Limited influence of local and landscape factors on finescale gene flow in two pond‐breeding amphibians

Abstract

Dispersal and gene flow within animal populations are influenced by the composition and configuration of the landscape. In this study, we evaluated hypotheses about the impact of natural and anthropogenic factors on genetic differentiation in two amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Lithobates sylvaticus) in a commercial forest in central Maine. We conducted this analysis at two scales: a local level, focused on factors measured at each breeding pond, and a landscape level, focused on factors measured between ponds. We investigated the effects of a number of environmental factors in six categories including Productivity, Physical, Land Composition, Land Configuration, Isolation and Location. Embryos were sampled from 56 spotted salamander breeding ponds and 39 wood frog breeding ponds. We used a hierarchical Bayesian approach in the program GESTE at each breeding pond and a random forest algorithm in conjunction with a network analysis between the ponds. We found overall high genetic connectivity across distances up to 17 km for both species and a limited effect of natural and anthropogenic factors on gene flow. We found the null models best explained patterns of genetic differentiation at a local level and found several factors at the landscape level that weakly influenced gene flow. This research indicates multiscale investigations that incorporate local and landscape factors are valuable for understanding patterns of gene flow. Our findings suggest that dispersal rates in this system are high enough to minimize genetic structuring and that current forestry practices do not significantly impede dispersal.

Locomotor endurance predicts differences in realized dispersal between sympatric sexual and unisexual salamanders

“…At spatial scales similar to those in this study, Ambystoma salamanders display high levels of gene flow between populations (Newman & Squire ; Zamudio & Wieczorek ; Purrenhage, Niewiarowski & Moore ; Coster et al . ). However, this connectivity is spatially dependent, with greater population differentiation at larger scales, as would be predicted by an isolation‐by‐distance model.…”

Comparative landscape genetics of pond‐breeding amphibians in Mediterranean temporal wetlands: The positive role of structural heterogeneity in promoting gene flow

“…Leaving aside the common effect of topography on both species, land cover‐related categorical variables did not have an important role in shaping genetic structure. Some studies have previously reported negative effects of roads on gene flow in anurans (Richardson, ) and salamanders (Coster et al., ). Nevertheless, models including road density as a variable were not well supported in either species (Table ).…”

“…Comparative landscape genetics studies on codistributed species have great potential to design cost‐effective conservation plans focusing on measures favouring a wider set of taxa, but are still relatively scarce. So far, comparative studies have focused primarily on vertebrates, including amphibians (Coster, Babbitt, Cooper, & Kovach, ; Richardson, ; Zancolli, Rödel, Steffan‐Dewenter, & Storfer, ), mammals (Dudaniec et al., ; Frantz et al., ; Muscarella, Murray, Ortt, Russell, & Fleming, ), and fishes (Olsen et al., ) and more occasionally on invertebrates (Engler, Balkenhol, Filz, Habel, & Rödder, ; Ortego, García‐Navas, Noguerales, & Cordero, ; Phillipsen et al., ). These multi‐species studies may allow identifying interspecific differences in the way landscape features influence connectivity and gene flow and provide general guidelines for land management programmes aimed at protecting biological communities or ecosystems (Goldberg & Waits, ; Keller, Holderegger, Strien, & Bolliger, ; Nicholson & Possingham, ; Schwenk & Donovan, ).…”

“…Due to their low dispersal abilities (Bowne & Bowers, ; Graeter, Rothermel, & Gibbons, ), small effective population sizes (Funk, Tallmon, & Allendorf, ) and the discontinuous distribution of their preferred breeding habitats (Jehle, Burke, & Arntzen, ), they tend to form “patchy” breeding assemblages. Dispersal and the maintenance of gene flow between breeding ponds depends on the composition and configuration of the landscape (Coster et al., ), and studies focusing on functional connectivity have described different species responses to landscape features such as differences in soil moisture, clear‐cut habitats, agriculture lands, riparian network, as well as differences in metamorphosis, philopatry, dispersal, selection of breeding sites and post‐breeding behaviour (Coster et al., ; Goldberg & Waits, ; Peterman et al., ; Richardson, ; Steele et al., ). Identification of the factors promoting or reducing gene flow is key to prevent local and regional extinctions in the long‐term and to inform conservation management.…”

Landscape genetics reveals unique and shared effects of urbanization for two sympatric pool‐breeding amphibians

“…Tracking studies suggest altered habitats between pools can reduce overall dispersal propensities (Cline & Hunter, , ). Despite these observed ecological effects, signals of urbanization‐related influences on the genetic structure of pool‐breeding amphibians have not been consistently detected (e.g., Coster, Babbitt, Cooper, & Kovach, ; Peterman et al, ; Richardson, ; Table ). In some of these cases, a lack of effect could be associated with the surveyed spatial extents that were relatively small and that may not be commensurate with the scales over which drift–migration equilibrium is most disrupted and detectable.…”