Contemporary and historic causes of biogeographic gradients in genetic diversity
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Date
2021-04-29
Authors
Schmidt, Chloé
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Abstract
Genetic diversity is the most fundamental level of biodiversity, yet little is known about its broad spatial structure across taxa. Spatial variation in species richness, on the other hand, is the most notable and well-described biogeographic pattern in nature, but our understanding of its causes remains underdeveloped. Linking pattern to process requires shifting focus from the species level to population genetic diversity—the level at which evolution acts. Until recently, it was not possible to incorporate estimates of genome-wide diversity indicative of population processes into analyses of species richness patterns due to a lack of comparable multi-species, population-level data. To address this gap, I compiled publicly archived, raw, neutral, nuclear molecular genetic data to build an aggregated database of metrics of genetic composition in North American terrestrial vertebrates comprised of 99 species (44 mammal, 25 bird, 19 amphibian, and 11 reptile), totaling 58,946 individual genotypes from 1,682 sample sites across the United States and Canada. I hypothesized that these genetic and species levels of biodiversity are closely connected by demographic processes related to environmental carrying capacity determined by environmental energy availability, niche heterogeneity, and habitat loss and fragmentation due to human causes. I used statistical approaches to detect patterns of spatial structure and structural equation modelling to simultaneously analyze environmental effects on genetic and species levels. In general, genetic diversity and population connectivity were consistently negatively affected by habitat degradation both across urban-rural gradients and within urban areas. Accordant with known patterns, species diversity increased with energy and niche availability. Populations tended to have lower genetic diversity and were more genetically differentiated in species richness hotspots. Overall, these results suggest that genetic diversity and species richness are jointly affected by environmental carrying capacity related to historic and contemporary factors, but these relationships do not always hold across taxonomic groups. Understanding the relationships between genetic diversity, species richness, and environments is important because they contribute to ecosystem resilience in changing environments. The wealth of raw genetic data now available is exciting because of the new opportunities for exploring previously hidden levels of biodiversity it brings, and its value as a conservation tool.
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Keywords
Evolutionary ecology, Macrogenetics, Conservation genetics, Biodiversity, Urbanization, Population genetics
Citation
Schmidt, C., Domaratzki, M., Kinnunen R.P., Bowman, J., Garroway, C.J. (2020). Continent-wide effects of urbanization on bird and mammal genetic diversity. Proc. R. Soc. B. 287(1920): 20192497. doi: 10.1098/rspb.2019.2497
Schmidt, C., Garroway, C.J. (2021). The conservation utility of mitochondrial genetic diversity in macrogenetic research. Conserv. Genet. doi: 10.1007/s10592-021-01333-6
Schmidt, C., Garroway, C.J. (2021). The conservation utility of mitochondrial genetic diversity in macrogenetic research. Conserv. Genet. doi: 10.1007/s10592-021-01333-6