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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. [ABSTRACT FROM AUTHOR]

Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that are accurate to within a few hundred years. In contrast, shells of the genus Mesodon ( Mesodon elevatus and Mesodon zaletus ) contain significant and variable amounts of old carbon, yielding ages that are up to a couple thousand 14 C years too old. Although terrestrial gastropod shells have tremendous potential for 14 C dating loess deposits throughout North America, we acknowledge that accuracy to within a few hundred years may not be sufficient for those interested in developing high-resolution loess chronologies. Even with this limitation, however, 14 C dating of terrestrial gastropod shells present in Mississippi Valley loess deposits may prove useful for researchers interested in processes that took place over multi-millennial timescales or in differentiating stratigraphic units that have significantly different ages but similar physical and geochemical properties. The results presented here may also be useful to researchers studying loess deposits outside North America that contain similar gastropod taxa. [ABSTRACT FROM AUTHOR]

The article discusses a research study on turnover of local-scale fauna on deep seafloor of the Pacific Ocean. Collected were 44 sediment cores for nested square sampling to quantify plant community spatial patterns and species accumulation curves for macrofauna were calculated with Mao's Tau Estimates while multivariate analyses were conducted using nonmetric multidimensional scaling (MDS) to observe sample turnover in multivariate space. Quantified results showed high degree of variability at small spatial scales of faunal composition while nonrandom spatial structure was observed in 20 species contrasting with findings in shallower sites in the Pacific demonstrating a slight difference between species dispersion patterns and random patterns.

Abstract: Fossil shells of small terrestrial gastropods are commonly preserved in wetland, alluvial, loess, and glacial deposits, as well as in sediments at many archeological sites. These shells are composed largely of aragonite (CaCO3) and potentially could be used for radiocarbon dating, but they must meet two criteria before their 14C ages can be considered to be reliable: (1) when gastropods are alive, the 14C activity of their shells must be in equilibrium with the 14C activity of the atmosphere, and (2) after burial, their shells must behave as closed systems with respect to carbon. To evaluate the first criterion, we conducted a comprehensive examination of the 14C content of the most common small terrestrial gastropods in North America, including 247 AMS measurements of modern shell material (3749 individual shells) from 46 different species. The modern gastropods that we analyzed were all collected from habitats on carbonate terrain and, therefore, the data presented here represent worst-case scenarios. In sum, ∼78% of the shell aliquots that we analyzed did not contain dead carbon from limestone or other carbonate rocks even though it was readily available at all sites, 12% of the aliquots contained between 5 and 10% dead carbon, and a few (3% of the total) contained more than 10%. These results are significantly lower than the 20–30% dead carbon that has been reported previously for larger taxa living in carbonate terrain. For the second criterion, we report a case study from the American Midwest in which we analyzed fossil shells of small terrestrial gastropods (7 taxa; 18 AMS measurements; 173 individual shells) recovered from late-Pleistocene sediments. The fossil shells yielded 14C ages that were statistically indistinguishable from 14C ages of well-preserved plant macrofossils from the same stratum. Although just one site, these results suggest that small terrestrial gastropod shells may behave as closed systems with respect to carbon over geologic timescales. More work on this subject is needed, but if our case study site is representative of other sites, then fossil shells of some small terrestrial gastropods, including at least five common genera, Catinella, Columella, Discus, Gastrocopta, and Succinea, should yield reliable 14C ages, regardless of the local geologic substrate. [Copyright &y& Elsevier]

Ecological explanations of the distributions of living things rest on two general conceptual pillars: the niche difference model and the model of spatial and temporal constraint. Both models suggest the underlying importance of spatial distance as a simple correlate of biological pattern. In this essay we discuss five key, but seemingly disparate, conservation issues that have some correlation with or basis in spatial distance. The realization that the world is, at some level, everywhere unique suggests that optimum nature reserve design must find a balance between protecting grain (habitat integrity) and extent (distance). The distance involved in biotic movements helps us define "exotic" and predict invasive risk. The effect of gene movements also has a strong distance correlate, with fitness potentially declining with distance moved (outbreeding depression). Failure to consider spatial variation in disturbance regimes, community composition, and genetic makeup of populations also may hinder restoration. The relevance of reference site information in general decreases as the distance between these sites and restoration areas increases. The distance paradigm we define suggests that there are two inherent bases to conservation: ecology and geography. [ABSTRACT FROM AUTHOR]

The article determines the processes that produce observed patterns by evaluating the spatial distribution of organisms across landscapes. It analyzes the zebra mussel in two lake-rich areas with contrasting invasion histories. The study suggests that similar processes have influenced zebra mussel spread in both landscapes of Belarus and North America.

The article discusses the development of a production-constrained gravity model to forecast zebra mussel Dreissena polymorpha dispersal into inland lakes of some U.S. states. Results showed high correlation of the model with the actual pattern of colonized lakes in southern Michigan and southeastern Wisconsin, and also predicted the colonization of zebra mussel. It concludes the usefulness of the gravity models when dispersal abilities and the attractiveness of potential habitats are known.