Does Shell Accumulation Matter in Micro-Scale Land Snail Surveys?

Abstract

land snails are most often surveyed to generate inventories with sites often less than 1 ha in extent and sampling taking place in microhabitats within the site that researchers consider likely to harbor snails (cameron & Pokryszko, 2005; menez, 2001, 2007). the most cost effective approach to site-level sampling has been suggested as a combination of bulk sampling of litter/soil and time restricted search (emberton et al., 1996). this requires a single visit to each site, and the combination of methods enables the investigator to maximize the likelihood of finding both micro (< 5 mm) and macro (≥ 5 mm) snails (solymos et al., 2007). this approach often relies on dead shells as a probabilistic indicator that a given species is present (thurman et al., 2008) because several constraints (remote locations, investigator availability, weather conditions) may not enable surveys to be undertaken during the species’ activity periods. assessing species presence on the basis of dead shells can be realistic, given the rather sedentary and cryptic behavior of land snails, and in most cases gives comparable results at the site scale (rundell & cowie, 2003). recently, there is an increase in surveys that are addressing microhabitat-scale ecological differences regarding the relative abundances and species compositions of communities (e.g., under logs vs. leaf litter) within a site (Kappes et al., 2006; solymos & Pall-Gergely, 2007). taphonomic issues (e.g., differential preservation of shells in different microhabitats) and biases introduced by sampling methods with different selectivity to dead specimens might become increasingly important as spatial scale decreases. We carried out a field experiment in dolines (sinkholes, large karstic depressions) of the aggtelek karst area, hungary, to investigate malacoloGia, 2009, 51(2): 389−393