Hydroseral habitat requirement of the endangered Shining Ramshorn Snail Segmentina nitida

Abstract

Before the 1950s, the Shining Ramshorn snail Segmentina nitida was widespread across marshes and drainage ditches in Britain, continental Europe and Scandinavia. However, the population has declined rapidly and the IUCN Red Data list highlights the species as seriously vulnerable to extinction. It is now one of the six freshwater molluscan species protected under the UK Biodiversity Action Plan. Most previous research has focused on species decline and conservation issues. The aim of the research reported here was to clarify the habitat requirements of S. nitida in East Kent within the context of a seral classification. Six hydroseral stages were defined according to plant species composition. Segmentina nitida was limited uniquely to the Carex-Juncus-Eleocharis-Oenanthe community, a late seral stage in ditch succession, which confirms the work of other authors. A general linear statistical model applied to data from these sites suggested that (i) the total number of molluscs within each species varied across samples; (ii) the number of molluscs varied between samples with or without S. nitida; (iii) there was no variation in the total number of molluscs across the locations and (iv) there was no relationship between number of molluscs and sample site within location, implying some degree of connectivity between molluscan communities. Also a two-way ANOVA with Factor 1 as the number of mollusc and Factor 2 as the presence/absence of S. nitida showed a significant interaction effect. These observations are novel for these sites in East Kent and have implications for the ecology, life history strategy and conservation management of S. nitida.