. 2003. The use of multiple cues in mate choice. Biol. Rev., 78, pp. 575–595
Castillo, R. C. d., and Núñez-Farfán J. 2008. The Evolution of Sexual Size Dimorphism: The Interplay between Natural and Sexual Selection. Journal of Orthoptera Research, Vol. 17, No. 2, Body Size in Orthoptera, pp.197-200
Chan, J.P-W., Tsai, H-Y., Chen, C-F., Tung, K-C., and Chang, C-c. 2009. The reproductive performance of female Formosan sambar deer (Cervus unicolor swinhoei) in semi-domesticated herds. Theriogenology 71, 1156–1161 Costa, K. L. C., da Matta, S. L. P., Gomes, M. de L. M., de Paulac, T. A. R., de Freitas, K. M., Carvalho, F. de A. R., Silveira, J. de A., Dolder, H., and Mendis-Handagama, S.M.L. C. 2011. Histomorphometric evaluation of the neotropical brown brocket deer Mazama gouazoubira testis, with an emphasis on cell population indexes of spermatogenic yield. Animal Reproduction Science 127 202– 212.
Danilkin, A.A. 1995. Capreolus pygargus. Mammalian Species, No. 512, pp. 1-7
Darwin, C., M.A., F.R.S., and c. 1859. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 1872 London: John Murray. 6th edition; with additions and corrections. Eleventh thousand. Albemarle str. 465 pp.
Darwin, C., M.A., F.R.S., and c. 1971. The descent of man and selection in relation to sex. in two volumes_VoL.I. London: John Murray, Albemarle Str.1871. 900 pp.
David's Deer in China. Wildlife Society Bulletin, Vol. 28, No. 3, pp. 681-687
De Bord, D. 2009. "Alces alces" (On-line), Animal Diversity Web. Accessed on 30th October 2012.
Delaney, K. J., Roberts, J. A., and Uetz, G. W. 2007. Male Signaling Behavior and Sexual Selection in a Wolf Spider (Araneae: Lycosidae): A Test for Dual Functions. Behavioral Ecology and Sociobiology, Vol. 62, No. 1, pp. 67-75 D'Elia, G. 1999. "Ozotoceros bezoarticus" (On-line), Animal Diversity Web. Accessed on 2nd November 2012.
Deuling, S. 2004. "Muntiacus reevesi" (On-line), Animal Diversity Web. Accessed on 27th October, 2012.
Dhungel, S. K., and O'Gara, B. W. 1991. Ecology of the Hog Deer in Royal Chitwan National Park, Nepal. Wildlife
Monographs, No. 119, pp. 3-40
Doherty, P. F., Jr., Sorci, G., Royle, J. A., Hines, J.E., Nichols, J.D., and Boulinier. T. 2003. Sexual selection affects local extinction and turnover in bird communities. PNAS, vol.100 10, 5858-5862
Dolev, A., Saltz, D., Bar-David, S., and Yom-Tov, Y. 2002. Impact of Repeated Releases on Space-Use Patterns of Persian Fallow Deer. The Journal of Wildlife Management, Vol. 66, No. 3, pp. 737-746
Dong, w. 2007. New material of Muntiacinae (Artiodactyla, Mammalia) from the Late Miocene of the northeastern Qinghai-Tibetan Plateau, China. C. R. Palevol 6 335–343
Duarte, J.M.B 2008. Mazama bororo. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. Accessed on 27th October 2012.http://www.iucnredlist.org/details/41023/0
Duarte, J.M.B., Varela, D., Piovezan, U., Beccaceci, M.D., and Garcia, J.E. 2008. Blastocerus dichotomus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 21st September 2012.
Durate, J.M.B., Vogliotti, A., and Barbanti, M. 2008. Mazama americana. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 22nd September 2012. http://www.iucnredlist.org/details/29619/0
Dubost, G., Charron, F., Courcoul, A., and Rodier, A. 2011. The Chinese water deer, Hydropotes inermis—A fast growing and productive ruminant. Mammalian Biology 76 190–195
Duckworth, J.W., Kumar, N.S., Anwarul Islam, Md., Hem Sagar Baral, and Timmins, R.J. 2008. Axis axis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 30th September
Duckworth, J.W., Robichaud, W.G., and Timmins, R.J. 2008. Rucervus schomburgki. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. Accessed on 30th October 2012. http://www.iucnredlist.org/details/4288/0
Duckworth, J.W., Samba Kumar, N., Chiranjibi Prasad Pokheral, Sagar Baral, H., and Timmins, R.J. 2008. Rucervus
duvaucelii. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 2nd October 2012.http://www.iucnredlist.org/details/4257/0
Dunn, P.O., Whittingham, L.A., and Pitcher, T.E. 2001. Mating system sperm competition, and the evolution of sexual dimorphism in birds. Evolution, 55(1), pp. 161-175
Durrant, B.S., Oosterhuis, J.E., Johnson, L., Plotka, E.D., Harms, P. G., and Welsh Jr., T.H. 1996. Effect of Testosterone Treatment on the Antler Cycle of an Indian Hog Deer (Cervus porcinus) with Low Endogenous Level of Testosterone.
