You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Return flight to the Canary Islands - The key role of peripheral populations of Afrocanarian blue tits (Aves: Cyanistes teneriffae) in multi-gene reconstructions of colonization pathways. Afrocanarian blue tits (Cyanistes teneriffae) have a scattered distribution on the Canary Islands and on the North African continent. To date, the Canary Islands have been considered the species' main Pleistocene evolutionary center, but their colonization pathways remain uncertain. We set out to reconstruct a dated multi-gene phylogeny and ancestral ranges for Cyanistes tit species including the currently unstudied, peripheral Libyan population of C. t. cyrenaicae. In all reconstructions the most easterly and westerly peripheral populations (in Libya and on La Palma) represented basal offshoots of C. teneriffae. These two peripheral populations shared all four major indels and differed in this respect from all other members of the Afrocanarian core group. The basal split of Afrocanarian blue tits from their European relatives was dated to the early Pliocene. The two ancestral area reconstructions were contradictory and suggested either a Canarian or a North African origin of C. teneriffae - but unambiguously ruled out a continental European ancestral range. We conclude that the peripheral populations of C. teneriffae represent relic lineages of a first faunal interchange, presumably downstream colonization from North Africa to the Canary Islands. Subsequent eastward stepping-stone colonization within the Canarian Archipelago culminated in a very recent late (possibly even post-) Pleistocene back-colonization from the Canary Islands to North Africa.
{"Chemical": []}