Ecological replication and evolutionary trajectories: managing for evolutionary past, present & future

Authors: Craig A. Stockwell, Michael L. Collyer, Jeffrey Heilveil

Year: 2012 (xliv)

Abstract

One of the challenges for conservation biologists is to conserve both evolutionary legacy and evolutionary potential while allowing populations to evolve in contemporary time. Here, we consider the evolutionary ecology of the White Sands pupfish Cyprinodon tularosa to illustrate the challenges of meeting these three goals. Substantial genetic divergence for many neutral markers, as well as evidence for adaptive divergence in body shape, provides the basis for managing these populations as the Malpais Spring and Salt Creek Evolutionarily Significant Units (ESUs). To further secure the evolutionary legacy of C. tularosa, one conservation action is to establish and maintain refuge populations for each ESU. One such ‘refuge’ population of the Salt Creek ESU was historically established in Mound Spring, an ecologically dissimilar habitat. A microsatellite survey revealed no measurable evidence of genetic drift in the Mound Spring population, but this population has undergone adaptive divergence toward a deep body shape. One approach of providing evolutionary potential is to maintain high levels of genetic variation for the refuge populations by establishing managed gene flow from the ancestral population. Even low levels of managed gene flow, however, can impede local adaptation, so it is prudent to weigh the costs and benefits of gene flow. In the case of Mound Spring, the benefits of gene flow are marginal, but the cost could be substantial if gene flow compromises local adaptation. Thus, the best action may be to treat the Mound Spring population as a separate Management Unit of the White Sand pupfish. More broadly, refuge populations established in ecologically dissimilar habitats have the potential to undergo similar contemporary evolutionary divergence and in the broadest sense, they represent potential incipient species. One could argue that such adaptive diversification may provide unique opportunities for conserving biodiversity during the Anthropocene.