The genetic make-up of an organism is what we rely on to distinguish between different species. Animals clustered together on a genetic scale are considered to belong to the same taxonomic group, while those most dissimilar from each other belong to different taxa. Nonetheless, even within a taxonomic group there is a certain degree of genetic diversity which is key for wild populations to be able to respond and adapt effectively to an ever-changing environment – and which is ultimately what allows populations to persist rather than perish. On this note, conservationists aim to preserve high levels of intraspecific genetic diversity.
Considering the significant extent of anthropogenic influence that we had and keep having on the planet, there is a high risk that we may be driving intraspecific genetic diversity down, impacting the natural resilience of species to environmental change, and ultimately making wildlife populations more vulnerable to extinction. A new study led by researchers Katie Millette and Vincent Fugère based at the University of Montreal, Canada, set out to investigate this issue. However, in their paper published in Ecology Letters, the team could not find any consistent effects of humans on animal genetic diversity worldwide, within the 1980-2016 period1.
While insect and fish populations were found to have lower intraspecific diversity in areas with high human densities, the authors say that it remains unclear whether that was because species that colonise human-altered habitats lose their intraspecific diversity or have naturally lower diversity than species unable to persist in such environments.
Spatial variation in COI nucleotide diversity of birds, inland and coastal bony fishes, insects and mammals. Diversity values are GAMM predictions when assuming that all sequences from a given population were collected at the same location, thus removing the confounding effect of population spatial extent on nucleotide diversity. Note that diversity scales differ among animal classes. Figure and description credits: Millette et al. (2019)
Discussing their results, the authors say that in all their analyses “the direction and magnitude of human effects on intraspecific genetic diversity were taxon-dependent and either non-significant or weak, even at small spatial scales.” Similarly, they found little evidence of temporal changes in intraspecific genetic diversity.
Nevertheless, anthropogenic activity is likely to have complex effects on intraspecific genetic diversity and these may also vary largely between different taxa. This makes it challenging for researchers to accurately define our impact on animal genetic diversity. Further research is needed on this front, the authors conclude.
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- Millette, K. L., Fugère, V. , Debyser, C. , Greiner, A. , Chain, F. J. and Gonzalez, A., 2019. No consistent effects of humans on animal genetic diversity worldwide. Ecol Lett. https://doi.org/10.1111/ele.13394