Seasonal variation in microhabitat of salamanders: environmental variation or shift of habitat selection?

Abstract

Relationships between species and their habitats are not always constant. Different processes may determine changes in species-habitat association: individuals may prefer different habitat typologies in different periods, or they may be forced to occupy a different habitat in order to follow the changing environment. The aim of our study was to assess whether cave salamanders change their habitat association pattern through the year, and to test whether such changes are determined by environmental changes or by changes in preferences. We monitored multiple caves in Central Italy through one year, and monthly measured biotic and abiotic features of microhabitat and recorded Italian cave salamanders distribution. We used mixed models and niche similarity tests to assess whether species-habitat relationships remain constant through the year. Microhabitat showed strong seasonal variation, with the highest variability in the superficial sectors. Salamanders were associated to relatively cold and humid sectors in summer, but not during winter. Such apparent shift in habitat preferences mostly occurred because the environmental gradient changed through the year, while individuals generally selected similar conditions. Nevertheless, juveniles were more tolerant to dry sectors during late winter, when food demand was highest. This suggests that tolerance for suboptimal abiotic conditions may change through time, depending on the required resources. Differences in habitat use are jointly determined by environmental variation through time, and by changes in the preferred habitat. The trade-offs between tolerance and resources requirement are major determinant of such variation.

Cases of albinism and leucism in amphibians in Italy: new reports

“…Within our observations, 16 individuals belong to the genus Hydromantes: these animals are characterized by direct development so they lack a larval stage (Lanza et al, 2006). Moreover, Hydromantes species often exploit underground environments to avoid unsuitable epigean environmental conditions (Lunghi et al, 2015). Thus, the short time in which these animals are most vulnerable (juvenile stage) and the subterranean habitat in which there are few predators, may reduce cave salamander mortality.…”

“…We performed extensive surveys, mainly during spring and autumn seasons for numerous breeding sites and their surrounding areas in northern Italy and Sardinia, in order to observe both the adult and larval stages for each amphibian species. Moreover, we performed extensive samplings all year round on the Italian cave salamanders [genus Hydromantes; see Wake (2013) in caves and artificial tunnels (more than 5000 individuals observed)], as these species lack an aquatic larval stage (Lanza et al, 2006) and in underground environments their detectability is high (Lunghi et al, 2015). All encountered depigmented individuals were photographed and measured.…”

Transgressive niche across a salamander hybrid zone revealed by microhabitat analyses

“…We surveyed 121 natural and artificial caves along the hybrid contact zone and across the whole range of the two parental species ( H. ambrosii and H. italicus ; Figure a). Surveys were performed in early summer (June–July 2012–2016), when conditions outside the caves are unfavourable and the detection of salamanders active underground is highest (Lunghi et al, ). We performed all the surveys during the central hours of dry and sunny days.…”

“…With our sampling protocol, detection probability is high but lower than one (approx. 0.75 per visit) (Ficetola et al, ; Lunghi et al, ). Therefore, in our models absences received a weight of 0.75 (following Gomez‐Rodriguez, Bustamante, Diaz‐Paniagua, & Guisan, ).…”

Cave exploitation by an usual epigean species: a review on the current knowledge on fire salamander breeding in cave

“…However, most of studies on underground animals focus on obligate cave dwellers, while only few consider underground populations of usually epigeous species (Lunghi et al 2015;Lunghi et al 2017).…”