Bryozoans, space and time
CEES Extra seminar by Paul D. Taylor
Bryozoans are a phylum of predominantly marine invertebrates that are entirely colonial, all species developing colonies of between a few and many thousands of clonal zooids. The majority of species are sessile encrusters of hard or firm substrates such as shells, rocks and marine plants. Competitive interactions for substrate space are readily observable when colonies come into contact with other bryozoans or different organisms cohabiting the same substrate. Overgrowth normally ensues, the loser suffering total or partial mortality. Success in spatial competition appears to be improved by several morphological traits but interactions between species may be complex: simple, predictable competitive hierarchies are seldom apparent. The importance of spatial competition in structuring marine benthic communities remains unclear, as is its role as a selective force driving bryozoan evolution. Nevertheless, because bryozoans normally have fossilizable skeletons of CaCO3, ancient competitive interactions can be frozen in time, offering a rare opportunity for studying competition in the deep geological past.
Paul D. Taylor
Department of Earth Sciences, Natural History Museum, London SW7 5BD