Biogeography and Diversification of the Andean Seedsnipes (Thinocoridae): An Antarctic Avian Lineage?

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Ibarguchi, Gabriela
Phylogeography , Antarctica , South America , Morphology , Andes , Mountains , Population Genetics , Evolution , Morphometrics , Phylogenetics , Cold , High Altitude , Landscape Genetics , Hemoglobins , Mitochondrial DNA , Environment
South America and the Andes harbour a rich biodiversity. High levels of in-situ speciation, survival of relict lineages into modern times, and mixing of biotas (Gondwanian and North American), have been demonstrated to contribute to the extant biodiversity. Here I examined the four species in the shorebird family Thinocoridae (seedsnipes) as a test case of complementary hypotheses about the origins of this diversity: 1) that some lineages arose from cold-adapted Antarctic ancestors (post-Gondwana), and 2) that the Andes have promoted diversification through vicariance and via the creation of novel alpine niches. First, I reviewed the tectonic and environmental history of the Andes, and the major biogeographic patterns in South America. Second, I reviewed Antarctic and Southern Hemisphere paleoenvironments, putative refugia, colonisation routes, molecular and biogeographic studies, and found strong evidence supporting the role of Antarctica as a source of global cold-hardy biodiversity. Third, I developed universal protocols to purify mitochondrial DNA (mtDNA). Using these methods, I uncovered nuclear pseudogenes, true mtDNA heteroplasmy, and possible hybridisation between seedsnipe lineages. Fourth, I investigated geographic patterns in seedsnipe morphology in four species. I also investigated the relationships of ecogeographic variables related to cold on morphology. I found strong and significant regional differences particularly in the smaller Thinocorus species, including an effect of the high Central Andes. Altitude, latitude, and wind (the effect of cold) have shaped seedsnipe morphology; Thinocoridae as a group generally support Bergmann’s and Allen’s rules. Fifth, based on phylogeographic and phylogenetic analyses of mtDNA and hemoglobin sequences, a putative southern origin for seedsnipes was supported, and an early origin in alpine habitats is suggested. Sixth, I compared data on Andean uplift and glaciation in South America, and found concordance between seedsnipe diversity, known areas of endemism in other taxa, and paleoenvironmental history. Finally, I briefly examined molecular evolution in hemoglobins and mtDNA and found preliminary evidence of adaptations to high altitude (hemoglobins) and to cold (mtDNA and hemoglobins). In summary, an Antarctic ancestor for seedsnipes, pre-adapted for life in the Andes, is supported. Antarctica may have contributed a great proportion of cold-hardy biodiversity to the South and globally.
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