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Marine Ecology Progress Series

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MEPS 362:149-156 (2008)  -  DOI:

Effects of competition on sexual and clonal reproduction of a tunicate: the importance of competitor identity

Gustavo Muniz Dias1,2,*, Cynthia Grazielle Martins Delboni3, Luiz Francisco Lembo Duarte1

1Departamento de Zoologia, Instituto de Biologia, and 2Programa de Pós-Graduação em Ecologia, Universidade Estadual de Campinas, CP 6109, CEP 13083-970 Campinas, São Paulo, Brazil
3Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão - Travessa 14 Cidade Universitária, CEP 05508-900 São Paulo, São Paulo, Brazil

ABSTRACT: Individual fitness and the structure of marine communities are strongly affected by spatial competition. Among the most common space holders are the colonial ascidians, which have the ability to monopolize large areas of hard substrate, overgrowing most other competitors. The effects of competition on colony growth and on gonad production of the ascidian Didemnum perlucidum were studied in southeastern Brazil by experimentally removing surrounding competitors. Colonies of D. perlucidum competing for space exhibited a growth rate 9 times less than that of colonies that were competitor free. Among the colonies subject to competition, growth rates were unrelated to the percentage of colony border that was free of competitors. However, the identity of the competitor was important in the outcome of border contacts. At the beginning of the experiment, most border encounters of D. perlucidum were with solitary organisms, which in most cases were overgrown. These were progressively replaced by colonial ascidians and bryozoans, resulting mostly in stand-off interactions. Besides reducing asexual growth, spatial competition also affected female gonad production. Colonies free of competitors had a significantly higher proportion of zooids with ovaries. Thus, our findings show that spatial competition reduces both ascidian colony size and gonad production.

KEY WORDS: Space competition · Tunicate · Reproduction

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Cite this article as: Dias GM, Delboni CGM, Duarte LFL (2008) Effects of competition on sexual and clonal reproduction of a tunicate: the importance of competitor identity. Mar Ecol Prog Ser 362:149-156.

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