Wing morphology and migration status, but not body size, habitat or Rapoport's rule predict range size in North-American dragonflies (Odonata: Libellulidae)

Understanding why species range sizes vary is important for predicting the impact of environmental change on biodiversity. Here we use a multi-variable approach in a phylogenetic comparative context to understand how four morphological, two ecological, and two eco-geographical variables are associated with range size, latitudinal range and longitudinal range in 81 species of North-American libellulid dragonflies. Our results show that: 1) migratory species and species with a more expanded basal hindwing lobe have a larger range size; 2) opposite to Rapoport's rule, latitudinal range is negatively correlated with mid-range latitude; 3) longitudinal range is predicted by wing morphology and migration; 4) body size and larval habitat are not correlated with range size, latitudinal range or longitudinal range. These results suggest that dispersal-related traits, such as wing shape and migratory status, are important factors in predicting the range size of libellulid dragonflies. In addition, the reverse Rapoport's rule suggests that more northern-centred species might be more specialized than more southern-centred species. We suggest that the variables predicting range size are likely imposed by taxon-specific morphological, ecological, physiological and behavioural traits. Taxon-specific knowledge is thus necessary to understand the dynamics of range sizes and is important to implement successful restoration and conservation plans of threatened species.