Defense Seminar - Alex Bybel

Thursday, November 15, 2018 - 10:00am to 11:00am
Event Type: 

Alex’s thesis is titled "Rangewide Genetic Diversity and Population Structure and Within Basin Metapopulation Analysis of the Topeka Shiner (Notropis topeka) " The abstract of Alex’s thesis is included below.

Species and populations with low genetic diversity are at a higher risk of extinction because of an inability to adapt to threats such as environmental change. Human activities have drastically reduced the amount of habitat and the number of populations and connectivity of many species throughout the world. Knowledge of genetic structure and interactions within populations is important for making management decisions for imperiled species. Threatened and endangered species that have experienced a fragmentation distribution can form complete isolated population with no gene flow or metapopulations, which exist as groups of discrete demes that maintain some level of gene flow. The Topeka Shiner Notropis topeka is and endangered cyprinid, native to the Midwestern United States, which has seen drastic reductions in its distribution due to stream alterations eliminating both instream and off-channel, leaving populations fragmented throughout the range.  A total of 9 polymorphic microsatellite loci were used to asses genetic diversity, analyze population structure and compare migration rates across the range and characterize metapopulation structure within some individual populations of the Topeka Shiner. Rangewide analysis of population structure revealed seven distinct populations across the range with moderate levels of genetic diversity, which can serve as management units. Estimates of historical and contemporary migration indicated that populations were significantly more connected thousands years ago whereas current populations have almost no gene flow between them.  These results suggests that human impacts have cause a reduction of genetic connectivity across the range of the Topeka Shiner leaving the remaining populations in geographic isolation. Analysis of genetic structure within two separate basins, The Rock River and Boone River indicated deviations from Hardy-Weinberg Equilibrium, significant genetic isolation by distance and low but significant genetic differences between sites, which suggests that Topeka Shiners in these basins are acting as metapopulations. Both basins formed metapopulations composed of four discrete demes based on genetic variation that were connected by first generation migration. Analysis of migration patterns indicate larger demes may be acting as potential populations sources, which export colonizers to other demes. Although low genetic diversity is not found in most of these populations throughout the range, continual decline of this species will lead to reduced diversity, leaving population susceptible to stochastic events. Given the vast geographical distance between populations natural reestablishment is unlikely in most areas. Managers, therefore should focus on preserving the current genetic diversity across the range by continuing to monitor and improve the amount and distribution of quality habitat to bolster populations of Topeka Shiners, ensuring their survival.