The shaping of genetic variation in the edge-of-range populations under past and future climate change

As the climate continues to warm because of human influences on the chemical composition of the atmosphere, organisms will need to adapt to new conditions or move to new habitats. While many species have proven able to adjust their ranges when faced with changes in temperature or food availability, the consequences of range-shift have not been widely studied. Razgour et al. studied a species of bat (Plecotus austriacus) in the hopes of better understanding the decreases in genetic diversity that can occur after range shifting caused by climate change. The authors extracted genomic DNA from 259 individuals and conducted various genetic analysis tests on the DNA including PCR. Additional data included genetic diversity information from models of past climate-related range shifts in Europe. The data were combined to predict future declines in genetic diversity for P. austriacus populations in Europe. The study provides evidence that geographical barriers shape genetic variation and that in the future, genetic diversity in P. austriacuswill be reduced by more than half, as it will for many other temperate European species. –Lizzie Medford

Razgour, O., Juste, J., Ibanez, C., Kiefer, A., 2013. The shaping of genetic variation in edge-of- range populations
under past and future climate change. Ecology Letters doi 10.111/ele. 12158

Future changes in temperature and precipitation will not only affect the population sizes of species but may also affect the genetic diversity of different communities by killing off all but a select few individuals in a particular habitat. Studying the genetic diversity of current bat populations can provide insight into how past climate events have shaped genetic diversity. Razgour et al. constructed phylogenetic trees and utilized numerous genetic analysis programs to determine Iberia as the location of the most diverse populations of bats with the greatest number of unique haplotypes and private alleles. This is likely the origin of the species after the Last Glacial Maximum (LGM), which cause range shifts and reduced genetic diversity in the species.
Evidence of past destruction of genetic diversity can be found in fossil records from the past climate changes in Europe following the LGM and receding of the glaciers. Ecological niche modeling and ABC inference of demographic history models were both used to construct a hypothetical range for the bats in the past and future. These studies predicted that most of the current habitat range for the bats would no longer be suitable habitats by 2080. This range restriction will cause more than half of the species’ genetic diversity to be located in unsuitable locations, which will result in vast diversity losses. Additionally, limited contemporary gene flow across the Pyrenees Mountains suggests that geographic barriers like mountains will further restrict the range of P. austriacus.

Razgour et al. studied P. austriacus for the species’ diversity, wide distribution, keystone ecological roles, and sensitivity to changes in temperature. Besides these attributes, bats also have a longevity and reproductive rate that suggest that they may not be able to evolve quickly enough for future changes in temperature and precipitation. The study concludes that the future for these bats will include northern range expansion and southern range contraction by the end of the century. These range shifts will likely cause the most extensive loss of genetic diversity in the most diverse populations. Moreover, this loss of genetic diversity may make the bats more vulnerable to threats like disease and challenges relating to more severe changes climate. Therefore, the authors of this study urge further research into the effects of climate change on leading-edge populations, as they will play a significant role in range shifts and spreading genetic diversity.

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