Ditches as important aquatic invertebrate habitats: a comparative analysis of their snail (Mollusca: Gastropoda) assemblages with natural wetlands

Abstract

Wetlands and ditches are both common aquatic habitats in lowland landscapes of northeast China. However, most biodiversity management and research for aquatic organisms has focused on the biota of natural wetlands, and the invertebrate fauna of ditches has not been previously addressed. Because ditch habitats can be so extensive in some landscapes, their contribution could be substantial. To assess the contributions of ditches to invertebrate biodiversity, snail assemblages of natural wetlands, wetland ditches, and agricultural ditches in the Sanjiang Plain of northeastern China were compared. Snail assemblages of the three habitats all differed significantly from each other. Species richness and abundance of snail assemblages in wetland ditches was similar with natural wetlands. Although lower, species richness and abundance of snail assemblages in agricultural ditches still accounted for 22% and 52%, respcetively, of that in natural wetlands. Each of the three different habitats supported unique species, with 11 snail species being indicators of specific habitat types. Biota and Environment matching analysis (BEST) showed that pH in combination with dissolved oxygen were the most important environmental factors in explaining the dissimilarities of snail assemblages among the three different habitats. This study illustrates that both wetland ditches and agricultural ditches make contributions to aquatic invertebrate biodiversity in Sanjiang Plain. More attention should be paid to the importance of ditches as reservoirs for aquatic invertebrates, and the biota of ditches should be considered in the overall scope of biodiversity management and monitoring.