Effects of Habitat Partitioning on Lizards’ Thermoregulatory Behavior

Habitat partitioning due to species coexistence and its implication for species divergence has been the subject of intense research in evolutionary biology. However, its effect on lizard thermoregulation behavior and effectiveness has largely been neglected. Along with Grigoris Kapsalas, Efstratios Valakos and Panayiotis Pafilis, we recently published a paper in the Journal of Thermal Biology, demonstrating that habitat partitioning is responsible for essential divergence in environmental temperatures, while it also promotes deviations in species thermal preferences and thermoregulatory behavior.

Lake Doxa at Feneos plateau, Peloponnese, Greece (image from: http://www.digiwebart.gr/portfolio_page/der-spiegel-cover-art/).

This work took place in a narrow mountain site in Peloponnese (Feneos plateau, Lake Doxa), Greece. Despite its small size, Greece hosts one of the richest herpetofauna in Europe with a total of 86 species (15 of which are endemic). On top of that, Feneos plateau is an amazing place were 28 reptile species coexist and is the only area in Europe where seven lizards of the family Lacertidae occur in sympatry. The first survey at Feneos plateau started in late 1990s and since then the area attracted many herpetologists from different countries.

For the past 20 years our group has worked on the Feneos broader area studying how resource partitioning shifts dietary preferences, digestive performance and species locomotion. In line with these studies, here we focused on three Podarcis (the most predominant and diversified reptile group in Europe) lizard species–Podarcis peloponnesiacus, P. tauricus and P. muralis–and explored how habitat thermal heterogeneity affects the species’ ability for accurate and effective thermoregulation. To assess our objectives, we compared body temperatures (T_b), operative temperatures (T_e) and set-point body temperatures (T_set) of the three species.

Frequency of field body temperatures (Tb, dark gray) and operative temperatures (Te, light gray). Vertical black solid lines indicate the set-point range temperatures (Tset).

As expected, niche partitioning resulted in differences in the thermal quality of the microhabitats used by the three species, with P. muralis occupying cooler habitats compared to the other two species. The latter resulted in P. muralis being active at lower body temperatures. Yet, all species thermoregulate effectively and keep their field body temperatures close to their preferred temperatures, indicating high thermoregulation accuracy. Interestingly, the preferred temperatures lizards select in the lab were similar for all three species, despite the differences in the microhabitat temperatures and the lower T_b P. muralis achieved in the field. These findings reveal a rather conservative thermal physiology between these three closely related species. We suggest that by selecting cooler microhabitats and being active at suboptimal temperatures, P. muralis probably avoid or reduce competitive interactions with the other two species.

Paper: Sagonas, K., Kapsalas, G., Valakos, E. & Pafilis, P., 2017. Living in sympatry: The effect of habitat partitioning on the thermoregulation of three Mediterranean lizards. Journal of Thermal Biology 65, 130-137.