Original paper

The ecology of subdivided populations of a clonal freshwater bryozoan in southern England

Okamura, Beth

Archiv für Hydrobiologie - Hauptbände Volume 141 Number 1 (1997), p. 13 - 34

38 references

published: Dec 23, 1997

DOI: 10.1127/archiv-hydrobiol/141/1997/13

BibTeX file

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Data on patterns of incidence, physicochemical properties of sites, transplant experiments and patterns of reproduction provide insights into the ecology of subdivided populations of the freshwater bryozoan, Cristatella mucedo. Collectively, these data indicate that C. mucedo is distributed as a metapopulation composed of highly clonal sub-populations in the Thames Valley region. Canonical discriminant function analysis of data on water chemistry and site size indicated that physicochemical variables did not discriminate between sites in which C. mucedo was present and absent suggesting that suitable sites are present but unoccuppied as would be expected in a metapopulation. The establishment of transplanted colonies in a previously unoccuppied site provides further evidence that suitable but unoccuppied sites are present in the region. Apparent extinction and colonization events in local populations are consistent with expected dynamics of sub-populations within a metapopulation. Generally low proportions of colonies producing larvae, a short phase of sexual activity, non-detection of sexual activity in many populations, and simultaneous and similar production of asexual (statoblasts) and sexual (larvae) propagules indicate that populations in the Thames Valley region invest predominantly in clonal replication. These high levels of clonality may contribute to metapopulation dynamics by increasing the likelihood of local extinction when populations are challenged by adverse biotic or abiotic conditions. Notable r-selected traits such as rapid clonal growth and massive production of asexual propagules represent a viable ecological strategy for freshwater bryozoans since the relative isolation of habitats allows highly clonal populations to persist through metapopulation dynamics at the regional scale.


physicochemicalfreshwater bryozoanasexualclonalmetapopulationThames Valley