Abstract
BackgroundEvolutionary studies of insular biotas are based mainly on extant taxa, although such biotas represent artificial subsets of original faunas because of human-caused extinctions of indigenous species augmented by introduced exotic taxa. This makes it difficult to obtain a full understanding of the history of ecological interactions between extant sympatric species. Morphological bill variation of Fringilla coelebs and F. teydea (common and blue chaffinches) has been previously studied in the North Atlantic Macaronesian archipelagos. Character displacement between both species has been argued to explain bill sizes in sympatry. However, this explanation is incomplete, as similar patterns of bill size have been recorded in F. coelebs populations from islands with and without F. teydea.Methodology/Principal FindingsThe discovery of a new extinct species in Tenerife (Canary Islands), here named Carduelis aurelioi n. sp. (slender-billed greenfinch), provides the opportunity to study ancient ecological interactions among Macaronesian finches. To help understand the evolutionary histories of forest granivores in space and time, we have performed a multidisciplinary study combining: (1) morphological analyses and radiocarbon dating (11,460±60 yr BP) of the new taxon and, (2) molecular divergence among the extant finch species and populations in order to infer colonization times (1.99 and 1.09 My for F. teydea and F. coelebs respectively).Conclusion/Significance C. aurelioi, F. coelebs and F. teydea co-habited in Tenerife for at least one million years. The unique anatomical trends of the new species, namely chaffinch-like beak and modified hind and forelimbs, reveal that there was a process of divergence of resource competition traits among the three sympatric finches. The results of our study, combined with the presence of more extinct greenfinches in other Macaronesian islands with significant variation in their beak sizes, suggests that the character displacement has influenced patterns of divergence in bill size and shape on other Macaronesian islands as well.
Highlights
Resource competition between sympatric species can produce morphological differences between those species, often resulting in ecological divergence
Systematic Palaeontology Order Passeriformes Family Fringillidae Genus Carduelis Bisson, 1760 Materials could be attributed to the genus either Carduelis or Serinus based on the following combination of cranial characters: strong and vigorous maxilla and mandible, processus zygomaticus and postorbitalis very well developed, processus palatinus premaxillaris not fused with the palatinum and forming a lateral flange, only one fonticulum orbitale, a single and long foramen orbitonasale, foramen venae occipitalis externae at the posterior edge of foramen magnum, and a long processus orbitalis quadrati
The finding of a new greenfinch species represents the discovery of a new and recently extinct bird, but it provided an unexpected opportunity for studying ancient ecological interactions that have been as yet poorly understood
Summary
Resource competition between sympatric species can produce morphological differences between those species, often resulting in ecological divergence. Evolutionary studies of insular biotas are based mainly on extant taxa, such biotas represent artificial subsets of original faunas because of human-caused extinctions of indigenous species augmented by introduced exotic taxa. This makes it difficult to obtain a full understanding of the history of ecological interactions between extant sympatric species. Morphological bill variation of Fringilla coelebs and F. teydea (common and blue chaffinches) has been previously studied in the North Atlantic Macaronesian archipelagos Character displacement between both species has been argued to explain bill sizes in sympatry. This explanation is incomplete, as similar patterns of bill size have been recorded in F. coelebs populations from islands with and without F. teydea
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