The role of Podarcis siculus in island reptile communities

The project

Biotic interactions among species play a key role in shaping the structure and dynamics of ecological communities. In this context, alien species can alter natural balances and negatively affect native species, especially in small and isolated environments such as islands.

The Italian wall lizard (Podarcis siculus) is one of the reptile species most frequently introduced outside its native range, and negative, sometimes substantial, effects on local reptile communities have been documented. However, the ecological mechanisms underlying these interactions and their long-term consequences for native species are not yet fully understood.

Aim

The main aim of this PhD project is to assess the effects of Podarcis siculus on reptiles inhabiting Mediterranean islands, analysing the role of biotic interactions and competition at different spatial scales.

Specifically, the project aims to:

• assess the role of biotic interactions in shaping the distribution and co-occurrence patterns of reptile species on Mediterranean islands;
• analyse coexistence processes and spatial competition between P. siculus and native species at the local scale;
• evaluate the potential effects of P. siculus presence on population abundance, microhabitat use, body condition and thermoregulation capacity of native species.

Methods

The project combines macroecological analyses and fieldwork through:

• co-occurrence analyses and community distribution models to identify and describe species associations and assess the relative contribution of environmental factors and biotic interactions to species distributions at the Mediterranean scale;
• multi-species occupancy models to analyse species occurrence probability and the environmental and biotic factors influencing distribution at the local scale;
• demographic estimation models, such as N-mixture models, to evaluate potential differences in population abundance in relation to the presence of P. siculus;
• collection of morphometric, environmental and thermal data to assess potential effects of competition on the ecological and physiological strategies of native species in sites occupied with or without P. siculus.

Collected data include snout-vent length, body mass, characteristics of selected and available microhabitats, body temperature, operative temperature and thermal niche traits.

Expected contribution

The results of the project will contribute to a better understanding of ecological dynamics in island communities and provide useful information for the conservation of Mediterranean reptiles threatened by biological invasions.

Gallery

Images from the project

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Photo: Mariomassone / Wikimedia Commons , licensed under CC BY-SA 4.0 .