Relative importance of ecological versus biological traits in driving range sizes of African dragonflies

Aim Ecological traits (e.g. biotope specialisation and habitat preference) and biological traits (e.g. mobility and life history) are highly variable among species. In insect conservation, considerable focus has been on ecological generalisation, with species occupying many biotope types (generalists) often assumed to be widely distributed, whereas species occupying few biotope types (specialists) are assumed as rare and localised. Although this may be valid in most cases, there is an increasing recognition that functional traits, such as insect mobility and life history, have similar importance as drivers of range size among species. Here, we investigate ecological and biological traits simultaneously to determine their relative importance as drivers of range size variation. We hypothesise that ecological traits are primary drivers, whereas biological traits related to mobility and life history are less important drivers of range size. Location Sub-Saharan Africa. Taxon 115 sub-Saharan dragonfly species. Methods Five measures of species range size were obtained from the Odonata Database of Africa. Number of biotope types occupied by adults and larvae, larval habitat preference and adult biological trait information were collated from published sources. We explore the relationships between ecological and biological traits. Using linear mixed models and model averaging, we determine the relative importance of number of biotope types occupied, overall habitat preference and traits related to mobility and life history that drive dragonfly range size while accounting for phylogenetic relationships among focal species. Results Dragonflies occupying more biotope types had wider ranges, although these relationships were overall weak. Dragonflies with longer and later breeding seasons had wider ranges. Overall habitat preference and mobility traits had low importance in our models. Main conclusions Ecological versus biological traits are interactive in shaping the geographical ranges of dragonfly species across Africa. Single traits are weak predictors of species range sizes and we recommend investigating multiple traits simultaneously to improve the accuracy of predictions. In doing so, more informed decisions can be made to ensure effective large-scale conservation of dragonflies.

Automated summary

Ecological and biological traits interact to shape the geographical ranges of dragonfly species in Africa. Single traits are weak predictors of species range sizes, and investigating multiple traits simultaneously is recommended for more accurate predictions.