Understanding metapopulation dynamics requires knowledge about local population dynamics and movement in both space and time. Most genetic metapopulation studies use one or two study species across the same landscape to infer population dynamics; however, using multiple co‐occurring species allows for testing of hypotheses related to different life history strategies. We used genetic data to study dispersal, as measured by gene flow, in three ambystomatid salamanders (Ambystoma annulatum, A. maculatum, and A. opacum) and the Central Newt (Notophthalmus viridescens louisianensis) on the same landscape in Missouri, USA. While all four salamander species are forest dependent organisms that require fishless ponds to reproduce, they differ in breeding phenology and spatial distribution on the landscape. We use these differences in life history and distribution to address the following questions: (1) Are there species‐level differences in the observed patterns of genetic diversity and genetic structure? and (2) Is dispersal influenced by landscape resistance? We detected two genetic clusters in A. annulatum and A. opacum on our landscape; both species breed in the fall and larvae overwinter in ponds. In contrast, no structure was evident in A. maculatum and N. v. louisianensis, species that breed during the spring. Tests for isolation by distance were significant for the three ambystomatids but not for N. v. louisianensis. Landscape resistance also contributed to genetic differentiation for all four species. Our results suggest species‐level differences in dispersal ability and breeding phenology are driving observed patterns of genetic differentiation. From an evolutionary standpoint, the observed differences in dispersal distances and genetic structure between fall breeding and spring breeding species may be a result of the trade‐off between larval period length and size at metamorphosis which in turn may influence the long‐term viability of the metapopulation. Thus, it is important to consider life history differences among closely related and ecologically similar species when making management decisions.

The success of species reintroductions can depend on a combination of environmental, demographic, and genetic factors. Although the importance of these factors in the success of reintroductions is well‐accepted, they are typically evaluated independently, which can miss important interactions. For species that persist in metapopulations, movement through and interaction with the landscape is predicted to be a vital component of persistence. Simulation‐based approaches are a promising technique for evaluating the independent and combined effects of these factors on the outcome of various reintroduction and associated management actions. We report results from a simulation study of bull trout (Salvelinus confluentus) reintroduction to three watersheds of the Pend Oreille River system in northeastern Washington State, USA. We used an individual‐based, spatially explicit simulation model to evaluate how reintroduction strategies, life history variation, and riverscape structure (e.g., network topology) interact to influence the demographic and genetic characteristics of reintroduced bull trout populations in three watersheds. Simulation scenarios included a range of initial genetic stocks (informed by empirical bull trout genetic data), variation in migratory tendency and life history, and two landscape connectivity alternatives representing a connected network (isolation‐by‐distance) and a fragmented network (isolation‐by‐barrier, using the known existing barriers). A novel feature of these simulations was the ability to consider the interaction of both demographic and genetic (i.e., demogenetic) factors in riverscapes with implicit asymmetric movement probabilities across the barriers. We found that connectivity (presence or absence of barriers) had the largest effect on demographic and genetic outcomes over 200 yr, with a greater effect than both initial genetic diversity and life history variation. We also identified regions of the study system in which bull trout populations persisted across a wide range of demographic, life history, and environmental connectivity parameters. Finally, we found no evidence that initial neutral genetic diversity influenced genetic diversity and structure after 200 yr; instead, genetic drift due to stray rate and population isolation dominated and erased any initial differences in genetic diversity. Our results highlight the utility of spatially explicit demogenetic approaches in exploring and understanding population dynamics—and their implications for management strategies—in fresh waters.

