PHYLOGENY AND REPRODUCTION IN SYLLIDAE (POLYCHAETA)
Nygren, A.
Department of Marine Ecology, University of Gothenburg S-413 90 Gothenburg, Sweden
Address for correspondence: Swedish Museum of Natural History, Zoo-tax, S-10405 Stockholm, Sweden.
The phylogeny of 12 representatives of the four syllids subfamilies are analysed using 43 morphological characters and 93 character states. The analysis is designed to answer two questions: are the four subfamilies monophyletic, and how are the different reproductive modes related? Syllids show two modes of reproduction, epigamy and schizogamy. In epigamy the whole animal is involved in reproduction with development of extra bundles of chaetae and changes in musculature and sense organs. Epigamy is constrained to three of the four subfamilies, Eusyllinae and Exogoninae and also in some members of Autolytinae. In schizogamy the main animal buds of sexual individuals that swim to the surface and spawn. Schizogamy is found in Syllinae and Autolytinae. Several modes of brood protection also occur in the family; in epigamous species the embryos are attached to the main animal, whereas in schizogamous species the stolon care for the young. Brood protection appears in Eusyllinae, Exogoninae and Autolytinae. The resulting tree indicate that members exhibiting brood protection are constrained to one clade, and that it is uncertain whether epigamy or schizogamy is the plesiomorphic reproductive mode. Three of the four subfamilies, Autolytinae, Exogoninae and Syllinae, are supported in the analysis whereas Eusyllinae is found to be polyphyletic.