Long-term effects of sowing high or low diverse seed mixtures on plant and gastropod diversity

Abstract

A number of studies have reported that consumers affect a range of community-level processes, and in turn their diversity and abundance is influenced by the structure and diversity of the plant community. Although gastropods are important generalist herbivores in many environments, few studies have examined the effects of plant species richness and plant community structure on gastropods. This study investigated gastropod species richness and interactions with various above-ground parameters of the vegetation on an experimental field with four plant treatments: low and high diversity of sown later succession plant species, natural colonization at the start of the experiment and natural colonization after 3 years of continued agricultural practice. The investigated gastropod assemblage contained only seven species and was highly dominated by two of them. Both in pitfalls and with hand-sorting the number of species collected per plot was highest in plots with natural plant colonization. Multivariate analysis revealed that overall gastropod abundance was positively associated with plant height and percentage cover of plants, and negatively with percentage grass cover. The same pattern holds for one of the dominant species-complex (Cochlicopa lubrica/lubricella). The other dominant gastropod species (Deroceras reticulatum) was more abundant in samples with higher percentages of moss cover and higher plant diversity, while less abundant at samples with higher plant cover, indicating that the gastropod species preferences may matter more than just their response to plant diversity. Two plant–gastropod species-level associations were observed: Senecio jacobaea with D. reticulatum and Tanacetum vulgare with Cochlicopa spp. The present study also demonstrated that pitfall-traps are suitable for collecting terrestrial gastropods, at least for species-poor grassland habitats. [KEYWORDS: Cochlicopa spp. ; Deroceras reticulatum ; Plant diversity ; Plant–gastropod interactions ; Terrestrial gastropod diversity ; Vegetation structure]