Fine-scale functional connectivity of two syntopic pond-breeding amphibians with contrasting life-history traits: an integrative assessment of direct and indirect estimates of dispersal

Abstract

Assessing patterns of functional connectivity among amphibian demes is crucial to unravel their population dynamics and prevent their isolation and eventual extinction. Integrative studies based on direct (capture-mark-recapture) and indirect (genetic) estimates of dispersal provide robust, biologically realistic inferences on population structure and connectivity, with applications for conservation efforts. We focused on two pond-breeding amphibians with contrasting life-history traits: the short-lived, semi-arboreal Hyla molleri and the long-lived, fossorial Pelobates cultripes. We PIT-tagged 2150 individuals of both species in two ponds (Laguna and Gravera, separated by 700 m) and monitored them from 2009 to 2021 to document the frequency and spatial extent of dispersal events. In addition, we genotyped individuals from these and two additional breeding populations at a maximum distance of 5 km with 15–16 microsatellites to characterize fine-scale patterns of genetic structure. We detected dispersal events connecting Laguna and Gravera in both species, albeit at low frequencies (4.8% and 7.7% of recaptured individuals of H. molleri and P. cultripes, respectively). However, both species were capable of covering long distances, with individual accumulated displacements up to 3.5 km (Hyla) and 1.8 km (Pelobates). Breeding populations > 2 km apart were genetically differentiated, indicating lower connectivity at this spatial scale. Estimates of pairwise migration rates differed between species and were asymmetrical, with different ponds representing “source” populations contributing more migrants to other populations in each species. We discuss the role of differences in life history traits and ecological preferences in shaping population dynamics in the two species and highlight management implications of our results.