Journal of Zoo and Wildlife Medicine, Vol. 27, No. 1, pp. 76-82
Easty, L. K., Schwartz, A. K., Gordon, S. P., HendryA. P. 2011. Does sexual selection evolve following introduction to new environments? Animal Behaviour 82 1085e1095
Ehler, P. 2002. "Przewalskium albirostris" (On-line), Animal Diversity Web. Accessed on 1st October, 2012.
Emlen, D.G. 2001. Costs and the Diversification of Exaggerated Animal Structures. Science, New Series, Vol. 291, No. 5508, pp. 1534-1536
Epps, C. 2000. "Blastocerus dichotomus" (On-line), Animal Diversity Web. Accessed on 21st September 2012.
ESRI Inc. 1999. ArcMap TM 9.3. ESRI, 380 New York Street, Redlands, CA 92373-8100, USA
Faivre, B., Grégoire, A., Préault, M., Cézilly, F., and Sorci, G. 2003. Immune Activation Rapidly Mirrored in a Secondary Sexual Trait. Science, New Series, Vol. 300, No. 5616, p. 103
Feldhamer, G.A. 1980. Cervus nippon. Mammalian Species, No. 128, pp. 1-7
Feldhamer, G. A., Farris-Renner, K.C., and Barker, C.M. 1988. Dama dama. Mammalian Species, No. 317, pp. 1-8 Fiorillo, B.F., Sarria-Perea, J.A., Abril, V.V., Duarte, J.M.B. 2013. Cytogenetic description of the Amazonian brown brocket Mazama nemorivaga (Artiodactyla, Cervidae). CompCytogen 7 1: 25–31
Flatt, T. 2011. Survival costs of reproduction in Drosophila. Experimental Gerontology 46 369–375 Franzmann, A. W. 1981. Alces alces. Mammalian Species, No. 154, pp. 1-7
Ferraino, A. 2007. "Rucervus duvaucelii" (On-line), Animal Diversity Web. Accessed on 2nd October, 2012.
Fisher, R.A. 1930.The Genetical Theory of Natural Selection: A Complete Variorum Edition. Edited with an introduction and notes by Henry Bennett. Oxford University Press, Oct 21, 1999 - Mathematics - 318 pages
Fraser, K.W 1996. Comparative Rumen Morphology of Sympatric Sika Deer (Cervus nippon) and Red Deer (C.elaphus
scoticus) in the Ahimanawa and Kaweka Ranges, Central North Island, New Zealand. Oecologia, Vol. 105, No. 2
Gaillard, J. M., Delorme, D., and Jullien, J. M. 1993. Effects of Cohort, Sex, and Birth Date on Body Development of Roe Deer (Capreoluscapreolus) Fawns. Oecologia, Vol. 94, No. 1, pp. 57-61
Gayon, j. 2010. Sexual selection: Another Darwinian process. C. R. Biologies 333 134–144
Geist, V. 1998. Deer of the World: Their Evolution, Behaviour, and Ecology. Stackpole Books publication. 5067 Ritter road, Mechanicsburg, PA 17055. pp. 119–121. First edition.
Giao, P.M., Tuoe, D., Dung, V.V., Wikramanayake, E.D., Amatio, G., Arctander, P., and MacKinnon, J.R. 1998. Describtion of Muntiacus truongsonensis, a new species of muntjac (Artiodactyla: Muntiacidae) from Central Vietnam and implication for conservation. Animal conservation 1, 61-68
Gibson, R.M., and Guinness, F.E. 1980. Behavioural factors affecting male reproductive Success in the red deer (Cervus
elaphus). Anirn. Behav., 28, 1163-1174
Gilbert, C., Ropiquet, A., and Hassanin, A. 2006. Mitochondrial and nuclear phylogenies of Cervidae (Mammalia, Ruminantia): Systematics, morphology, and biogeography. Molecular Phylogenetics and Evolution 40 101–117 Godin, J-G. J., and Briggs, S. E. 1994. Female mate choice under predation risk in the guppy. Anim. Behav., 51, 117– 130
González, S., Álvarez-Valin F., and Maldonado, J. E. 2002. Morphometric Differentiation of Endangered Pampas Deer (Ozotoceros bezoarticus), with Description of New Subspecies from Uruguay. Journal of Mammalogy, Vol. 83, No. 4, pp. 1127-1140
Gonzales, S., Maldonado, J.E., Ortega, J., Talarico, A.C., Bidegaray-Batista, L., Garcia, J. E., and Barbantiduarte, J.M. 2009. Identification of the endangered small red brocket deer (Mazama bororo) using noninvasive genetic techniques (Mammalia; Cervidae).Molecular Ecology Resources 9, 754–758
Gonzalez, T., and Tsytsulina, K. 2008. Capreolus pygargus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1.Accessed on 20th September 2012. http://www.iucnredlist.org/details/42396/0
Goss, R.J. 1983. Deer antlers: regeneration, function, and evolution. Division of biology and medicine, Brown University, Providence, Rhode Island. Illustrated by Wendy Adrews. Academic Press, 111 Fifth Avenue, New York 10003.
