Daniel W. Fong

THE DUAL ROLE OF SELECTION AND EVOLUTIONARY HISTORY AS REFLECTED IN GENETIC CORRELATIONS

The patterns of genetic correlations between a series of eye and antenna characters were compared among two sets of spring‐dwelling and cave‐dwelling populations of Gammarus minus. The two sets of populations originate from different drainages and represent two separate invasions of cave habitats from surface‐dwelling populations. Matrix correlations, using permutation tests, indicated significant correlations both between populations in the same basin and from the same habitat. The technique of biplot, which allows for the simultaneous consideration of relationships between different genetic correlations and different populations, was used to further analyze the correlation structure. A rank‐3 biplot indicated that spring and cave populations were largely differentiated by eye‐antennal correlations, whereas basins were differentiated by both eye‐antennal and antennal‐antennal correlations. Eye‐antennal correlations, which are likely to be subject to selection, were most similar within habitats, which are likely to have similar selective regimes.

Species Interactions in Cave Stream Communities: Experimental Results and Microdistribution Effects

-The interspecific interactions of three pairs of cave isopods and amphipods, previously thought to be competitors, were examined by analyzing washouts and losses from laboratory streams and from manipulation experiments in streams of Organ Cave, West Virginia. None of the pairs were in fact competitors. The isopod Caecidotea holsingeri was an amensalist of the amphipod Stygobromus spinatus in the laboratory, but the two did not interact in the field. The amphipod Gammarus minus was a predator on C. holsingeri both in laboratory streams and in the field, and C. holsingeri was a competitor of G. minus, at least in laboratory streams. Stygobromus emarginatus was an amensalist of G. minus in laboratory streams and in the field; but in the field G. minus was a commensalist of S. emarginatus. This combination of commensalism and amensalism produces the dynamics of a predator-prey system. Interactions in both laboratory streams and cave streams were asymmetric and often had characteristics of several kinds of interspecific interactions. Negative interactions dominated in laboratory streams while positive interactions were more common in the field experiments. Negative interactions had an effect on microdistribution only at the level of individual stones in a riffle. Positive interactions may contribute to the positive association of some species at larger scales.

Small scale and large scale biogeography of subterranean crustacean faunas of the Virginias

Data on number of subterranean crustaceans in river basins, in karst basins within a river basin, streams within a karst basin, riffles within a stream, and rocks within a riffle were analyzed with an emphasis on similarities at different geographic scales. Except at the smallest scale (individual rocks) the coefficient of variation of species number was roughly constant at 0.4, indicating some fractal properties of the variation. Using approximations for the log of the linear extent of each scale, species number increased linearly at a slope of 0.68 (P<0.005). This suggests an unsaturated regional fauna.

Evaluation of eDNA for groundwater invertebrate detection and monitoring: a case study with endangered Stygobromus (Amphipoda: Crangonyctidae)

Effective conservation and management of biodiversity is limited by a lack of critical knowledge on species’ distributions and abundances. This problem is particularly exacerbated for species living in habitats that are exceptionally difficult to access or survey, such as groundwater habitats. Environmental DNA (eDNA) represents a rapid, noninvasive, and potentially cost-effective new tool for detection and monitoring of biodiversity that occur in such habitats. In this study, we investigated the utility of eDNA in detecting the federally endangered Hay’s Spring Amphipod Stygobromus hayi and a co-occurring common congener S. tenuis potomacus from unique groundwater-associated habitats—hypotelminorheic seepage springs—in the Washington, DC metro area. We developed taxon-specific primers and probes for each species to amplify Stygobromus DNA using qPCR. In silico and in vitro validation demonstrated specificity of each designed assay. Assays were then used to screen water samples collected from ten seepage springs. Stygobromus hayi was detected at four seepage springs, including one potential new locality, while S. t. potomacus was detected at four springs, two of which were new localities. This study is the first to our knowledge to successfully employ an eDNA approach to detect rare or threatened invertebrates from subterranean ecosystems. Our study highlights challenges of employing an eDNA approach for the detection and monitoring of invertebrates in groundwater habitats that are difficult to study, including accounting for PCR inhibition and the potential for cryptic genetic diversity.

Terrestrial Fauna in the Greenbrier Karst

The West Virginia cave fauna includes species that leave caves periodically to forage (cave crickets and bats) as well as permanent inhabitants (both species that are limited to caves [troglobionts] and ones that occur elsewhere [troglophiles]). Troglobionts are the best studied, but troglophiles predominate in many caves. Major sources of food for the terrestrial cave communities are transitory organic matter brought in by bats and cave crickets, and riparian deposits along streams. A total of 40 troglobionts are known, 19 of which are endemic to the Greenbrier karst. The highest species richness is in the contact caves and Buckeye Creek drainage in Greenbrier County. Greenbrier County is a hotspot of troglobionts in the USA.

The Subterranean Aquatic Fauna of the Greenbrier Karst

The Greenbrier Karst harbors 16 species of stygobionts known from 92 caves, and six of these caves are type localities of ten of the species. The fauna is dominated by crustaceans and especially amphipods of the genus Stygobromus, and they primarily occupy vadose streams and the epikarst, but are notably absent from phreatic waters. Stygobromus spinaus is the most widely distributed, found in 59 caves. The segmented worm Trichodrilus culeri and the salamander Gyrinophilus subterraneus are both endemic to single site. The amphipod Gammarus minus is the most intensely studied species, but the basic biology of the other species is little known. The Organ Cave system holds the record in species richness (8) and in terms of type locality (3 species) and deserves a coordinated effort for protection.