A Comparative Demographic Analysis of Clonal Reproduction in a Temperate Soft Coral

Document Type



Biology (HMC)

Publication Date



In order to evaluate the relative importance of asexual and sexual reproduction to the fitness of a clonal organism, matrix projection models were used to quantify the contributions of each of these reproductive modes to population growth of the soft coral, Alcyonium sp., a species that undergoes frequent colony fission. The demographic and fitness consequences of eliminating either asexual or sexual reproduction from the life cycle of this species were examined by sensitivity analysis and by altering selected entries in the transition matrices to simulate changes in reproductive allocation. Four populations of Alcyonium sp. were monitored photographically for two years to record colony growth, mortality, fission, sexual reproduction, and larval recruitment, Despite high turnover, population densities remained reasonably constant. The 24-52% mortality was matched approximately by recruitment of daughter colonies produced by fission. Sexual reproduction was infrequent, and no larval recruitment was observed. The frequency of both fission and sexual reproduction increased with increasing colony size, while mortality decreased with increasing size. Size-class transition matrices constructed from the demographic data were analyzed by the methods of Caswell (1986, 1989). In both years of the study the size distributions of colonies observed in the field did not differ from the stable size distributions predicted from the projection models. Eliminating sexual reproduction from the life cycle did not alter the predicted stable size distributions; eliminating fission shifted the size distributions of all four populations towards the larger size classes. Reproductive value increased with increasing colony size.

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© 1991 Wiley