Fine‐scale spatial genetic structure and dispersal among spotted salamander (Ambystoma maculatum) breeding populations

Abstract

We examined fine-scale genetic variation among breeding aggregations of the spotted salamander (Ambystoma maculatum) to quantify dispersal, interpopulation connectivity and population genetic structure. Spotted salamanders rely on temporary ponds or wetlands for aggregate breeding. Adequate breeding sites are relatively isolated from one another and field studies suggest considerable adult site fidelity; therefore, we expected to find population structure and differentiation at small spatial scales. We used microsatellites to estimate population structure and dispersal among 29 breeding aggregations in Tompkins County, New York, USA, an area encompassing 1272 km(2). Bayesian and frequency-based analyses revealed fine-scale genetic structure with two genetically defined demes: the North deme included seven breeding ponds, and the South deme included 13 ponds. Nine ponds showed evidence of admixture between these two genetic pools. Bayesian assignment tests for detection of interpopulation dispersal indicate that immigration among ponds is common within demes, and that certain populations serve as sources of immigrants to neighbouring ponds. Likewise, spatial genetic correlation analyses showed that populations < or = 4.8 km distant from each other show significant genetic correlation that is not evident at higher scales. Within-population levels of relatedness are consistently larger than expected if mating were completely random across ponds, and in the case of a few ponds, within-population processes such as inbreeding or reproductive skew contribute significantly to differentiation from neighbouring ponds. Our data underscore the importance of these within-population processes as a source of genetic diversity across the landscape, despite considerable population connectivity. Our data further suggest that spotted salamander breeding groups behave as metapopulations, with population clusters as functional units, but sufficient migration among demes to allow for potential rescue and recolonization. Amphibian habitats are becoming increasingly fragmented and a clear understanding of dispersal and patterns of population connectivity for taxa with different ecologies and life histories is crucial for their conservation.

Genetic drift and rapid evolution of viviparity in insular fire salamanders (Salamandra salamandra)

“…The F ST values obtained were higher than those documented in other fine-scale salamander studies (Cabe et al, 2007;Zamudio and Wieczorek, 2007;Purrenhage et al, 2009) and frog island populations (Lind et al, 2010), but showed similar levels of divergence to other amphibian population genetic studies covering larger regions (Spear et al, 2005;Savage et al, 2010). The similarities in genetic diversity and demographics among island and coastal populations (Table 1; Figure 3) underscore their similar histories, despite the current differences in connectivity to the mainland.…”

Applying new inter-individual approaches to assess fine-scale population genetic diversity in a neotropical frog, Eleutherodactylus ockendeni

“…With microsatellites, r-values of 0.015-0.06 in Rana temporaria (Johansson et al, 2005) and ca. 0.06 in spotted salamanders, Ambystoma maculatum (Zamudio and Wieczorek, 2007), were reported. Moran's-I of single minisatellite alleles in Bufo bufo in Great Britain ranged widely, from À0.03 to 0.07 (Scribner et al, 2001).…”

Effective population size is strongly correlated with breeding pond size in the endangered California tiger salamander, Ambystoma californiense

“…Pondbreeding amphibians provide especially good study systems for examining the effects of aquatic breeding habitats on population parameters, because breeding ponds have quantifiable features and often demarcate discrete yearly cohorts of breeding populations. Additionally, amphibians are facing local and global declines (Fisher and Shaffer 1996;Houlahan et al 2000;Collins and Storfer 2003;Stuart et al 2004) and are often sensitive to anthropogenic habitat alteration (Guerry and Hunter 2002;Zamudio and Wieczorek 2007). Thus, studies linking breeding habitat and population persistence may play a critical role in conservation and management strategies (Gibbs 1998;Guerry and Hunter 2002;Funk et al 2005;Rittenhouse and Semlitsch 2006).…”