Landscape genetics of northern crested newt Triturus cristatus populations in a contrasting natural and human-impacted boreal forest

Abstract

Among vertebrates, amphibians currently have the highest proportion of threatened species worldwide, mainly through loss of habitat, leading to increased population isolation. Smaller amphibian populations may lose more genetic diversity, and become more dependent on immigration for survival. Investigations of landscape factors and patterns mediating migration and population genetic differentiation are fundamental for knowledge-based conservation. The pond-breeding northern crested newt (Triturus cristatus) populations are decreasing throughout Europe, and are a conservation concern. Using microsatellites, we studied the genetic structure of the northern crested newt in a boreal forest ecosystem containing two contrasting landscapes, one subject to recent change and habitat loss by clear-cutting and roadbuilding, and one with little anthropogenic disturbance. Newts from 12 breeding ponds were analyzed for 13 microsatellites and 7 landscape and spatial variables. With a Maximum-likelihood population-effects model we investigated important landscape factors potentially explaining genetic patterns. Results indicate that intervening landscape factors between breeding ponds, explain the genetic differentiation in addition to an isolation-by-distance effect. Geographic distance, gravel roads, and south/south-west facing slopes reduced landscape permeability and increased genetic differentiation for these newts. The effect was opposite for streams, presumably being more favorable for newt dispersal. Populations within or bordering on old growth forest had a higher allelic richness than populations in managed forest outside these areas. Old growth forest areas may be important source habitats in the conservation of northern crested newt populations.

Context‐dependent dispersal determines relatedness and genetic structure in a patchy amphibian population

“…Overall, these results indicate that clusters and subclusters behave like independent demographic/genetic units with limited gene flow between them. They are therefore consistent with previous studies that have highlighted strong genetic differentiation in T. cristatus at similar spatial scales (Haugen et al, 2020;Schön et al, 2011). In our study system, limited gene flow between demographic/genetic units separated from each other by relatively short Euclidean distances (from 3 to 27 km) is probably caused by the short distances that T. cristatus seem to move; dispersal kernels quantified at the SSP level showed that movements exceeding 1 km are rare events.…”

“…They are therefore consistent with previous studies that have highlighted strong genetic differentiation in T . cristatus at similar spatial scales (Haugen et al, 2020; Schön et al, 2011). In our study system, limited gene flow between demographic/genetic units separated from each other by relatively short Euclidean distances (from 3 to 27 km) is probably caused by the short distances that T .…”

“…cristatus seem to move; dispersal kernels quantified at the SSP level showed that movements exceeding 1 km are rare events. Furthermore, physical barriers could also limit the movement of newts in the landscape matrix (Haugen et al, 2020), increasing genetic differentiation among clusters and subclusters.…”

“…In our study system, limited gene flow between demographic/genetic units separated from each other by relatively short Euclidean distances (from 3 to 27 km) is probably caused by the short distances that T. cristatus seem to move; dispersal kernels quantified at the SSP level showed that movements exceeding 1 km are rare events. Furthermore, physical barriers could also limit the movement of newts in the landscape matrix (Haugen et al, 2020), increasing genetic differentiation among clusters and subclusters.…”

Population structure and genetic diversity of the threatened pygmy newt Triturus pygmaeus in a network of natural and artificial ponds

“…Thus, the inferred connectivity suggests that pygmy newts do not face significant barriers to dispersal in this region. In this vein, although some other studies of amphibian populations have reported a pattern of isolation by distance and a high degree of genetic structuring (e.g., Kraaijeveld-Smit et al 2005;Sarasola-Puente et al 2012;Albert et al 2015;Mims et al 2016;Haugen et al 2020), it is nowadays commonly assumed that when pond networks are separated by these approximate distances ( ∼ 10 km), anurans and salamanders are capable to disperse at a rate that make even isolated populations connected to the whole (Smith and Green 2005;Denoël et al 2018;Cayuela et al 2020b;Yannic et al 2021).…”