Island bees: do wood nesting bees have better island dispersal abilities?

Abstract

For bees to reach isolated islands, they need to be able to cross large water barriers. However, functional traits such as nesting behavior, flight range, and body size can limit their dispersal. In this study, the bee faunas of seven different islands or island groups (Anholt, Canary Islands, Fiji Islands, Hawaiian Islands, Madeira, Malta, and Sri Lanka) were analyzed by comparing them to the mainland bee fauna. Nesting strategy and body size for each species were recorded. The relative distribution of traits among the island species were then compared to traits of the mainland species. We found that among islands located furthest from mainland, the proportion of wood nesting bees are higher than for those located closer to mainland, suggesting that wood nesting bees are more capable of island dispersal, most likely due to the associated rafting ability or the ease of being passively transported over water. The body size among the immigrated island species were shown to be commonly of moderate size, while a majority of mainland species were of small size, indicating that moderate sized bees—with longer flight range—were the more likely island migrators. The methods used could be useful for future studies of ecological influences on body size, as well as how other biological traits are adapted for migrant conditions, potentially serving as predictors in regards to climate change, dispersal ability, and control of invasive species.