ORIGINAL ARTICLE: Are small sedentary species affected by habitat fragmentation? Local vs. landscape factors predicting species richness and composition of land molluscs in Swedish conservation forests

Abstract

Aim To investigate the relative role of local versus landscape factors for local species diversity of snails and slugs in conservation forests. In landscapes with small, isolated patches of semi‐natural habitats, many species that require large habitat areas have disappeared or are threatened. We asked whether small sedentary taxa that depend on local conditions, such as molluscs, are affected if total habitat area decreases in the landscape. Location Temperate broadleaved and oak‐rich forest in southern Sweden. Methods We sampled molluscs in 25 small conservation forests that are well‐spaced out over a large region. In each forest, sampling was conducted in two plots, each of 1 ha, separated by about 25–100 m. Factors potentially influencing local diversity of molluscs were measured in the plots and in the surrounding landscape at different scales (in space and time) and were analysed by stepwise multiple regression and ordination (PCA and NMS). Results We recorded 53 species, and mean species richness per forest (plots pooled) was 22.6. The pH of the plant litter predicted both species richness and composition; other local (plot) factors of lower importance were canopy openness, stony ground and tree species. The area of conservation forest (woodland key habitat) within 10 km of plots was positively associated with species richness, and was also related to species composition. Openness of the landscape (agriculture) was a negative factor, but historical plot openness (1938–59) seemed to be unimportant. In addition, climate/topography (temperature and altitude) also predicted species composition of the sites. Main conclusions We rejected the hypothesis that microhabitat factors alone, or mainly, determine local species richness and composition of land molluscs. These representatives of small, sedentary organisms seem to be substantially influenced by the surrounding landscape, which should be considered in conservation work and in plans for the protection of forest biodiversity.

Biodiversity conservation across taxa and landscapes requires many small as well as single large habitat fragments

“…This was confirmed by the result of Mantel tests which showed that the species composition of plants, leafhoppers and true bugs on each fragment was highly correlated (Su et al 2004; but see Dormann et al 2007). In contrast, snail community composition was only weakly correlated with that of leafhoppers, presumably because of the high dispersal limitation in snails (Götmark et al 2008). Also, since the fragments did not display a nested species composition, i.e.…”

“…This can be explained by their low mobility, making connectivity and the surrounding landscape less important for them. They can be expected to be more influenced by local habitat factors like management and management history (Boschi and Baur 2007; but see Götmark et al 2008).…”

Locomotor activity of two sympatric slugs: implications for the invasion success of terrestrial invertebrates

“…Indeed, Honek and Martinkova (2010) showed that the invasive slug A. lusitanicus prefers to hide in dense stands of grass like the sown wild flower area from where it spreads into bordering fields or habitats for feeding. On the other hand, on a landscape scale, habitat fragmentation has been shown to negatively affect gastropod species (Gotmark et al 2008, Kappes et al 2009). In general, the strength of fragmentation effects depends on the mobility behavior of the species (Ewers and Didham 2006).…”

A long-term influence of anthropogenic alkalization on molluscs biodiversity in an area affected by cement industry, Świętokrzyskie Mountains, South-Central Poland

“…Snail studies conducted in different forest associations (Addison andBarber 1997, Niemela 1997) indicated that terrestrial snails were strongly dependent on litter composition and were the most abundant in multispecies deciduous forests. According to Götmark et al (2008), studies carried out in 25 forest reserves indicated that pH of the litter was the most important factor decisive for the composition and abundance of snails. The malacofauna of the Malik Hill inhabits three different plant communities (hornbeam-beech woods, coniferous forest and meadow) growing on distinct soil types: rendzinas developed on Devonian dolomites, sandy rusty podzolic soils and gley soils which have been exposed to anthropogenic pressure for many years.…”