Patterns of alpha diversity among Tunisian lizards (Lacertidae)

Reptiles are a successful group in subtropical arid regions. However, little is known about the drivers that influence the diversity of arid reptile communities. One approach is to investigate the variation in phylogenetic structure of the communities along a broad environmental gradient. In this study, I investigated these patterns in the communities of lacertids at the periphery of the Sahara Desert in Tunisia. The effect of the environment was assessed based on a set of variables describing the climate, topography, substrate and cover of perennial vegetation. The phylogenetic alpha diversity was described using the mean pairwise distance (MPD) and the mean nearest taxon distance (NTD) metrics. The analyses showed that the lacertid species could be clustered into three main ecological groups: mesic (Podarcis vaucheri, Psammodromus algirus, Psammodromus blanci, Timon pater), xeric (Acanthodactylus blanci, Acanthodactylus boskianus, Acanthodactylus maculatus, Mesalina olivieri, Ophisops occidentalis), and hyperxeric (Acanthodactylus dumerilii, Acanthodactylus longipes, Acanthodactylus scutellatus, Mesalina guttulata). The analyses also indicated that environment had a weak influence on species richness (15.7% of explained variance), but a strong effect on the phylogenetic (76.5% NTD, 89.5% MPD) structure. The lacertid communities tended to be phylogenetically clustered on sandy substrates under arid climate conditions, and overdispersed under more humid climatic conditions.