How landscape and biotic interactions shape a Mediterranean reptile community

Abstract

Context Disentangling the effect of environment and biological interaction on community composition with observational data, within the environmental filtering framework, is challenging because the two processes produce non independent results. Objectives Adopting community N-mixture models with symmetric interactions, we aimed at estimating differential effects of landscape structure and biotic interactions on the local abundance of a Mediterranean reptile community including four lizards (Lacerta bilineata; Podarcis siculus; P. muralis; Chalcides chalcides) and two snakes (Hierophis viridiflavus; Natrix Helvetica). Methods We sampled reptiles for three consecutive years (2019–2021; 4 surveys/year) on 52 linear transects on a Mediterranean coastal landscape. We analyzed count data by means of a multi-species N-mixture model with symmetric interactions. Interactions within pair of species were estimated from the residual correlation of their realized abundances, after accounting for four landscape features: landscape heterogeneity calculated from land cover data, edge density of woody vegetation patches, tree cover density, net primary productivity. Results Most species displayed very low detection probability (p ~ 0.10). All species responded with different intensity and sensitivity to landscape predictors. Two biological interactions resulted significant: L. bilineata and P. siculus showed a positive interaction, while P. muralis and C. chalcides displayed a negative interaction. Conclusions Using community N-mixture models we demonstrated that, also with observational data obtained from a realized community, partitioning the filtering process of the landscape from the one of biotic interactions is possible.

Disentangling Exploitative and Interference Competition on Forest Dwelling Salamanders

“…We counted salamanders in all plots during three repeated surveys over a short time period. We then used count data to model abundance and activity interaction occurring between the species, using a two-species N-mixture model [ 31 ], while incorporating environmental covariates [ 33 , 34 , 35 , 36 , 37 , 38 ].…”

“…During each survey the observer searched for salamanders within each plot for four minutes [ 37 , 43 ], checking the leaf litter, inspecting rock crevices with a flashlight, and lifting temporary shelters such as superficial rocks and dead wood in search of salamanders. Since both species are known to be active during or immediately after rain and considering that inactive individuals retreat underground and are usually unavailable for sampling, we considered both individuals encountered on the forest floor and those found under temporary shelters as active on the surface [ 37 , 38 , 41 ]. We assigned each individual to one of the two study species and their abundance in each plot recorded.…”

“…Likewise, to model the possible presence of interference competition resulting from reduced activity of the smaller species when the larger one is active, we considered the detection probability p of both species to be a rough proxy of species’ surface activity. This approach is widely shared and often successfully used in ecological studies assessing species interactions [ 37 , 38 , 46 ]. Therefore, we added another interaction term ( ε ) on the detection process, using the detection probability pij of S. strinatii as a covariate on the detection of S. perpicillata .…”

Environment drives color pattern polymorphism in sand lizards beyond the Gloger's rule

“…Coloration will better match background and provide camouflage if predation is stronger than sexual selection, whereas sexual selection will favor increased intraspecific visual signaling (Bruinjé et al., 2019). Biotic and abiotic factors influence coloration evolution and persistence of color variants in populations (McLean et al., 2015; Romano et al., 2022). Identifying the relationships between morph composition and climate with more complex scenarios where sexual selection interacts with other types of selection are of particular interest (Clusella‐Trullas et al., 2010; McLean et al., 2015).…”