TEMPORAL AND SPATIAL VARIATIONS IN FUNCTIONAL-TRAIT COMPOSITION (FUNCTIONAL DIVERSITY) OF MACROCRUSTACEAN COMMUNITIES IN SEAGRASS MEADOWS

摘要

Functional diversity (FD) is the value and range of functional traits and ecosystem function of organisms present in a community. In marine macrocrustacean communities, FD has traditionally been expressed by taxonomic composition, and patterns of taxonomic richness (e.g.,species richness [SR]) are considered relevant to FD. However, SR is not always used to express FD because there may be overlaps in species' functional roles (i.e., functional redundancy) due to multiple-traits of many macrocrustacean species. This study described the spatiotemporal variations of FD of a macrocrustacean communities using the data collected by 2 spatiotemporal sampling designs in seagrass meadows at the Akkeshi-ko estuary (northeastern Japan) and Tokyo Bay (central part of Japan) along Pacific coast. FDs were measured using ecological multiple-traits such as occurrence, life type, feeding type, and size, a total of 32 categories in 4 functional traits. FD variation was significantly different among areas (tens of km~2). Areas separated into 2 types based on FD variations, i.e.,high-FD areas and low-FD areas. Spatiotemporal variations in FD and SR were compared to determine whether SR patterns are related to variations in FD. The pattern of spatiotemporal variations was different between FD and SR. High SR but low FD (i.e., high functional redundancy) and low SR but high FD (i.e., low functional redundancy) were occasionally found. These results suggest that SR could not be represented as FD in the macrocrustacean community. Evaluation of the functional redundancy in the macrocrustacean community is important to detect patterns of variation in ecosystem function and to identify the ecological determinants of FD.