A conceptual model linking demography and population genetics of freshwater mussels

Abstract

Population viability analysis (PVA) provides a mechanism for analyzing extinction risk by considering processes, such as random fluctuation in demographic features, loss of genetic variation, environmental stochasticity, and the occurrence of catastrophes. Freshwater mussels (Unionoidea) are candidates for PVA because of elevated risk of extinction from anthropogenic activities. We designed a stage-based conceptual model summarizing demographic and genetic changes throughout the mussel life cycle that are associated with changes in population size. We discuss what is known about these stages and the processes that affect transitions between stages. Considerably more information is known about adults than other life stages. Much more work must be done on nonadult life stages because they are potentially vulnerable to disruption via environmental degradation, habitat fragmentation, and loss of vertebrate hosts. New approaches, such as development of molecular identification keys, use of microsatellite markers, and assignment tests to measure dispersal, promise to increase our understanding of nonadult life stages, breeding systems, and linkages among populations. Few studies have attempted to use theory from population biology and conservation genetics to gain insight into strategies for effective conservation. We suggest that more work must be done with species that are not yet critically imperiled because study of such species is likely to yield useful data for PVAs and insight into the mechanisms regulating freshwater mussel populations.