The endangered fairy shrimp (Branchinecta sandiegonensis). Photo credit: D. Parsick, University of San Diego

There are three species of Branchinecta fairy shrimp in southern California, the federally endangered Branchinecta sandiegonensis, the federally threatened Branchinecta lynchi and the more common Branchinecta lindahli which overlaps in distribution with B. sandiegonensis and B. lynchi. Currently, these three species can only readily be distinguished based on morphological characteristics of adults. 

We are developing a rapid genetic test for species identification from cysts which will allow assessment of species presence during the dry season (cysts are present in soils year-round), as well as for verification of morphological identifications of adults.

More information can be viewed at http://www.werc.usgs.gov/sandiego/gen_FairyShrimp.html. For more information contact Amy Vandergast, Western Ecological Research Center.

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Horseshoe crabs on Florida shore. Photo credit: Thomas A. Hermann/NBII.Gov

Thirteen microsatellite DNA loci were surveyed in 1232 horseshoe crabs (Limulus polyphemus) collected from 28 spawning sites ranging from Franklin, ME to the Yucatan Peninsula, Republic of Mexico.  This range-wide survey revealed a high degree of genetic diversity (up to 50 alleles per locus) and heterozygosity (up to 97.2%).  There appeared to be substantial gene flow between each population and its nearest neighbors.  The correlation of genetic distance and geographic distance supported isolation-by-distance as a mechanism underlying structure of L. polyphemus along the Atlantic coast of North America.  Results suggested the presence of male-biased dispersal throughout the study area.  Within the continuum of isolation-by-distance and in the presence of male-biased dispersal, clustering of specific collections on a tree of genetic distances and hierarchical gene diversity analyses demonstrate discrete regional units.  These results suggest the definition of five regional management units within the United States:  Gulf of Maine, Mid-Atlantic, Southeast U.S. (South Carolina and Georgia), Florida-Atlantic, and Florida-Gulf.  Multilocus assignment tests indicate a high probability of correctly assigning individuals back to the proposed management unit from which they were collected, and could serve as a useful tool for identifying the source of animals that are caught at sea.  This mixed-stock research is currently underway.

For more information contact Timothy L. King at the Leetown Science Center.

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Mahogany Jerusalem Cricket. Photo credit: David Weissman, California Academy of Sciences

Habitat loss and fragmentation due to urbanization are some of the most pervasive threats to biodiversity in southern California. Loss of habitat and fragmentation can lower migration rates and genetic connectivity among remaining populations of native species, reducing genetic variability and increasing extinction risk. USGS scientists and colleagues have examined genetic variation in remnant populations of endemic Jerusalem crickets. These are large, flightless insects that are found throughout southern California, and are ideal indicator species for monitoring the effects of urban habitat fragmentation. Results show that genetic connectivity has declined across urban barriers such as housing developments and roads. Smaller and more isolated fragments also contain populations with less genetic diversity than those in larger and more contiguous natural areas. Although efforts to restore connectivity among natural areas in southern California are usually focused on larger, wide ranging species, our results also underscore the importance of preserving and restoring landscape connectivity for long-term persistence of smaller native species with low mobility and small home ranges.

For more information view http://www.werc.usgs.gov/sandiego/JC_page.html and http://www.werc.usgs.gov/sandiego/SAMOPage.html and contact Amy Vandergast, Western Ecological Research Center.

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Madison cave isopod. Photo credit: Courtesy Virginia DCR Natural Heritage Program

Antrolana lira is a subterranean freshwater crustacean (stygobite) endemic to the karst aquifers of the Shenandoah Valley in Virginia and West Virginia. A. lira was listed as a threatened species in November 1982 primarily due to the groundwater threats posed by urban and agricultural development combined with the absence of basic life history and ecological information on the species.  A detailed understanding of the evolution of the Shenandoah Valley hydrogeologic system is essential to identifying additional populations, developing management and recovery plans for Antrolana lira. In a karst setting, typified by sinkholes, subterranean water-filled conduits, springs and caves, historic groundwater flowpaths can play a significant role in understanding modern hydrologic connections because those flowpaths may still be used during high flow events, directing water across what are, during normal aquifer levels, drainage divides.  These historic connections and high-flow routes can be difficult to detect during standard hydrogeologic examinations that include techniques such as potentiometric surface mapping, dye tracing, and karst feature mapping.  Traditional methods of mark and recapture in subterranean organisms provide limited details about the migratory patterns of a species because so few marked individuals are ever recaptured. Advances in genetic analysis are increasing our ability to detect patterns of connectivity.  The genetic history of stygobite gene flow patterns could be a valuable tool to add to the standard hydrogeologic methods toolbox.  Genetic techniques can provide population-specific data (e.g., levels of genetic diversity, genetic variation, and effective population sizes) and the migratory routes connecting populations.

For more information contact Timothy L. King at the Leetown Science Center.

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