The latitudinal patterns of phylogenetic, functional, and numerical interaction specificity in flea–mammal networks vary between biogeographic realms

The latitudinal patterns of the phylogenetic, functional, and numerical interaction specificity (PIS, FIS, and NIS, respectively) of fleas and mammals in their interaction networks, from four biogeographic realms, were investigated at the intraspecific, interspecific, and community levels to understand whether the spatial variation of interaction specificity followed the predictions of a latitudinal specialization gradient.In fleas, no latitudinal pattern of PIS was detected.Flea FIS varied with latitude in all realms at the intraspecific level and in two realms at the interspecific and community levels.Latitudinal trends in NIS were detected in all realms (except Neotropics) at the intraspecific level and in the Old World realms at both higher levels.In hosts, PIS varied with latitude in the Afrotropics and the Nearctic at the intraspecific level and in the Afrotropics at the interspecific and the community levels.FIS demonstrated a latitudinal trend in the Nearctic at the intraspecific level and in the Palearctic at the community level.Relationships between latitude and NIS were found in all realms (except Neotropics) at the intraspecific level and in the Old World realms interspecific and https://doi.org/10.1017/S0031182026102182