Sampling micromolluscs in tropical forests: one size does not fit all

Abstract

Micromolluscs comprise a signifi cant proportion of terrestrial malacofaunas in the tropics. As such, inventories and ecological sampling protocols must endeavor to maximize the capture of micromolluscs. Sampling protocols (i.e., appropriate number of sampling plots) for micromolluscs, however, still require refi nement to improve sampling effectiveness. Apart from describing our recommended sampling protocols for micromolluscs, we compared completeness ratios (as a proxy for sampling effectiveness) and species densities and diversities across different vegetation types (i.e., limestone karst forests [LKFs] and non-limestone karst forest [NKF]) and geographies (i.e., inland and offshore) in Malaysia. Our results showed that completeness ratios at LKFs were signifi cantly higher than NKFs, but no signifi cant differences were detected among plots at inland and offshore localities. In order to optimize resources for sampling micromolluscs, plot sizes at LKFs could therefore be reduced from frequently used 400 m2 plots to 8 m2, while the number of plots at LKFs may range between three to six plots per locality. Having determined that the abundance of micromolluscs in sampling plots was positively correlated with species density, we controlled for abundance and subsequently found no signifi cant differences in micromollusc species diversity between NKFs and LKFs. However, inland localities had signifi cantly higher species diversities than offshore localities. As such, NKFs (due to lower completeness ratios) and offshore localities (due to lower species diversities) probably require more sampling plots to achieve high completeness ratios (and improve sampling effectiveness). Ultimately, the development of a unifi ed sampling strategy must consider variables such as vegetation types and geographies to ensure effective and comparable sampling across a broad array of ecological and geographical situations.