Assessing community functional attributes during substrate colonization: a field experiment using stream insects

Abstract

Initial colonists of empty habitats tend to differ from those arriving later in terms of species identity and traits. We evaluated the dynamics of the functional attributes in aquatic insect communities during a colonization experiment under natural conditions. We tested whether the late stages of colonization show higher functional richness, diversity and specialization than early successional stages. We used 60 artificial slate samplers that were removed after 1, 3, 5, 10, 15 and 30 days of colonization. We considered five traits (with a total of 17 trait categories): feeding habits, dispersal medium, body size, body shape and locomotion. With these traits, we computed a global specialization index at the community level. Large shredders with a cylindrical body shape and fly dispersal while flying were prominent in late colonization. In contrast, early colonists tended to have flattened body and to disperse through water. Functional diversity and functional richness significantly increased in late colonization, resulting in a more specialized community. Our results suggest that any interference during the processes involved in stream insect colonization can be reflected in the community through the decrease or even lack of functional attributes.