Latitudinal gradients in body size and sexual size dimorphism in fleas: males drive Bergmann's pattern

We tested for the effects of latitude and geographic range size (GRS) on body size, leg length, and sexual size dimorphism (SSD) across 103 species of fleas, taking into account phylogenetic between-species relationships. When the data on body size were combined for males and females, the positive correlation between body size and latitude, but not GRS, was revealed. When the analysis was restricted to one sex only, the effect of latitude appeared to be non-significant for females, whereas male body size increased with an increase in latitude. Intraspecific body size variation was not associated with either the latitude or the latitudinal span of the geographic range, independently of which data subset was analyzed. No evidence of association between size-independent tibia length and latitude was found for either females, males, or both sexes combined. The degree of SSD decreased with a decrease in latitude but was not affected by GRS. We conclude that macroecological patterns might be manifested differently in males and females. This should be kept in mind while searching for these patterns.

Automated summary

This study examined the effects of latitude and geographic range size on body size, leg length, and sexual size dimorphism in fleas, considering phylogenetic relationships between species. Results showed a positive correlation between body size and latitude, but not geographic range size. Male body size increased with latitude, while the effect of latitude was non-significant for females. Intraspecific body size variation was not associated with latitude or geographic range span. There was no evidence of an association between tibia length and latitude. Sexual size dimorphism decreased with latitude, independent of geographic range size. The findings suggest that macroecological patterns may manifest differently in males and females.