Late Quaternary reptile extinctions: size matters, insularity dominates

Aim A major Late Quaternary vertebrate extinction event affected mostly large-bodied ‘megafauna’. This is well documented in both mammals and birds, but evidence of a similar trend in reptiles is scant. We assess the relationship between body size and Late Quaternary extinction in reptiles at the global level. Location Global. Methods We compile a body size database for all 82 reptile species that are known to have gone extinct during the last 50,000 years and compare them with the sizes of 10,090 extant reptile species (97% of known extant diversity). We assess the body size distributions in the major reptile groups: crocodiles, lizards, snakes and turtles, while testing and correcting for a size bias in the fossil record. We examine geographical biases in extinction by contrasting mainland and insular reptile assemblages, and testing for biases within regions and then globally by using geographically weighted models. Results Extinct reptiles were larger than extant ones, but there was considerable variation in extinction size biases among groups. Extinct lizards and turtles were large, extinct crocodiles were small and there was no trend in snakes. Lizard lineages vary in the way their extinction is related to size. Extinctions were particularly prevalent on islands, with 73 of the 82 extinct species being island endemics. Four others occurred in Australia. The fossil record is biased towards large-bodied reptiles, but extinct lizards were larger than extant ones even after we account for this. Main conclusions Body size played a complex role in the extinction of Late Quaternary reptiles. Larger lizard and turtle species were clearly more affected by extinction mechanisms such as over exploitation and invasive species, resulting in a prevalence of large-bodied species among extinct taxa. Insularity was by far the strongest correlate of recent reptile extinctions, suggesting that size-biased extinction mechanisms are amplified in insular environments.