The larger the damselfly, the more likely to be threatened: a sexual selection approach

In a changing world due to anthropogenic activities, it is increasingly urgent to identify the biological attributes that predispose species to extinction. Using phylogenetic comparative methods and International Union for Conservation of Nature Red List categories as a proxy for vulnerability to extinction, we evaluated whether body size, sexual size dimorphism and/or mating system (territorial or non-territorial) are linked to extinction risk in 139 damselfly (Odonata: Zygoptera) species. Threatened species of damselflies were, on average, larger than non-threatened species. However, we did not find a relationship between sexual size dimorphism or mating system and extinction risk. Similar to vertebrates and other insects, a large size implies a higher viability costs for damselflies. Other evolutionary mechanisms and not only sexual selection may play an important role in selecting for large body size and rendering larger species more prone to extinction.