Environmental suitability models predict population density, performance and body condition for microendemic salamanders

Abstract

Species can show strong variation of local abundance across their ranges. Recent analyses suggested that variation in abundance can be related to environmental suitability, as the highest abundances are often observed in populations living in the most suitable areas. However, there is limited information on the mechanisms through which variation in environmental suitability determines abundance. We analysed populations of the microendemic salamander Hydromantes flavus, and tested several hypotheses on potential relationships linking environmental suitability to population parameters. For multiple populations across the whole species range, we assessed suitability using species distribution models, and measured density, activity level, food intake and body condition index. In high-suitability sites, the density of salamanders was up to 30-times higher than in the least suitable ones. Variation in activity levels and population performance can explain such variation of abundance. In high-suitability sites, salamanders were active close to the surface, and showed a low frequency of empty stomachs. Furthermore, when taking into account seasonal variation, body condition was better in the most suitable sites. Our results show that the strong relationship between environmental suitability and population abundance can be mediated by the variation of parameters strongly linked to individual performance and fitness.

What shapes the trophic niche of European plethodontid salamanders?

“…In such areas predator pressure for this salamanders is generally low, and almost no closely related taxa (i.e., urodela species) are exploiting the same environment, thus limiting the occurrence of intraspecific competition [ 76 , 77 ]. Our findings confirm that the feeding activity of individuals is higher in the areas close to the cave entrance [ 70 ], being thus in agreement with the habitat segregation hypothesis [ 72 ]…”

“…The frequency of empty stomachs, and the number of prey per salamander, was strongly related with the distance from the cave entrance. Salamanders with empty stomachs and those with few prey items were more frequently found in the deepest sectors of caves [ 70 ]. Previous studies on Hydromantes salamanders showed spatial segregation, with different age classes and sexes exploiting different cave sectors [ 71 , 72 ].…”

Occupancy patterns and upper range limits of lowland Bornean birds along an elevational gradient

“…Many species do, however, appear to be more abundant at sites predicted to be more suitable by species distribution models (Lunghi et al, 2018;Weber, Stevens, Diniz-Filho, & Grelle, 2017).…”

“…Gradients in many abiotic factors (e.g. temperature, rainfall) are gradual and correlated with elevation (Lomolino, 2001;Lunghi et al, 2018). This means that elevational distance should be a better proxy for environmental distance than is spatial distance over large geographical areas, making "rare periphery" patterns theoretically more likely when measured elevationally (Brown, 1984;Van Couwenberghe et al, 2013) (Doughty & Goulden, 2008).…”

“…Consequently, most studies have provided only partial tests of these hypotheses, limited by both the difficulties listed above and a lack of data from the edges of species distributions (Santini et al, ). Many species do, however, appear to be more abundant at sites predicted to be more suitable by species distribution models (Lunghi et al, ; Weber, Stevens, Diniz‐Filho, & Grelle, ).…”