Poorly Vetted Conservation Ranks Can Be More Wrong Than Right: Lessons from Texas Land Snails

Setting priorities for scarce conservation dollars requires an accurate accounting of the most vulnerable species. For many invertebrates, lack of taxonomic expertise, low detectability, and funding limitations are impediments to this goal, with conservation ranks usually based on expert opinion, the published literature, and museum records. Because of biases and inaccuracies in these data, they may not provide an accurate basis for conservation ranks, especially when compared to de novo field surveys. We assessed this issue by comparative examination of these data sources in re-ranking the conservation status of all 254 land snail taxa reported from Texas, USA. We confirmed 198 land snail taxa, including 34 new state records. Our assessment of the entire land snail fauna of Texas resulted in (1) a near doubling of recommended Species of Greatest Conservation Need (SGCN) and (2) a 79% turnover in the makeup of SGCN taxa. Field sampling strongly outperformed museum and literature data in the encounter rate of both the entire fauna and all SGCN species, with the latter two demonstrating bias toward larger-bodied species. As a result, conservation priorities based solely on expert opinion and museum and literature records may be more wrong than right, with taxon-appropriate, targeted sampling required to generate accurate rankings.