Ecological and evolutionary concerns in freshwater bivalve relocation programs

Relocation of native freshwater bivalves has been used as a conservation to ol primarily for restorative or supplemental reasons and to remove populati ons from the immediate impacts of construction projects. Though the presenc e of indigenous bivalves was most often used as an indicator of suitable ha bitat to receive relocated animals, subtle ecological and evolutionary diff erences between communities may have precluded successful relocation. We di scuss the importance of maintaining genetic diversity within and among popu lations, the potential for spread of disease causing pathogens and parasite s, and suggest approaches that could lead to improved relocation success, w ith the ultimate goal of maintaining the evolutionary lineages of freshwate r bivalve species. Conservation efforts should strive to ensure that geneti c variation is preserved to maintain the potential for future evolutionary change, and intervene as little as possible when managing the genomes of th reatened species. However, when relocations are deemed necessary, every pre caution should be taken to minimize the effects of gene drift and inbreedin g depression by providing sufficiently large effective population sizes. Th ose involved in relocations should also exercise vigilance to avoid the pit falls of outbreeding depression resulting from mixing divergent evolutionar y lineages and the potentially catastrophic consequences of introduced path ogens. In addition, relocation attempts to supplement population size and m aximize genetic diversity of historically small populations may lead to the loss of critical adaptive features including the relationship established with the parasitized host(s). Management efforts that focus on the protecti on of existing populations, and the discovery and protection of new populat ions of threatened taxa, may represent a more realistic conservation strate gy than the creation of populations of unknown ecological and evolutionary potential.