Abstract
BackgroundThe subtropical island of Taiwan is an area of high endemism and a complex topographic environment. Phylogeographic studies indicate that vicariance caused by Taiwan's mountains has subdivided many taxa into genetic phylogroups. We used mitochondrial DNA sequences and nuclear microsatellites to test whether the evolutionary history of an endemic montane bird, Steere's Liocichla (Liocichla steerii), fit the general vicariant paradigm for a montane organism.ResultsWe found that while mountains appear to channel gene flow they are not a significant barrier for Steere's Liocichla. Recent demographic expansion was evident, and genetic diversity was relatively high across the island, suggesting expansion from multiple areas rather than a few isolated refugia. Ecological niche modeling corroborated the molecular results and suggested that populations of Steere's Liocichla are connected by climatically suitable habitat and that there was less suitable habitat during the Last Glacial Maximum.ConclusionsGenetic and ecological niche modeling data corroborate a single history--Steere's Liocichla was at lower density during the Last Glacial Maximum and has subsequently expanded in population density. We suggest that such a range-wide density expansion might be an overlooked cause for the genetic patterns of demographic expansion that are regularly reported. We find significant differences among some populations in FST indices and an admixture analysis. Though both of these results are often used to suggest conservation action, we affirm that statistically significant results are not necessarily biologically meaningful and we urge caution when interpreting highly polymorphic data such as microsatellites.
Highlights
The subtropical island of Taiwan is an area of high endemism and a complex topographic environment
Populations of Steere’s Liocichla have been historically connected by gene flow, though inter-population migration appears largely confined to middle elevations
We found evidence of a demographic expansion that can be dated to the Last Glacial Maximum
Summary
The subtropical island of Taiwan is an area of high endemism and a complex topographic environment. Despite the fact that most biodiversity occurs in tropical areas, most studies have focused on the temperate regions in North America and Europe where the retreat of ice sheets has left widespread genetic patterns consistent with northward expansion from southern refugia [2]. This bias has left us with a poorer understanding of the impact of climate cycles on the phylogeographical patterns of tropical taxa. Mountains have provided additional opportunities for isolation This is reflected in the phylogeographic patterns found in some lowland taxa. The observation of common phylogeographic patterns in such varied taxa suggests vicariance as the cause [13]
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