Perhaps it was marvelling at Zallinger's famous Yale University mural of a Carboniferous landscape as a child that makes me associate tree ferns with an earlier geologic time. It has been guessed that there may be as many as 1,000 living species of these slow-growing giants among the ferns. Because most are limited in their distribution, they are particularly susceptible to deforestation. Considering their height and reproduction based on wind-dispersed spores, such localisation is counterintuitive.
Dr Marcus Lehnert of the Universität Göttingen recently identified four new species of tree fern among the fern flora of Ecuador, already among the richest on Earth. At present, 177 endemic species are known among a total of about 1,300 Ecuadorian species. Insufficient collections and incomplete descriptions of variation have contributed to slow progress in tree fern taxonomy. Some widespread species have been named several times while at the same time new species continue to be discovered.
Dr Lehnert was collecting in the Tapichalaca Reserve in southern Ecuador in the autumn of 2003 when he found a specimen that resembled Cyathea albomarginata. Could it be? If so, this would be a surprising find given that the species in known only from localities 1,500km away in Costa Rica. To be sure, it would be necessary to collect sori, clusters of sporangia, from sexually mature plants. What was key to observe was whether or not there was an indusium, a tiny veil, over the sorus. After additional searching, a fertile plant was found, but at five metres in height it was impossible to reach the upper branches. That required a return trip to the site a year later. The effort was worth it, however, and the species was confirmed to be new. Working within a relatively small range, this and related species were found at several locations.
One of the new species, Cyathea moranii, was named in honour of Robbin C Moran of the New York Botanical Garden, a leading pteridologist and prolific collector and writer. The new species was found in the Zamora-Chinchipe Province at about 2,500m elevation in sheltered side valleys and ravines containing moist montane forest. Trunks of the new species grow to 6m in height and 10cm in diameter and are "clean", petioles dropping off without leaving residual bases behind. Because diagnostic scales and scurf, or small scales, are easily lost in the process of collecting and preparing herbarium specimens of the new species, the potential for confusion among related species is increased.
The continued discovery of new ferns that are small and cryptic is hardly surprising, but tree ferns are large and conspicuous elements of tropical forests. It is precisely their size that makes collecting difficult and results in mere fragments of specimens in collections.
These ferns appear to be genuinely rare and limited in their distribution. Fortunately for them, their complete known range falls within protected areas. In a small note of poetic justice, the Costa Rican C albomarginata with which C moranii was initially confused was named by none other than Dr Robbin Moran.