GENETIC STUDIES OF PATERNITY, LARVAL RELATEDNESS AND LOCAL SCALE POPULATION STRUCTURE: MICROSATELLITE ANALYSIS OF THE CADDISFLY PLECTROCNEMIA CONSPERSA.

H.R. Wilcock^1,2, R.A. Nichols², M.W. Bruford¹, and A.G. Hildrew². ¹School of Biosciences, Cardiff University, Cardiff, Wales, U.K. CF10 3TL, ²School of Biological Sciences, Queen Mary, University of London, London, U.K. E1 4NS

Recent genetic studies have suggested that some freshwater insect populations are founded by only a few adult females. This idea has mainly arisen from the analysis of samples using allozyme markers and from collections of individuals at several spatial scales, local, regional and national. Very few studies have set out to examine genetic variation between individuals at very small scales, within streams, largely because of the need for highly polymorphic genetic markers, such as microsatellites. Until recently it has proved very difficult to isolate these markers for freshwater insects. We have developed microsatellites for the net-spinning caddisfly Plectrocnemia conspersa. Newly hatched first instar larvae spin colonial nets in which to catch their first prey. We aimed to examine the genetic relatedness within and between egg masses laid in the field, as well as changes in larval relatedness throughout the year from oviposition through to late instar. Paternity analysis of reared siblings suggests multiple paternity of egg masses. Relatedness between closely spaced larvae did not suggest that family groups remain together but that siblings quickly disperse away from each other. Microsatellites have also been used to examine gene flow within and between streams over small geographic scales.