Integrating dispersal, breeding and abundance data with graph theory for the characterization and management of functional connectivity in amphibian pondscapes

Abstract

Context Robust assessment of functional connectivity in amphibian population networks is essential to address their global decline. The potential of graph theory to characterize connectivity among amphibian populations has already been confirmed, but the movement data on which modelled graphs rely are often scarce and inaccurate. While probabilistic methods that account for intraspecific variability in dispersal better reflect the biological reality of functional connectivity, they must be informed by systematically recorded individual movement data, which are difficult to obtain for secretive taxa like amphibians. Objectives Our aim is to assess the applied potential of probabilistic graph theory to characterize overall connectivity across amphibian pondscapes using fine-scale capture-recapture data, and to inform conservation management based on the role of ponds on functional connectivity. Methods We monitored an amphibian community in a pondscape located in a Spanish “dehesa” for 2 years. Photoidentification was used to build capture histories for individuals of six species, from which dispersal kernels and population sizes were estimated to model probabilistic graphs. Results We obtained kernels of variable robustness for six species. Node importance for connectivity varied between species, but with common patterns such as shared road crossing areas and the presence of coincident interconnected pond clusters. Conclusions The combination of photoidentification, capture-recapture data and graph theory allowed us to characterize functional connectivity across the pondscape of study accounting for dispersal variability and identify areas where conservation actions could be most efficient. Our results highlight the need to account for interspecific differences in the study and management of amphibian pondscapes.

Assessing fine‐scale pondscape connectivity with amphibian eyes: An integrative approach using genomic and capture–mark–recapture data

“…Autocorrelation plots for five amphibian species using Euclidean distances as distances classes (in meters). Note the positive values of r in the smaller distance classes and differences in the vertical axis among species.east-west division shown by these graphs supported the overall role of the M601 road as a barrier for the local community of amphibians, which is concordant with the lack of detected cases of dispersal across the road in our five target species(Reyes-Moya et al, 2022). Some species presented isolated populations within one of the two sectors (e.g.…”

“…The road runs North–South, is 7 m wide and 20 km long, with a daily average intensity of 15,735 vehicles (Ayuntamiento de Collado Mediano, 2018). It divides the study area into western (with 33 ponds) and eastern (31 ponds) sectors, which were comprehensively monitored, as part of a previous study (Reyes‐Moya et al., 2022), during the flooding hydroperiods of the ponds in 2019 and 2020. In total, 64 ponds were sampled, 63 of them temporary (drying completely every year) and a permanent one.…”

“…For this study, we focused on the five most abundant species from the local amphibian community (Reyes‐Moya et al., 2022), three urodeles: Pleurodeles waltl Michahelles 1930, Triturus pygmaeus (Wolterstorff 1905) and Lissotriton boscai (Lataste 1879), and two anurans: Epidalea calamita (Laurenti 1768) and Pelophylax perezi (López‐Seoane 1885). All studied species differ in their biology, demography and movement ecology; information in this regard is summarized in Table 1.…”

“…The combination of both approaches in integrative studies has been rarely conducted (Cayuela, Besnard, et al., 2020; Murphy et al., 2015; Savary, Foltête, Moal, & Garnier, 2022), but has great potential to illuminate the relationships between genetic connectivity and demographic parameters. In this line, capture–mark–recapture (CMR) data allow comprehensive characterization of movement patterns by inferring connectivity graphs built from dispersal kernels based on movement records, demographic and geographical information (Reyes‐Moya et al., 2022); these graphs can, in turn, be contrasted with graphs based on genomic information by comparing inferred clusters, connections and node attributes (Savary, Foltête, Moal, & Garnier, 2022). These two methods provide complementary information: While CMR data provide information on movement patterns, these movements do not necessarily result in successful reproduction.…”

“…In this study, we conduct such an integrative approach to characterize fine‐scale patterns of connectivity in five syntopic amphibians differing in life‐history traits that breed in a system of 64 ponds in central Spain. We combine demographic and dispersal information from a 2‐year CMR study (Reyes‐Moya et al., 2022) with a genomic data set obtained from DNA samples of a subset of >1000 marked individuals. The combination of direct records of dispersal distances and frequencies, estimates of relative abundance and genome‐wide data (thousands of SNPs) in five species with different life‐history traits allowed comparative inference of patterns of population structure at a spatial scale adjusted to the most common displacement distances in the study species.…”