Relating species traits of foraminifera to environmental variables in the Spermonde Archipelago, Indonesia

It is essential to understand how spatial differences in community composition are related to environmental variables in order to explain and predict patterns in biodiversity. We investigated spatial variation in the composition of foraminifera assemblages and assessed the degree to which this could be explained by environmental variables and/or the distance among sample sites. Together, environmental and spatial variables explained 33.5% of the spatial variation in assemblage structure, of which 25.7% was due to environmental variables alone, 2.8% due to spatial variables alone and 5.0% due to covariation of environmental and spatial variables. Associations between the distribution of foraminifera and environmental variables were significantly influenced by species traits. Dinoflagellate symbionts and an orbitoidal chamber arrangement were linked to exposed reefs and a hard substrate, whereas rhodophyte symbionts were linked to sheltered reefs and a sandy substrate. With respect to depth, a hyaline skeletal structure was most strongly associated with deep water, whereas dinoflagellate and rhodophyte symbionts, an orbitoidal chamber arrangement and an imperforate skeletal structure were most strongly associated with shallow water environments. The association with given environmental variables was less pronounced for other traits. Species with spines, for example, were usually restricted to hard-substrate environments, and species with a coin shape to shallow-water environments, but there were species that deviated strongly from this general trend. Results of this study highlight the importance of environment variables in structuring foraminfera assemblages, and further identify traits that appear to influence how species respond to these conditions.