There is general scientific agreement on the critical role that earthworms play in ecosystems, yet earthworm ecology and diversity are still greatly unknown. This is especially true for the semi-aquatic earthworms of the family Sparganophilidae. These earthworms inhabit the interface of terrestrial and aquatic ecosystems, occurring exclusively in saturated soils or sediments, along the shores of lakes, rivers and wetlands. This endemic North American family comprises eleven species in one genus, and has been virtually ignored in terms of diversity or ecology. Our objective was to determine the habitat preferences, and diversity of sparganophilid earthworms. Three sites (Calhoun, Scull Shoals, and Hitchiti Experimental Forests – all in the Southern Appalachian Piedmont) were selected for this study. At each stream (one small, medium and large at each site), a 50 m transect was placed along the stream bank, and samples (cylindrical, 20 cm diameter and depth) were randomly taken at 10m intervals. These sites were sampled during the spring, summer and fall of 2017. Sediment was collected from summer and fall for particle-size analyses.
Results/Conclusions
Ten species of Sparganophilidae were identified, belonging to three genera, all of which are new to science. Additional collection of the exotic, Eukerria saltensis, was common, and Octolasion tyrtaeum and at least one Amynthas species were also collected, but rarely. At least two species of aquatic oligochaetes were collected as well, one Tubificidae species and Brachyura sowerbyi. The species accumulation curve of sparganophilids did not plateau, suggesting that more species may yet be discovered at these sites. However, only 19% of the specimens were identifiable adults, with most collected only at the spring sampling and none during the fall. This suggests a strong phenology, where reproduction occurs during late winter and/or early spring. Each site had a unique sparganophilid community with no species being shared between sites, suggesting high levels of endemism. We found no difference in abundance was detected between different stream sizes. With this study, the number of sparganophilid species is almost doubled and of genera, tripled. This demonstrates high diversity within a tiny fraction of the distribution of the Sparganophilidae, and emphasizes a critical and evident need for further biodiversity studies focusing on earthworms.