Ecological connectivity assessment in a strongly structured fire salamander (Salamandra salamandra) population

Abstract

Small populations are more prone to extinction if the dispersal among them is not adequately maintained by ecological connections. The degree of isolation between populations could be evaluated measuring their genetic distance, which depends on the respective geographic (isolation by distance, IBD) and/or ecological (isolation by resistance, IBR) distances. The aim of this study was to assess the ecological connectivity of fire salamander Salamandra salamandra populations by means of a landscape genetic approach. The species lives in broad-leaved forest ecosystems and is particularly affected by fragmentation due to its habitat selectivity and low dispersal capability. We analyzed 477 biological samples collected in 47 sampling locations (SLs) in the mainly continuous populations of the Prealpine and Eastern foothill lowland (PEF) and 10 SLs in the fragmented populations of the Western foothill (WF) lowland of Lombardy (northern Italy). Pairwise genetic distances (Chord distance, DC) were estimated from allele frequencies of 16 microsatellites loci. Ecological distances were calculated using one of the most promising methodology in landscape genetics studies, the circuit theory, applied to habitat suitability maps. We realized two habitat suitability models: one without barriers (EcoD) and a second one accounting for the possible barrier effect of main roads (EcoDb). Mantel tests between distance matrices highlighted how the Log-DC in PEF populations was related to log-transformed geographic distance (confirming a prevalence of IBD), while it was explained by the Log-EcoD, and particularly by the Log-EcoDb, in WF populations, even when accounting for the confounding effect of geographic distance (highlighting a prevalence of IBR). Moreover, we also demonstrated how considering the overall population, the effect of Euclidean or ecological distances on genetic distances acting at the level of a single group (PEF or WF populations) could not be detected, when population are strongly structured.

Increased genetic structuring of isolatedSalamandra salamandrapopulations (Caudata: Salamandridae) at the margins of the Carpathian Mountains

“…; Bani et al. ; Straub et al. ), this small Budapest population which is estimated to consist of a few thousand individuals (Kiss I and Vörös J. et al.…”

“…This isolated population has been rediscovered in 2008 in the outskirts of Budapest, where the species was last reported in 1918. Although S. salamandra is considered to be a good disperser (Schmidt et al 2007;Schulte et al 2007) and sometimes even highways have no effect on population differentiation Bani et al 2015;Straub et al 2015), this small Budapest population which is estimated to consist of a few thousand individuals (Kiss I and V€ or€ os J. et al unpublished), is entirely surrounded by the settlement. Considering the lack of suitable habitats, gene flow with the closest population (Visegr ad Mountains) within 21 km seems implausible.…”

Effects of landscape features on gene flow among urban frog populations

“…In conclusion, our methods were effective in identifying factors affecting habitat isolation. The latter phenomenon exerts a strong effect on population persistence, disrupting adaptive and evolutionary processes (Templeton, Robertson, Brisson, & Strasburg, ) in fragmented landscapes (Bani et al, ; Igawa et al, ; Reed et al, ; but see Keeley, Beier, Keeley, & Fagan, ).…”

Behavior in a Changing Landscape: Using Movement Ecology to Inform the Conservation of Pond-Breeding Amphibians

“…Ambystoma maculatum Forest Males: 100 m Females: 200 m 2,000-4,000 m Zamudio and Wieczorek, 2007;Purrenhage et al, 2009 Ambystoma opacum Forest 200-400 m 1,300 m Gamble et al, 2007 Salamandra salamandra Forest 50-300 m 1,000-4,000 m Schulte et al, 2007;Bani et al, 2015 Bufo bufo Forest 550 m 1,000-3,600 m Moore, 1954;Daversa et al, 2012 Anaxyrus hemiophrys Forest 50-100 m 10,000 m Constible et al, 2010;Muths et al, 2018 Epidalaea calamita Open environment 700 m 3,000-12,000 m Miaud et al, 2000;Sinsch et al, 2012;Frei et al, 2016 Rana luteiventris Mixed Males: 200 m Females: 1,030 m 5,750 m Pilliod et al, 2002;Funk et al, 2005 in the others. However, the overall evolutionary challenge is to predict the propensity of leaving the natal population.…”