The Genetic Diversity of Blacknose Dace, Rhinichthys atratulus, on a Micro-Geographic Scale

In this study, we examined the genetic diversity of Connecticut species Rhinichthys atratulus, the Eastern Blacknose Dace, on a microgeographic scale. Previous lab results demonstrated a lack of gene flow among populations of R. atratulus in several river systems. Low gene flow can lead to decreases in population size and a lack of genetic variation. Gene flow between populations can decrease the risks associated with low genetic diversity, and thus is key in understanding a species? potential to deal with environmental change. However, gene flow in previous studies was measured in populations that were relatively far apart. Here, we examined seven microsatellite loci and one mitochondrial gene, nd2, in three adjacent populations of R. atratulus in a tributary of the Connecticut River in Middletown, Connecticut. By looking at gene flow on a microgeographic scale we attempt to find a minimum distance at which populations are genetically homogeneous. Our results show that each of the populations has high numbers of unique alleles and haplotypes, and there are significant genetic differences between sites. Both microsatellite and mitochondrial DNA is evolving under a neutral mode of evolution. These results point to in situ evolution and little gene flow within populations on this scale. This raises interesting questions for conservation of river fish species.