Climatic niche differences among Zootoca vivipara clades with different parity modes: implications for the evolution and maintenance of viviparity.

Parity mode (oviparity/viviparity) importantly affects the ecology, morphology, physiology, biogeography and evolution of organisms. The main hypotheses explaining the evolution and maintenance of viviparity are based on bioclimatic predictions and also state that the benefits of viviparity arise during the reproductive period. We identify the main climatic variables discriminating between viviparous and oviparous Eurasian common lizard (Zootoca vivipara) occurrence records during the reproductive period and over the entire year.Analyses based on the climates during the reproductive period show that viviparous clades inhabit sites with less variable temperature and precipitation. On the contrary, analyses based on the annual climates show that viviparous clades inhabit sites with more variable temperatures.Results from models using climates during reproduction are in line with the "selfish-mother hypothesis", which can explain the success of viviparity, the maintenance of the two reproductive modes, and why viviparous individuals cannot colonize sites inhabited by oviparous ones (and vice versa). They suggest that during the reproductive period viviparity has an adaptive advantage over oviparity in less risky habitats thanks to the selfish behaviour of the mothers. Moreover, the results from both analyses stress that hypotheses about the evolution and maintenance of viviparity need to be tested during the reproductive period.