Abstract
A primary goal of biogeography is to understand how large‐scale environmental processes, like climate change, affect diversification. One often‐invoked but seldom tested process is the “species‐pump” model, in which repeated bouts of cospeciation are driven by oscillating climate‐induced habitat connectivity cycles. For example, over the past three million years, the landscape of the Philippine Islands has repeatedly coalesced and fragmented due to sea‐level changes associated with glacial cycles. This repeated climate‐driven vicariance has been proposed as a model of speciation across evolutionary lineages codistributed throughout the islands. This model predicts speciation times that are temporally clustered around the times when interglacial rises in sea level fragmented the islands. To test this prediction, we collected comparative genomic data from 16 pairs of insular gecko populations. We analyze these data in a full‐likelihood, Bayesian model‐choice framework to test for shared divergence times among the pairs. Our results provide support against the species‐pump model prediction in favor of an alternative interpretation, namely that each pair of gecko populations diverged independently. These results suggest the repeated bouts of climate‐driven landscape fragmentation have not been an important mechanism of speciation for gekkonid lizards across the Philippine Archipelago.
Highlights
Understanding how environmental changes affect diversification is an important goal in evolutionary biology, biogeography, and global change biology
The Philippine archipelago represent such a model system, with more than 7,100 islands that arguably harbor the highest concentration of terrestrial biodiversity on Earth (Catibog-Sinha and Heaney, 2006; Brown and Diesmos, 2009; Heaney and Regalado, 1998; Brown et al, 2013); how, when, and by which mechanisms this diversity accumulated has piqued the interest of evolutionary biologists since the early development of the field of biogeography (Wallace, 1869; Huxley, 1868; Dickerson, 1928; Diamond and Gilpin, 1983; Brown, 2016; Lomolino et al, 2016)
During lower sea levels of glacial periods, islands coalesced into seven major landmasses (PAICs) that were fragmented into individual islands during interglacial periods
Summary
Understanding how environmental changes affect diversification is an important goal in evolutionary biology, biogeography, and global change biology. During lower sea levels of glacial periods, islands coalesced into seven major landmasses (PAICs) that were fragmented into individual islands during interglacial periods. These climate-driven cycles have occurred at least six times during the last 500,000 years (Rohling et al, 1998; Siddall et al, 2003; Spratt and Lisiecki, 2016), with additional cycles occurring in the late Pliocene and early Pleistocene (Haq et al, 1987; Miller et al, 2005)
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