Land snail dispersal, abundance and diversity on green roofs

Abstract

We present the first major systematic study of land snail diversity on green roofs. We surveyed 27 green roofs and the adjacent ground habitat in six major cities in the southeastern United States. We found a total of 18 species of land snails, with three considered to be non-native, invasive species. The majority of land snails encountered in surveys are widespread, generalist species, typically adapted to open habitats. Twelve of the land snails encountered are \"greenhouse\" species that are very commonly transported via the horticultural trade. Therefore, we infer that at least some land snail species are introduced to green roofs via initial green roof installation and associated landscaping. Additionally, some similarity between roof and ground populations indicates dispersal from nearby ground habitats. The major determinants of snail species diversity and community composition are largely derived from local environmental conditions that are significantly correlated to the quality of green roof maintenance regime and plant diversity. Roof area, height, and age are seemingly not significant characteristics that dictate land snail species richness.