New windows into the secret lives of unionids: Parentage analysis of glochidia

Detailed knowledge of the natural population structure and mating systems of unionid mussels will be key components for their effective conservation and restoration.  Freshwater mussels have a unique life history that involves broadcast spawning, maternal care of larvae, and parasitism on host fish species for larval development and dispersal.  Their broadcasting reproductive strategy provides opportunities for multiple paternity, yet few studies have examined its role or frequency of occurrence in naturally spawning populations.  We are using high-resolution microsatellite genetic markers to assess the genetic structure and diversity within and among several unionid species at hierarchical spatial scales.  As part of this larger study, we are also assessing breeding systems [multiple paternity], male reproductive success, and genetic neighborhoods of gravid females.  Potential patterns of multiple paternity are being assessed in tandem for endangered and common mussel species in several river systems in southwestern Ontario.  As well as requiring the development of novel microsatellite markers, this has involved devising DNA extraction methods for single glochidia in order to obtain multilocus genotypes for assessing paternity.  These results will help inform captive breeding and genetic management of endangered unionids, as well as providing information for mussel restoration efforts.