Abstract
We evaluated if two sigmodontine rodent taxa (Abrothrix olivacea and Phyllotis darwini) from the Andes and Coastal mountaintops of central Chile, experienced distributional shifts due to altitudinal movements of habitat and climate change during and after the Last Glacial Maximum (LGM). We tested the hypothesis that during LGM populations of both species experienced altitudinal shifts from the Andes to the lowlands and the coastal Cordillera, and then range retractions during interglacial towards higher elevations in the Andes. These distributional shifts may have left remnants populations on the mountaintops. We evaluated the occurrence of intraspecific lineages for each species, to construct distribution models at LGM and at present, as extreme climatic conditions for each lineage. Differences in distribution between extreme climatic conditions were interpreted as post-glacial distributional shifts. Abrothrix olivacea displayed a lineage with shared sequences between both mountain systems, whereas a second lineage was restricted to the Andes. A similar scenario of panmictic unit in the past was recovered for A. olivacea in the Andes, along with an additional unit that included localities from the rest of its distribution. For P. darwini, both lineages recovered were distributed in coastal and Andean mountain ranges at present as well, and structuring analyses for this species recovered coastal and Andean localities as panmictic units in the past. Niche modeling depicted differential postglacial expansions in the recovered lineages. Results suggest that historical events such as LGM triggered the descending of populations to Andean refuge areas (one of the A. olivacea’s lineages), to the lowlands, and to the coastal Cordillera. Backward movements of populations after glacial retreats may have left isolates on mountaintops of the coastal Cordillera, suggesting that current species distribution would be the outcome of climate change and habitat reconfiguration after LGM.
Highlights
The Pleistocene, the last .9 Mya, characterized by worldwide climatic changes associated with glacial cycles that increased in amplitude, forcing species to shift their ranges, and subsequently impacting the structure of their populations
We observe that for both species there is a higher number of haplotypes in the Andes than in the coast, which is remarkably notorious for P. darwini (Table 1); at the same time the haplotype diversity (Hd) is higher in the Andes mountains than in the coast for both species
For A. olivacea we observed that one of the phylogroups is restricted to Andean localities, while the other is distributed in both mountain ranges, some in the valley and some in coastal localities
Summary
The Pleistocene, the last .9 Mya, characterized by worldwide climatic changes associated with glacial cycles that increased in amplitude, forcing species to shift their ranges, and subsequently impacting the structure of their populations. Mya, characterized by worldwide climatic changes associated with glacial cycles that increased in amplitude, forcing species to shift their ranges, and subsequently impacting the structure of their populations. There have been studies proposing that under glacial-dominated scenarios, species at higher latitudes experienced strong demographic and genetic changes in their populations [1]. In South America, Pleistocene glacial events would have had severe effects on populations associated with Andean mountains, where ice sheets and permafrost were focused on the southern cone of the continent [4,5,6,7]. Populations inhabiting higher latitudes would have suffered local extinctions, expansions and retractions following Quaternary glacial oscillations [2,8,9]
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