Bryozoan Colonial Growth Form and Habitat Selection

Although the relationship between overall colonial growth form (habit) of a bryozoan and its environment is commonly used in paleoenvironmental interpretations, the specific factors that control habitat selection and subsequent distribution of decoupled character states of growth habits is poorly understood. Studies of a taxonomically and ecologically diverse modern Bryozoa fauna growing on a range of substrates, textures and orientations (natural and experimental) in the Northern Adriatic indicate that environmental scale (km to mm) plays an important role in growth habit distributions. Colonial growth form distributions are associated with substrate complexity as well as substrate type. Standard paleontological and sedimentological sampling methods and protocols may not distinguish among microhabitats which play a key role in the diversity and abundance of specific colonial growth habits. Local growth habit diversity is related to species richness but the relationship is not one to one. Although some species display unique, determinant growth habits, some are plastic displaying multiple growth habits. In addition, common growth habits can be shared by many species even locally.

Methodlogically, a spectrum exists between censusing the abundance of all species in a setting versus the desire of a nonspecialist to infer paleoenvironments based on the presence or absense of decoupled growth form characteristics, e.g. erect vs. encrusting colonies. Our results indicate that the distribution of bryozoan species provides excellent proxies for environment at many scales. Our results also indicate that the presence/absence of decoupled growth form states have little predictive value. The goal is to establish which subset of growth habit characteristics have the greatest predictive value and at which environmental scales.