Diversity And Metacommunity Of Benthic Diatoms In The Dong River Watershed

A metacommunity is usually defined as set of well-delineated local communities that areconnected by the dispersal of interacting species. Traditionally, the local habitats in ametacommunity are not directly connected except through the dispersal of organisms. However,dendritic river networks combine characteristics that challenge the traditional conceptual viewsand empirical approaches applied to metacommunities. Due to their dendritic branchinggeometry and stream flow directionality they are strongly hierarchical and asymmetrical. Herewe analyze the metacommunity structure of benthic diatoms in a large scale river system, DongRiver, by applying different spatial eigenfunction models and variation partitioning, to evaluatethe metacommunity structure of dendritic river networks. Main findings:1. In total409diatom taxa were identified during three different seasons, and the highest TrueShannon Diversity Index of a single site was40.74.2. The model that represents hydrological connections between each sites (MEM) betterexplained the diatom community variation than the model that represents overland connectionsbetween each sites (PCNM). The model that reprensents water directionality (AEM) furtherbetter explained the community variation than MEM models, which suggest that the spatialdynamics of benthic diatom metacommunities are mainly confined to the river network andinfluenced by the prevailing water flow.3. Diatom metacommunities in the Dong River watershed are typically shaped by both spaceand environment. Spatial variables further are better in explaining community structure thanlocal environment factors. In the environmental models, variables related to nutrient levels arebetter in explaining community composition.4. Man-made dams have significant effects on the spatial structure of important limnologicalvariables and diatom metacommunity. 5. Functional traits have significant effects on the diatom metacommunity structure.Metacommunities of weakly attached diatoms showed a stronger signature of flow directionalitythan strongly attached diatoms that are expected to be more tolerant to flow-related shear stressand disturbances.