Dispersal distances of aquatic insects: upstream crawling by benthic EPT larvae and flight of adult Trichoptera along valley floors

Abstract

Dispersal is an essential process which influences the effects of stream restoration on aquatic insect communities, yet dispersal capabilities of many New Zealand taxa remain unknown. We estimated realised dispersal distances of New Zealand Ephemeroptera, Plecoptera, and Trichoptera taxa by benthic crawling and of Trichoptera by aerial flight in intermittent streams, which are recolonised after every dry period. Benthic crawling distances were not more than 200 m for most genera. In contrast, adult caddisflies were found up to 1500 m from permanent water, with at least one family carrying eggs the full distance. This suggests greater potential for insects to recolonise distant restored sites by aerial dispersal than by crawling. Our results are a first step towards identifying the dispersal pathways used by desired colonist taxa and the distances over which they can disperse. This information will improve our ability to design and implement effective restoration.

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