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Conservation and management activities are always constrained by finite resources. Therefore, decisions such as which sites to protect, whether existing habitat should be restored or whether new habitat should be created, and where on the landscape management efforts should be focused present difficult challenges. An overarching goal of many conservation or management plans is the long‐term persistence of populations, which is often dependent on functional connectivity and the maintenance of metapopulation dynamics. Graph theory and network approaches are frequently used tools for modeling functional connections between populations and between habitats. Less often, graph models are used to guide conservation or management decisions. We used spatial networks derived for an amphibian population to determine optimal locations to create new habitat, prioritize existing habitat for restoration, and determine the habitat most critical for maintaining connectivity within the existing metapopulation within Fort Leonard Wood, Missouri, USA, 2012–2014. Using data collected at 206 breeding ponds over 3 years, we constructed demographic networks representing the functional connectivity between ponds by dispersing ringed salamanders (Ambystoma annulatum). We incorporated uncertainty in key model parameters through Monte Carlo simulation, and used a graph‐theoretical parameterization of the metapopulation mean lifetime model to assess how changes in network structure affect persistence of the network. We conducted addition and removal experiments within our Monte Carlo simulations to rank and prioritize locations for pond creation, ponds for restoration, and ponds for preservation. Salamanders bred in 106 ponds in ≥1 year; 2.4% of ponds functioned predominantly as sources and 51% of occupied ponds functioned predominantly as sinks. The importance of a pond to the network was correlated with the number of emigrants dispersing from a pond, the number of ponds reached by these dispersers, and the frequency a pond functioned as a source. Creating new ponds at optimal locations increased the persistence of the network an average of 15.4% compared to randomly selected locations, whereas selective restoration of currently unoccupied ponds resulted in an average increase of 31.4% in network persistence, as compared to randomly selected unoccupied ponds. Through Monte Carlo simulation, we constructed biologically informed demographic connectivity networks for use as a spatial conservation or management planning tool. Although our approach was implemented with an amphibian and a breeding pond network, it is generalizable to any species occupying discrete habitat patches. © 2017 The Wildlife Society.

Body size differences among consumers often lead to asymmetric interactions, with larger individuals typically being stronger competitors and/or predators on small individuals. These types of interaction are particularly exemplified in freshwater pond communities, where substantial size variation exists both within and among species of top consumers. We investigated whether density dependence can modify the outcome of size‐structured interactions between larval stages of two pond‐breeding salamanders, Ambystoma annulatum and Ambystoma opacum. Size structure exists in populations of these species due to variation in the timing of breeding, which we hypothesised would amplify predation rates and competitive asymmetries from the early‐arriving species (A. annulatum) on the later‐arriving species (A. opacum). We manipulated the relative densities of both A. annulatum and A. opacum in outdoor mesocosms. We maintained the experiment through metamorphosis, and analysed size at metamorphosis, larval period length and survival of each species. Ambystoma annulatum imparted a strong density‐dependent effect on A. opacum through a combination of predation and competition. Survival of A. opacum was negatively related to the density of A. annulatum. For the A. opacum that survived, body size was reduced and larval period lengthened at higher A. annulatum densities, indicative of interspecific competition that was partly explained by resource pre‐emption. In contrast, A. annulatum was only affected by intraspecific density‐dependent competition. Our results suggest that density‐dependent effects reinforce asymmetric interactions among larval salamanders. However, the intensity of the asymmetric interactions is mediated by the arrival time and size of conspecifics. Specifically, earlier‐arriving species can negatively affect the later‐arriving species via size‐mediated predation and competition. The interactive effects of density dependence and arrival time of community members are probably a common mechanism generating size variability in ecological communities. Yet, most studies only evaluate one mechanism or the other. By interweaving these two processes, our work displays the importance of understanding context‐dependence in species interactions.

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Aim For many endemic species with limited dispersal capacities, the relationship between landscape changes and species distributions is still unclear. We characterized the population structure of the endemic ringed salamander (Ambystoma annulatum) across its distribution in the Central Interior Highlands (CIH) of North America, an area of high species endemism, to infer the ecological and evolutionary history of the species. Methods We sampled 498 individuals across the species distribution and characterized the population genetic structure using nuclear microsatellite and mitochondrial DNA (mtDNA) markers. Results Ambystoma annulatum exist in two strongly supported nuclear genetic clusters across the CIH that correspond to a northern cluster that includes the Missouri Ozark populations and a southern cluster that includes the Arkansas and Oklahoma Ozarks and the Ouachita Mountains. Our demographic models estimated that these populations diverged approximately 2,700 years ago. Pairwise estimates of genetic differentiation at microsatellite and mtDNA markers indicated limited contemporary gene flow and suggest that genetic differentiation was primarily influenced by changes in the post‐Pleistocene landscape of the CIH. Main Conclusions Both the geologic history and post‐European settlement history of the CIH have influenced the population genetic structure of A. annulatum. The low mtDNA diversity suggests a retraction into and expansion out of refugial areas in the south‐central Ozarks, during temperature fluctuations of the Pleistocene and Holocene epochs. Similarly, the estimated divergence time for the two nuclear clusters corresponds to changes in the post‐Pleistocene landscape. More recently, decreased A. annulatum gene flow may be a result of increased habitat fragmentation and alteration post‐European settlement.

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