Patterns of genetic variation in anthropogenically impacted populations

Abstract

Genetic variation is considered critical for allowing natural populations to adapt to their changing environment, and yet the effects of human disturbance on genetic variation in the wild are poorly understood. Different types of human disturbances may genetically impact natural populations in a predictable manner and so the aim of this study was to provide an overview of these changes using a quantitative literature review approach. I examined both allozyme and microsatellite estimates of genetic variation from peer-reviewed journals, using the mean number of alleles per locus and expected heterozygosity as standardized metrics. Populations within each study were categorized according to the type of human disturbance experienced (''hunting/harvest'', ''habitat fragmentation'', or ''pollution''), and taxon-specific, as well as time-and context-dependent disturbance effects were considered. I found that human disturbances are associated with weak, but consistent changes in neutral genetic variation within natural populations. The direction of change was dependent on the type of human disturbance experienced, with some forms of anthropogenic challenges consistently decreasing genetic variation from background patterns (e.g., habitat fragmentation), whereas others had no effect (e.g., hunting/ harvest) or even slightly increased genetic variation (e.g., pollution). These same measures appeared sensitive to both the time of origin and duration of the disturbance as well. This suggests that the presence or absence, strength, type, as well as the spatial and temporal scale of human disturbance experienced may warrant careful consideration when conservation management plans are formulated for natural populations, with particular attention paid to the effects of habitat fragmentation.

Population genetics of the hazel hen Bonasa bonasia in Poland assessed with non-invasive samples

“…Molecular indicators of genetic variability were generally higher in subpopulations from continuous habitat than in subpopulations from fragmented habitats, supporting observations for other sedentary grouse species [68,69]. Habitat fragmentation has a much stronger effect on decreases in genetic variability than other forms of human disturbance, such as hunting [70]. Indeed, the allelic richness, heterozygosity, and polymorphism of the mitochondrial control region were lowest in the most spatially isolated subpopulations PF and RF.…”

Genetic erosion in the snailLittoraria subvittata(Reid, 1986) due to mangrove deforestation

“…The loss of genes in these populations can increase the effect of genetic drift, leading to genetic differentiation from unaffected populations (Vandergast et al, 2006;Dibattista, 2008). For example, the low genetic diversity of the endangered crab Uca arcuata on Okinawa may be caused by genetic drift in small populations, in combination with low incoming gene flow from other populations (Aoki et al, 2008).…”

Hidden dispersal in an urban world: genetic analysis reveals occasional long-distance dispersal and limited spatial substructure among Dutch pine martens

“…Decreased size of forest patches may reduce habitat quality and maximum local population sizes of forest dwelling animals, which may increase extinction risks due to both demographic and genetic effects (Fahrig 2003). From a genetic point of view, small populations may show reduced adaptability due to lack of variation, as well as reduced fitness due to inbreeding depression (DiBattista 2008). At the same time, larger distances between patches or the presence of dispersal barriers may reduce connectivity and thereby opportunities for gene flow (Frankham et al 2010).…”