Indirect connectivity estimates of amphibian breeding wetlands from spatially explicit occupancy models

Abstract

In conservation science, metapopulation models are frequently used to explore the spatial dynamics of organisms, and ultimately guide management decisions for threatened and endangered species. Pond‐breeding amphibians are often touted as a classic example of metapopulation structure. However, empirical assessment of this assumption is lacking for many species owing to the prohibitively high costs of movement studies. Our aim was to use spatially explicit occupancy models to evaluate metapopulation dynamics in an endangered amphibian. First, dynamic, spatially explicit occupancy‐based metapopulation models were fitted to 8 years of presence–absence data for the endangered reticulated flatwoods salamander, Ambystoma bishopi. Models were constructed to evaluate the spatial distribution of salamanders across the landscape, rate of patch turnover, and connectivity between patches. Second, the same data were analysed adopting an eigenvector mapping approach and spatial correlograms to investigate habitat characteristics associated with occupancy state. The second approach also yields an independent measure of patch connectivity to corroborate findings from the dynamic model. Both models predicted a steep drop‐off in connectivity with increasing isolation, and no evidence was found of interactions between wetlands separated by distances greater than 1.5 km. The best predictor of salamander occupancy status was the amount of understorey vegetation in wetland basins. Taken together, the two modelling approaches provide complementary information regarding the key determinants of occupancy in the focal species. Furthermore, several results directly translate to management recommendations. Connectivity between distant sites is low, and thus management units should be demarcated accordingly. Understorey vegetation represents egg‐laying habitat and refugia for larvae, and hence should be targeted in future restoration efforts. The methodologies employed in this paper have broad applicability to studies of pond‐breeding amphibians, particularly in situations where direct measures of dispersal are unobtainable.

Population structure, gene flow, and sex‐biased dispersal in the reticulated flatwoods salamander (Ambystoma bishopi): Implications for translocations

“…Accordingly, selecting suitable egg laying habitat is more difficult because females must anticipate inundation as compared to the spring where water is present when breeding begins. Consequently, for females, there is a strong selective pressure to choose breeding sites based on cues such as previous experience or pond‐associated vegetation (Brooks, Smith, Frimpong, et al, 2019). This pressure to select breeding sites may contribute to greater philopatry in fall breeding salamanders thus decreasing gene flow and increasing genetic structure (Burkhart et al, 2016, Peterman et al, 2015).…”

Responses of anuran diversity to wetland characteristics and surrounding landscape in the Southern Andean Yungas, Argentina

“…In conservation and restoration ecology, these integrated models are able to identify the most influential characteristics perceived by amphibians at different scales, thus helping to establish specific objectives to prioritize more effective conservation actions both in wetlands and surrounding landscapes to support local diversity of anurans. Brooks et al (2019) also argue that for amphibian conservation to be effective, the approach used should consider the breeding pond up to the scale of the surrounding landscape. By using an approach of combined spatial scales, decision‐makers can more effectively prioritize the habitat restoration of areas that facilitate species movements between potentially optimal sites for reproduction.…”

Peer Review #1 of "Using historical dip net data to infer absence of flatwoods salamanders in stochastic environments (v0.1)"

“…To account for imperfect detection, at least three surveys were conducted annually, spaced one per calendar month. Surveys were conducted during the months of January until May, and survey effort was standardized to 30 min for each occasion (see Brooks et al, 2019 for full description of field methods).…”

“…Statistical approach.-Using posterior distributions of year-specific detection probabilities derived from a recent occupancy study (Brooks et al, 2019), we investigated the impact of environmental stochasticity on long-term monitoring of Reticulated Flatwoods Salamanders.…”