Abstract
Recent climatic models suggest the late Pleistocene was colder and had different precipitation regimes from the present. If this climatic shift occurred more rapidly than species could adapt, species likely shifted their ranges as populations moved in concert with suitable environmental conditions. We examined changes in altitudinal and horizontal distribution in response to past climate change of amphibian species from different elevational zones and habitat requirements in the Eastern Cordillera of the Colombian Andes. We used environmental information and species occurrence data to model the distribution of 14 amphibian species (seven highland and seven lowland) which we projected to the Last Glacial Maximum (LGM) using two past climatic reconstructions. For these 14 species, we studied the predicted elevational and areal shifts. In agreement with palynological-derived models for Andean flora, we predicted that the elevation of montane amphibians shifted downwards increasing their total altitudinal range. We did not detect any evidence of compression related to drier lowlands. In some cases, the wider distribution areas of high-elevation amphibians during the LGM overlapped with contemporary distributions implying that these areas are present-day refugia for some species. Lowland species showed little or no elevational changes across time, but their areal distributions changed depending on habitat requirements. Four lowland frog species occurring in present-day xeric environments showed substantial range expansion across the lowlands during the LGM, while two species occurring in humid habitats likely expanded their ranges since the LGM. Since the LGM ended, ranges of mid‐ to high-elevation species shrank and shifted to higher elevation. Lowland species in xeric or open habitats have also experienced shrinking ranges, with some evidence that they have been moving upwards. Thus, low- and high-elevation species may be at risk under predicted anthropogenic climate change. Our results generate spatial hypotheses about amphibian responses to climate change that can be tested with phylogeographic data.
Highlights
Climatic fluctuations can have dramatic impacts on species’ distribution and survival
To predict how frog species with contrasting elevational ranges and habitat preferences may have differentially responded to Pleistocene climate changes, we focused on 14 species from the Eastern Cordillera of the Colombian Andes that had at least 7 locality records to proceed with the generation of distribution models (Hernandez et al 2006, Pearson et al 2007)
When grouping elevational data by species’ altitudinal distribution (7 highland species together and 7 lowland species together), we found significant change in median altitude by comparing the Last Glacial Maximum (LGM) versus the present in highland and lowland species, shifting downwards at the LGM [Kruskal-Wallis tests with P-value < 2.2 × 10-16 for both highland and lowland species and post-hoc tests with all three comparisons significantly different (CCSM vs. Model for Interdisciplinary Research on Climate (MIROC), Community Climate System Model (CCSM) vs. present, and MIROC vs. present), Fig. 3]
Summary
Climatic fluctuations can have dramatic impacts on species’ distribution and survival. In the face of global climate fluctuations, some areas may have remained stable such that populations may have persisted without the need to move or adapt to new conditions These temporally stable and geographically isolated pockets of suitable habitat are known as ‘refugia’ (Haffer 1969, Gavin et al 2014). The Pleistocene refugia hypothesis states that reduced precipitation during glacial maxima reduced the extent of lowland wet-forest environments, restricting wet-forest species to refugia isolated by a matrix of open, drier habitat (Haffer 1969) During interglacial times, such as the present day, these wet-forest species are expected to have larger ranges relative to their distribution during glacial periods (Waltari et al 2007). While some evidence exists for expansion of xeric-habitat species during the LGM (Quijada‐Mascarenas et al 2007), palynological and molecular evidence in support of the predictions of Pleistocene refugia for wet-forest species is equivocal (Colinvaux 1996, Lessa et al 2003)
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