Meta-analysis of Behavioural Research in Lizards Reveals that Viviparity Contributes Better to Animal Personality than Secretory Glands

Animal personality refers to consistent individual differences across contexts, ecological situations, and/or time. To understand the evolution of animal personality, it is crucial that macroevolutionary patterns be integrated with intraspecific promoters of individual behavioural consistency. In this study, we conducted a meta-analysis to assess the association between animal personality and different indicators of sociability (a personality evolution driver) in a phylogenetic context. In lizards, higher sociability levels have been associated with the presence of secretory glands and viviparity. We analysed behavioural repeatability data from 62 studies, comprising 486 effect sizes, across 37 species, encompassing five categories (activity, aggressiveness, boldness, exploration, sociability), while accounting for phylogenetic constraints. For each species, we gathered data on the number of secretory glands and the reproductive mode (oviparous or viviparous). Results showed similar values of repeatability for species with and without glands and an absence of correlation between the number of glands and repeatability data. However, viviparous species exhibited higher repeatability compared to oviparous species. When conducting separate analyses for each behavioural type, we observed for boldness that species with glands presented higher repeatability in boldness behaviour. Notably, phylogeny played a variable role in shaping repeatability patterns; specifically, only activity and aggressiveness, and to some extent boldness, were influenced by evolutionary history across species. This study underscores the diverse animal personality patterns existing within a broader comparative macroevolutionary framework. It takes into account life history and morphological traits in Squamate lizards, offering valuable insights into these distinctive dynamics.