Comparison of genetic population structure of endangered Scirpus ancistrochaetus using two methods

Background/Question/Methods

Northeastern bulrush, Scirpus ancistrochaetus, is a federally-endangered emergent sedge, found in wetlands in the Northeast, with a majority of populations in Pennsylvania.  To date, there is no information on the population genetics of this species.  Until we have an understanding of the genetic diversity of this species at local and regional scales, we will not know the extent to which fluctuations in population sizes due to environmental impacts such as climate change, hydrologic changes and increasing canopy cover will negatively impact the conservation of genetic resources in the field.  With over 50% of populations in need of management, population genetics studies can be used to prioritize key areas for management and monitoring.  The goal of this research is to characterize the genetic population structure of this species using two methods.  We collected leaf samples from 26 sites in Pennsylvania, 9 sites in the southern range of S.ancistrochaetus (Maryland, Virginia and West Virginia)  and 13 sites in the northern range of S. ancistrochaetus (Vermont and New Hampshire).  Using DNA sequencing, we identified several SNPs (single nucleotide polymorphisms) that showed variation among the S. ancistrochaetus populations.  The advantage of SNPs and other sequence data is reproducibility, robustness to sample variation and ease of screening once they are detected.  At the same time, we are utilizing RAPDs (Randomly Amplified Polymorphic DNA) to provide additional information on population genetics at a subset of sites.  The use of RAPDs is considered less reliable and robust, yet is easy and relatively inexpensive.  We then compared the resultant genetic structures created from each of the two methods. 

 Results/Conclusions

Within-population genetic variation is low, as predicted for this clonal species.  For between-population variation, genetic structures from methods concur for the most part, with slightly more variation revealed by the RAPDs.  The use of RAPDs may therefore be a viable technique to examine genetic diversity in this species in some cases, such as when resources are limited.  Some populations displayed genetic uniqueness; this information may be used to target sites for protection and management in a way that preserves the full complement of genetic diversity in this species.