Abstract
Bachman's Sparrow (Peucaea aestivalis) is a fire-dependent species that has undergone range-wide population declines in recent decades. We examined genetic diversity in Bachman's Sparrows to determine whether natural barriers have led to distinct population units and to assess the effect of anthropogenic habitat loss and fragmentation. Genetic diversity was examined across the geographic range by genotyping 226 individuals at 18 microsatellite loci and sequencing 48 individuals at mitochondrial and nuclear genes. Multiple analyses consistently demonstrated little genetic structure and high levels of genetic variation, suggesting that populations are panmictic. Based on these genetic data, separate management units/subspecies designations or translocations to promote gene flow among fragmented populations do not appear to be necessary. Panmixia in Bachman's Sparrow may be a consequence of an historical range expansion and retraction. Alternatively, high vagility in Bachman's Sparrow may be an adaptation to the ephemeral, fire-mediated habitat that this species prefers. In recent times, high vagility also appears to have offset inbreeding and loss of genetic diversity in highly fragmented habitat.
Highlights
Genetic structure in wildlife populations is typically assessed with respect to natural barriers or anthropogenic habitat loss and fragmentation
We examined genetic structure and diversity in Bachman’s Sparrow to assess the potential effects of large natural barriers, such as the Mississippi River, and recent habitat loss and fragmentation
Most of our analyses showed high genetic diversity (Table 2), little to no inbreeding (Table 2), and weak genetic population structure (Tables 4, 5 & 6, Figures 3 & 6) for both microsatellite and sequence data
Summary
Genetic structure in wildlife populations is typically assessed with respect to natural barriers or anthropogenic habitat loss and fragmentation. Fragmented habitats created by natural barriers, such as rivers, oceans, deserts and mountain ranges, have documented major effects on population differentiation [1] and species-level diversity [2,3,4,5]. Population differentiation caused by natural barriers is important to identify because it may produce distinct lineages that warrant attention to ensure maintenance of biodiversity. In addition to natural habitat fragmentation, recent anthropogenic habitat fragmentation, degradation and loss have the potential to disrupt gene flow among populations [13]. Estimating genetic variation and inbreeding in habitat fragments is important because it can help to identify populations that may require management actions such as translocations to promote gene flow and protect evolutionary potential
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