Knowledge of community structures is essential for both basic science and applied problems such as conservation and future prediction. One of the main objectives of community ecology is to clarify the mechanisms that determine community structures. Recent studies in community ecology have emphasized the importance of macroecological processes such as biogeographical processes and phylogenetic variation in component species even at local scales. Biogeographic affinity has been utilized to understand community assembly processes, reflecting limitations by geological and phylogenetic histories in terrestrial communities such as altitudinal zonation in montane ecosystems, but has rarely been applied to marine communities.
We examined the effects of environmental variables and biogeographic affinities of component species on a benthic community in a continuous river–estuary–bay water system in Akkeshi, northeastern Hokkaido, Japan. Gammaridean amphipods were used as a model taxon because they are known as one of the major components of macrobenthic communities and have low dispersal abilities.
Our previous study (Sekioka et al., in review) has shown that the amphipod community structures, represented by the presence/absence of species, are influenced by both environmental variables and the biogeographic affinities of component species in a continuous water system in Akkeshi. However, quantitative relationships between the abundance of the species and the suggested factors remain unknown. In this study, we examined the effects of environmental variables and biogeographic affinities on amphipod community structures using quantitative data.
We chose a continuous water system comprising Bekanbeushi River, Akkeshi-ko estuary, and Akkeshi Bay in Akkeshi as the study area. Data sampling in the river was conducted from June to October 2020. Sampling in the estuary was conducted in August and September 2020. Sampling in the bay was conducted from April 2020 to March 2022. Amphipods were collected using hand net in the river, sledge net in the estuary, and sledge net and dredge in the bay, then identified to the lowest taxonomic level based on their morphology. Depth, water temperature, salinity, and sediment type were measured after amphipod collection, and their relationships with the amphipod community structures were examined using distance-based redundancy analysis (db-RDA). The biogeographic affinities of the identified species were defined based on their correspondence of global occurrence records with the Marine Ecoregion of the World (Spalding et al., 2007) and were analyzed for their relationship with occurrence trends in Akkeshi. We will present the results of the analysis and further discussions.