Greenwood, P.J. 1980. Mating system, philopatry and dispersal in birds and mammals. Anim. Behav., 28, 1140-1i62 Griffith, S. C., and Sheldon, B. C. 2001. Phenotypic plasticity in the expression of sexually selected traits: neglected components of variation. ANIMAL BEHAVIOUR, 61, 987–993
Groves, C., and Grubb, P. 2011. Ungulate Taxonomy. JHU Press, Nov 1, 2011, 317 pp. Johns Hopkins University press. 2715 North Charles Street, Baltimore, Maryland
Hall, M. D., Bussière, L. F., Hunt, J., and Brooks, R. 2008. Experimental Evidence That Sexual Conflict Influences the Opportunity, Form and Intensity of Sexual Selection. Evolution, Vol. 62, No. 9, pp. 2305-2315
Harris, R.B. 2008. Cervus nippon. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 5th October 2012. http://www.iucnredlist.org/details/41788/0
Harris, R.B. 2008. Muntiacus crinifrons. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 13th October 2012. http://www.iucnredlist.org/details/13924/0
Harris, R.B. 2008. Przewalskium albirostris. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 1st October 2012.http://www.iucnredlist.org/details/4256/0
Harvey, P.H., and Pagel, M.D. 1991. The comparative method in evolutionary biology. Oxford University Press, Oxford 239 pp.
Hastings, B.E., Stadler, S.G., and Kock, R.A. 1998. Reversible Immobilization of Chinese Water Deer (Hydropotes
inermis) with Ketamine and Xylazine. Zoo and Wildlife Medicine, Vol. 20, No. 4, pp. 427-431
Hedges, S., Duckworth, J.W., Timmins, R.J., Semiadi, G., and Priyono, A. 2008. Rusa timorensis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 5th October
Hemami, M.R., Watkinson, A.R., and Dolman, P.M. 2004. Habitat selection by sympatric muntjac (Muntiacus reevesi) and roe deer (Capreolus capreolus) in a lowland commercial pine forest. Forest Ecology and Management, 194 49–60 Henttonen, H., and Tikhonov, A. 2008. Rangifer tarandus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 29th September 2012. http://www.iucnredlist.org/details/29742/0
Holland, B., and Rice, W. R. 1999. Experimental removal of sexual selection reverses intersexual antagonistic coevolution and removes a reproductive load. Evolution Vol. 96, pp. 5083–5088,
Holand, Ø., Weladji, R.B., Røed, K.H., Gjøstein, H., Kumpula, J., Gaillard, J.-M., Smith, M.E., and Nieminen, M. 2007. Male age structure influences females’ mass change during rut in a polygynous ungulate: the reindeer (Rangifer
tarandus). Behav. Ecol. Sociobiol 59: 682–688
ICMBio, Instituto Chico Mendes. De Conservacao da Biodiversidade. 2013. SUMÁRIO EXECUTIVO DO PLANO DE AÇÃO NACIONAL PARA A CONSERVAÇÃO DOS CERVÍDEOS AMEAÇADOS DE EXTINÇÃO. EQSW 103/104, Bloco “C”, Complexo Administrativo, Setor Sudoeste CEP 70.670-350 Brasilia – DF 61 3341-9101
Isaac, N.J.B., Turvey, S.T., Collen, B., Waterman, C., and Baillie, J.E.M. 2007. Mammals on the EDGE: Conservation Priorities Based on Threat and Phylogeny. PLoS ONE 2(3): e296.
IPAM. THE AMAZON ENVIRONMENTAL RESEARCH INSTITUTE.1996. Accessed on 15th December 2012.
Jackson, A. 2002. "Muntiacus muntjak" (On-line), Animal Diversity Web. Accessed on 13th October 2012.
