Larval gregariousness in Papilionidae is more prevalent outside the tropics

Larval gregariousness, reported for 20 of the 127 families of Lepidoptera, may enhance thermoregulation, feeding efficiency, and antipredator defence. In the swallowtail family (Papilionidae), which is distributed worldwide yet mainly in the tropics, larval gregariousness has independently evolved at least six times. Here we evaluated in Papilionidae whether gregarious species are mostly distributed in temperate regions, where enhanced thermoregulation should be more beneficial because of the colder climate and greater climatic variations, compared to the tropics. We found data for 198 of the c. 560 species of Papilionidae. Results showed that larval gregariousness was significantly more prevalent in temperate regions. This pattern was statistically significant even when the analysis accounted for phylogenetic relatedness, which also influenced the occurrence of gregariousness. Thus, the shared evolutionary history of Papilionidae species explains in part the global distribution pattern of larval gregariousness. Nonetheless, this macroecological pattern of distribution of larval gregariousness in swallowtail species could have resulted from the ecological benefits concerning thermoregulation that are associated with group living.