Population genetic structure in stream insects: what have we learned?
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This chapter synthesizes data from 41 studies on 32 species of stream insects in an attempt to answer three questions: First, what is the major dispersal mechanism in aquatic insects, i.e. stream drift or adult flight? If it is stream drift, then genetic variation would be expected to fit the Stream Hierarchy Model of Meffe and Vrijenhoek (1988). If it is adult flight, populations would be expected to be panmictic at small scales, i.e. among populations in neighbouring catchments. Most stream insects with an adult flight stage do not fit the Stream Hierarchy Model, suggesting that adult flight is the major mechanism of dispersal. Second, at what scale are populations of stream insects structured? Across all studies, there was a signifi cant positive relationship between FST and geographic distance for studies using mitochondrial DNA. The isolation-by-distance relationship for allozyme studies was significant only when studies with high numbers of Hardy Weinberg Equilibrium (HWE) deviations were excluded. Third, what can recent analysis of DNA sequence data contribute to our understanding of historical processes affecting stream insects? Several recent phylogeographic studies using mitochondrial DNA sequence data provide evidence of population and range expansions and contractions, along with past fragmentation, all estimated to have occurred during the Pleistocene.
Aquatic Insects: Challenges to Populations
Population, Ecological and Evolutionary Genetics