Jackson, J.E. 1987.Ozotoceros bezoarticus. Mammalian Species, No. 295, pp. 1-5
Jacobson, E. 2003. "Elaphurus davidianus" (On-line), Animal Diversity Web. Accessed on 7th October, 2012.
Jansa, S. 1999. "Mazama americana" (On-line), Animal Diversity Web. Accessed on 4th November 2012.
Jetzer, A. 2007. "Muntiacus atherodes" (On-line), Animal Diversity Web. Accessed on 10th October 2012.
Jiang, Z., Yu, C., Feng, Z., Zhang, L., Xia, J., Ding, Y., and Lindsay, N. 2000. Reintroduction and Recovery of Père Jimenez, J., and Ramilo, E. 2008. Pudu puda. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 29th September 2012.http://www.iucnredlist.org/details/18848/0
Jiménez, J., Guineo, G., Corti, P, Smith, J.A., Flueck, W., Vila, A., Gizejewski, Z., Gill, R., McShea, B., and Geist, V. 2008. Hippocamelus bisulcus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 21st
September 2012. http://www.iucnredlist.org/details/10054/0
Jog, M.M., Marathe, R.R., Goel, S.S., Ranade, S.P., Kunte, K.K., and Watve, M.G. 2005. Sarcocystosis of Chital (Axis
axis) and dhole (Cuon alpinus): ecology of a mammalian prey-predator-parasite system in Peninsular India.Journal of Tropical Ecology 21:479-482.
Johansson, A., and Liberg, O. 1996. MammalogistsFunctional Aspects of Marking Behavior by Male Roe Deer (Capreolus capreolus). Journal of Mammalogy, Vol. 77, No. 2, pp. 558-567
Johansson, A., Liberg, O., and Wahlström, L. K. 1995. Temporal and Physical Characteristics of Scraping and Rubbing in Roe Deer (Capreolus capreolus). Journal of Mammalogy, Vol. 76, No. 1, pp. 123-129
Julia, J. P., and PERIS, S. J. 2010. Do precipitation and food affect the reproduction of brown brocket deer Mazama gouazoubira (G. Fischer 1814) in conditions of semi-captivity?Anais da Academia Brasileira de Ciências, 82 3: 629-635
Katopodes, D. 1999. "Hydropotes inermis" (On-line), Animal Diversity Web. Accessed on 2nd November 2012.
Key, N. 2003. "Rusa alfredi" (On-line), Animal Diversity Web. Accessed on 2nd October, 2012.
Koga, T., and Ono, Y. 1994. Sexual Differences in Foraging Behavior of Sika Deer, Cervus Nippon. Journal of
Mammalogy, Vol. 75, No. 1, pp. 129-135
Kokko, H., and Brooks, R. 2003. Sexy to die for? Sexual selection and the risk of extinction. Ann. Zool. Fennici, 40: 207-219
Kolm, N., Stein, R. W., Mooers, A. Ø., Verspoor, J. J., and Cunningham, E. J. A. 2007. Can sexual selection drive female life histories? A comparative study on Galliform birds. THE AUTHORS 20 627–638
Kufner, M.B., Sepu´lveda, L., Gavier, G., Madoery, L., and Giraudo, L. 2008. Is the native deer Mazama gouazoubira threatened by competition for food with the exotic hare Lepus europaeus in the degraded Chaco in Co´rdoba, Argentina? Journal of Arid Environments 72: 2159–2167
Landesman, N. 1999. "Cervus nippon" (On-line), Animal Diversity Web. Accessed on 7th November 2012.
La Otra Opcion A.C. Reserva Ecologica. 2010. Brockett Deer (Mazamma temama). Accessed on 27th March 2013.
Leasor, H., Chiang, P.J., and Pei, K.J-C. 2008. Muntiacus reevesi. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2.Accessed on 27th October 2012. http://www.iucnredlist.org/details/42191/0
Lizcano, D. J., and Alvarez, S. J. 2008. Mazama bricenii. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 23 September 2012. http://www.iucnredlist.org/details/136301/0
Lizcano, D., and Alvarez, S.J. 2008. Mazama rufina. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 29th September 2012.http://www.iucnredlist.org/details/12914/0
Lovari, S., Herrero. J., Conroy, J., Maran, T., Giannatos, G., Stubbe, M., Aulagnier, S., Jdeidi, T., Masseti, M. Nader, I., de Smet, K., and Cuzin, F. 2008. Cervus elaphus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. Accessed on 4th October 2012. http://www.iucnredlist.org/details/41785/0
Lovin the outdoors. Wednesday 11 August 2009. World's Smallest Deer. Accessed on 5th April 2013.