THE CONSERVATION STATUS OF TEXAS GROUNDWATER OSTRACODA

Abstract Groundwater-obligate organisms are nearly always small range endemic species with a high-degree of imperilment because of a combination of anthropogenic threats and inherent ecological traits such as low reproductive potential. Accurate assessments of conservation status are foundational for development of species-specific research and conservation priorities. Fourteen species of endemic ostracods are restricted to groundwater habitats in Texas. We used NatureServe methodology to evaluate the conservation status of all 14 species. All evaluated taxa were identified as warranting G1S1 (critically imperiled) or G2S2 (imperiled) designation, primarily due to small-range endemism (particularly small area of occupancy and few known occurrences). Most species are recorded from five or fewer locations and occupy 4-km 2 grid cells. Threat levels varied by site type, with all springs and one surface water site facing the most severe threats and highest number of threats. Deeper, phreatic groundwater sites were typically more secure. Most ostracod sites harbor only a single groundwater species, but two sites, Comal Springs and the San Marcos Artesian Well, harbor six and seven species, respectively. Based on this status assessment, we recommend that all 14 ostracod species be designated as species of greatest conservation need (SGCN). Additionally, we propose that the top priorities for these taxa are 1) identification of existing lots in museum holdings, 2) molecular analyses of populations to better delimit species boundaries, 3) additional field work to fully delineate range sizes and area of occupancy, and 4) long-term sampling at diverse sites to track population trends. Supplemental material is available for this article online.