Mountaintops phylogeography: A case study using small mammals from the Andes and the coast of central Chile

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.

Genetic variation of the Chilean endemic long-haired mouseAbrothrix longipilis(Rodentia, Supramyomorpha, Cricetidae) in a geographical and environmental context

“…40°S was proposed for Abrothrix olivacea ( Smith, Kelt & Patton, 2001 ). Recently, Palma et al (2017) suggested for Phyllotis darwini and Abrothrix olivacea postglacial expansion from the lowlands and coastal areas towards the Andes; however, as this study considers a very small fraction of the whole species distributions (i.e., a sampled area restricted to 32° and 33° for species ranging from ca. 23° to 39° and ca.…”

Coupling fossil records and traditional discrimination metrics to test how genetic information improves species distribution models of the European beech Fagus sylvatica

“…While some pioneer studies have already suggested that incorporating genetic information into SDMs improve model performance (Chardon et al, 2020;Palma et al, 2017), others have suggested that it does not improve model accuracy (Collart et al , 2020); Lecocq et al, 2019), thus reopening the debate on whether incorporating genetic information into SDMs can improve our understanding of species distribution. Noteworthy, these studies mainly focused on visual inspections from predicted maps to make comparisons of model performances or used general metrics of model performances (e.g.…”

“…Noteworthy, these studies mainly focused on visual inspections from predicted maps to make comparisons of model performances or used general metrics of model performances (e.g. Palma et al, 2017) systematically relying on presence-only data (Chardon et al, 2020) to validate their models and draw their conclusions, which may limit our abilities to evaluate the performance of geneticallyinformed SDMs. As far as we are aware, no study before ours has specifically tested the ability of genetically-informed SDMs to better explain the abundance of pollen found in the fossil records, providing truly independent evidence that genetically-informed SDMs outperform traditional SDMs in their abilities to detect potential refugia.…”

“…When distinct genetic groups respond differently to environmental variables, modelling those genetic units independently could theoretically provide more reliable predictions of the species response as a whole (Pearman et al, 2010;Peterson, Doak, & Morris, 2018;Smith et al, 2018). Based on those premises, a few studies have arrived at better predictions when modelling lineages independently (Chardon et al, 2020;Lecocq, Harpke, Rasmont, & Schweiger, 2019;Palma, Gutiérrez-Tapia, González, Boric-Bargetto, & Torres-Pérez, 2017;Collart et al, 2020). For two rodent species in the Andes, Palma et al (2017) used SDMs to model each species individually as well as individual lineages separately for each species.…”

“…Based on those premises, a few studies have arrived at better predictions when modelling lineages independently (Chardon et al, 2020;Lecocq, Harpke, Rasmont, & Schweiger, 2019;Palma, Gutiérrez-Tapia, González, Boric-Bargetto, & Torres-Pérez, 2017;Collart et al, 2020). For two rodent species in the Andes, Palma et al (2017) used SDMs to model each species individually as well as individual lineages separately for each species.…”