Organization of Squamata (Reptilia) assemblages in Mediterranean archipelagos

Abstract

Mediterranean islands have complex reptile assemblages, but little is known about the factors that determine their organization. In this study, the structure of assemblages of Squamata was evaluated based on their species richness and two measures of phylogenetic diversity (variability and clustering). I evaluated the composition of the assemblages comparing distinct biogeographic subregions within the Mediterranean: Adriatic, Aegean, Balearic, Corsica–Sardinia, Crete, Gulf of Gabés, Ionian Sea, Ligurian Sea, Malta, Sicily, and Tyrrhenian Sea. The effect of island environments and geographical isolation on the diversity metrics was assessed using generalized linear models. The analyses indicated that species richness was mostly influenced by island area and geographical isolation. Assemblages on smaller islands were poorer in species and phylogenetically dispersed, possibly as an effect of interspecific competition. The species composition of the assemblages was determined by similar environmental drivers within the biogeographic subregions, including island area, island elevation, geographical isolation, and aridity. In several subregions, significant patterns of phylogenetic attraction were found in species co‐occurrences, caused by the limits imposed by the island size on large predatory species.

Dispersal patterns of Squamata in the Mediterranean: An evolutionary perspective

“…This finding indicated that no squamate lineages in the Mediterranean basin had greater dispersal capacities than others. It was also feasible that more intense interspecific competition between phylogenetic relatives in small islands (Escoriza, 2020) could counteract the effects of traits that might possibly enhance transmarine dispersal.…”

What makes an island a suitable refuge for an endemic lizard?

“…In the case of at least one species, P. siculus , expansion has been correlated with the rapid decline of island endemic species, but adverse effects have also been postulated for the other species (D'Amico et al., 2018; Mayol‐Serra, 1977). Although islets are colonized by species of alien reptiles that are quite diverse phylogenetically (Escoriza, 2020b), those evolutionarily close to endemics, as using similar resources, are frequently associated with the collapse of native populations (Nikolic et al., 2019).…”

“…Although islets are colonized by species of alien reptiles that are quite diverse phylogenetically (Escoriza, 2020b), those evolutionarily close to endemics, as using similar resources, are frequently associated with the collapse of native populations (Nikolic et al, 2019).…”