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

K. C. Burns,Daniel Escoriza

doi:10.1111/ddi.13206

Abstract

AbstractAimTo identify and evaluate the environmental properties of the Mediterranean islands that make them a suitable habitat for their endemic lizards. This would represent an important improvement in our knowledge and would assist the conservation of these lizards, which are threatened by both the expansion of mainland species and the increasing intensity of human disturbance on these islands.LocationMediterranean Basin.MethodsI assessed the environmental associations of 50 species of lizard (19 endemic) across 552 Mediterranean islands using outlying mean index analysis. The strength of the species responses was assessed using binomial generalized linear models.ResultsThe presence of endemic species is positively correlated with the distance of the island from the mainland. Island connectivity is also positively correlated with an increased presence of endemic lizards, but not with an increased presence of mainland species (i.e. those with exclusive or mainly continental natural distribution). In addition, island size, temperature and vegetation productivity are positively correlated with the presence of mainland species. Outlying mean index (OMI) analysis showed that the endemic species occupy niche positions that are similar to the average environmental conditions in the archipelago, but frequently without using the entire range of niches. The mainland species usually occur in more peripheral positions in the environmental space, except for some highly expansive species.ConclusionsLizards that are endemic to the Mediterranean islands were found to be present on a large number of islands within an archipelago, but they quickly disappear as the conditions change, largely because of human activity. Large islands act as population reservoirs for mainland species, facilitating secondary colonization of peripheral islets.

Highlights

| INTRODUCTIONESCORIZA and BURNS as populations are smaller (Schoener & Schoener, 1983). Extinctions are common on larger islands, but in some situations, endemic populations may remain depending on their interactions with the introduced mainland species or the existence of refuge habitats (Fox & Fox, 2000; Olson et al, 2006)
Islands are seen as a paradigm for vulnerable ecosystems because of the rapid loss of diversity that usually occurs after human arrival (Loehle & Eschenbach, 2012)
The arrival of humans was synchronous with significant changes in the fauna and botanical composition across the Mediterranean islands, which suggests that human activity led to significant environmental impacts (Gippoliti & Amori, 2006; Jalut et al, 2009)

Summary

| INTRODUCTION

ESCORIZA and BURNS as populations are smaller (Schoener & Schoener, 1983). Extinctions are common on larger islands, but in some situations, endemic populations may remain depending on their interactions with the introduced mainland species or the existence of refuge habitats (Fox & Fox, 2000; Olson et al, 2006). The Mediterranean Basin provides an interesting setting that can be used to evaluate patterns of coexistence among mainland and endemic island faunas. Despite the long history of disturbance, reptile extinctions in the Mediterranean islands have been scarce, at least when compared with other groups of vertebrates (Bover et al, 2008). These extinctions affected large species, such as giant tortoises, turtles and lizards on Malta, and isolated populations of extant species, such as Testudo marginata on Crete and Podarcis lilfordi on Mallorca and Menorca (Bachmayer et al, 1976; Böhme & Zammit-Maempel, 1982; Terrasa et al, 2009). I hypothesized that isolation relative to other islands in an archipelago would be negatively associated with both groups of lizards

| MATERIALS AND METHODS

Findings

| DISCUSSION

| CONCLUSIONS