MEPS 348:213-220 (2007)  -  DOI: https://doi.org/10.3354/meps07067

ABSTRACT: Using morphological variables to describe how species coexist within morphospace, previous studies have shown that species-rich assemblages can (1) show no morphological overlap between species, and (2) occupy a larger morphospace than species-poor assemblages. To describe morphospace occupation in bivalve species from a species-rich tropical (Roebuck Bay, northwestern Australia) and a species-poor temperate (Wadden Sea, The Netherlands) intertidal flat, we used a functional trait that has a clear ecological interpretation: bivalve feeding morphology. Bivalve feeding morphology can be represented by the dimensionless log-ratio of the size of the pumping apparatus (gills) to the size of the sorting apparatus (palps). This log gill-to-palp mass ratio is tightly related to both feeding mode and environment. At both intertidal flats, the log gill-to-palp mass ratios of all species sampled fell along a continuous gradient from those typical of deposit feeders to those typical of suspension feeders. Surprisingly, the log gill-to-palp mass ratios of the species-rich assemblage at Roebuck Bay displayed greater morphological overlap within a larger total occupied morphospace than the species-poor assemblage at the Wadden Sea. The larger total morphospace at Roebuck Bay appears to reflect greater species richness and broader environmental ranges. Because gills and palps of bivalves are easily measured, we propose that they provide a basis for further morphospace comparisons among communities, e.g. along entire latitudinal, depth or productivity gradients.

KEY WORDS: Morphology · Functional trait · Bivalve · Ctenidia · Labial palps · Community structure · Diversity · Morphospace