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Disturbance, colonial fragmentation, and dependent life history variation in two coral reef cnidarians

1986; Inter-Research; Volume: 28; Linguagem: Inglês

10.3354/meps028245

1616-1599

RH Karlson,

Crustacean biology and ecology

Fragmentation can be a crucial part of the life history of colonial invertebrates inhabiting disturbed environments.In some colonial species, fragments may be generated solely by external forces.In others, fragmentation may be facilitated by the degeneration of skeletal or soft-tissue connections between individuals.Colonies of 2 abundant coral reef zoanthid species, Zoanthus sociatus and Z. solanderi, occur as highly fragmented aggregations of polyps with mean sizes between 1.7 and 4.5 polyps per fragment.These are among the smallest fragments for colonial species which maintain connections with their asexual offspring.These data are consistent with the notion that at least some of the fragmentation in these species is under endogenous control.In spite of living in a physically more benign habitat, Z. solanderi had more highly fragmented colonies than did Z.sociatus.Generally, the life history of fragmenting colonial invertebrates includes high colony mortality and delay of sexual reproduction among small colonies.Colony size-specific data from Z. sociatusconform with these expectations.Z. solanderi, on the other hand, appears to have reduced some of the usual costs associated with small colony size.It exhibited lower size-dependent mortality than did Z.sociatus and underwent some sexual reproduction among small colonies.The adaptive trade-off between colonial fragmentation and integration may involve a balance between local and much larger scale sources of mortality.Major catastrophic events are likely to favor genet fragmentation and the spreading of risk.The degree of fragmentation, however, may be limited by small-scale, sizedependent mortality.