Dr. Rob Dillon, Coordinator

Monday, June 26, 2006

Freshwater Gastropods in State Conservation Strategies - The West

To the FWGNA group:

As most of you will recall, last month I surveyed a set of 10 comprehensive wildlife conservation strategies recently published by states of the southern U.S. I ranked each state by the number of freshwater gastropods on its list of species "prioritized for conservation," relative to its total number of priority species. The resulting ratio, it seems to me, might give some measure of the importance of freshwater gastropods to the overall conservation efforts of each state, and hence (perhaps) the likelihood that grant funding might be available.

This month I've done an identical survey for 12 states of The American West. But before reading any further, I'd challenge each of you to make a prediction. Clearly there is more fresh water in the South than in the West. In which region do you think freshwater snails will attract greater conservation concern?

The answer is in the West, by far. The list below shows that two of the 12 western states did not include any freshwater gastropods in their conservation plans: Montana and Washington. This is identical to the south, where two of 10 states excluded the freshwater snails: Louisiana and Mississippi. But three western states listed eye-poppingly large numbers of freshwater gastropods - 74 (28.1% of all species!) in Nevada, 45 (16.1%) in Wyoming, and 23 (11.7%) in Utah. Among southern states, only Alabama hit the double-digits (11.1%). The average percent freshwater gastropod species on state lists of special conservation concern was 0.070 in the West but only 0.026 in the South.

The difference is largely attributable to endemic hydrobiids. Nevada's 74 freshwater gastropod species of special priority included 61 Pyrgulopsis and 11 species of other hydrobiid genera, almost all narrowly restricted to individual desert springs. Utah's 23 species included 14 hydrobiids, California's 35 included 21 hydrobiids, and hydrobiids comprised all 14 of Arizona's freshwater gastropod species of greatest conservation need.

Many of the lists of the western states also included pulmonate snails, which are rarely mentioned in the south. Idaho and Oregon, for example, were both about equally split between prosobranchs and pulmonates.

A most interesting contrast emerged between the states of Wyoming and Montana. According to the authors of Wyoming's Conservation Strategy, only 44 of that state's 279 species (of all taxa) were listed because of specific, known conservation needs. They stated, "The remaining 235 have been included primarily due to a lack of key data necessary to assess their conservation status." That subgroup of 235 taxa included essentially the entire freshwater gastropod fauna of Wyoming, 45 species in total. In striking contrast, Montana listed only 60 species of all taxa, including no freshwater snails at all. By way of explanation, the authors of the Montana Strategy wrote, "Most invertebrates were not included in the assessment due to lack of data.

"Below are the 12 states of the American West, ranked by the conservation concern they directed toward their freshwater gastropod faunas. As I mentioned last month, some states do appear to be accepting outside proposals for grants to study their species of greatest conservation need. Good luck to all of you!

And keep in touch,