REPORT M. J. A. Vermeij Æ E. Sampayo Æ K. Bro¨ker R. P. M. Bak The reproductive biology of closely related coral species: gametogenesis in Madracis from the southern Caribbean Received: 13 August 2001 / Accepted: 29 August 2002 / Published online: 4 March 2004 Ó Springer-Verlag 2004 Abstract Reproductive patterns were studied in closely related coral species of the genus Madracis on Curac¸ao, Netherlands Antilles. Gonadal development of six sympatric species was examined over a 13-month period. Reproductive differences among Madracis species are small. All species are hermaphroditic brooders and show similar patterns in gamete development. Timing of gamete maturation is positively correlated with seawater temperature in all species. Oocyte development typically begins in June and precedes the development of sper- maries. Mature gametes, male and female, are present from August to November when seawater temperatures reach their yearly maximum. Developmental pathways for male and female gametes are identical among spe- cies. Interspecific differences exist in the number and size of oocytes. Our data indicates that differences in game- togenic development between closely related, but eco- logically different subspecies are small or absent and do not necessarily match with species separations based on morphological criteria. Keywords Reef Æ Coral Æ Gametogenesis Æ Reproduction Æ Caribbean Introduction Reproductive strategies are highly variable among scle- ractinian corals. Individual colonies produce either one type of gametes (gonochoric) or both (hermaphrodytic) and fertilization of eggs and subsequent embryonic development can occur either inside or outside the par- ent colony (i.e., brooding or broadcast spawning, respectively). The majority of coral species studied are gonochoric broadcast spawners, while studies on brooding species with either manner of sexual parti- tioning are relatively uncommon, i.e., approximately <10% of all corals studied (Harrison and Wallace 1990, Richmond and Hunter 2000, Veron 2000). Members within a taxon share certain reproductive characteristics and variation is generally largest among species. Such variation in reproductive behavior potentially has eco- logical and evolutionary implications (Futuyama 1992). For some species, insight into interspecific differences in the timing and intensity of gamete production has pro- vided insight into the role of reproduction in coral spe- ciation (Richmond and Hunter 1990, Knowlton et al. 1992, Van Veghel 1994, Tanner 1996). The subtle nature of these differences in reproductive strategies is demon- strated in three members of the Montastraea annularis species complex. Knowlton et al. (1992) found small differences in the time of spawning between different morphs of the Caribbean Montastraea species complex in Panama. A parallel study on Curac¸ao did not find such differences (Van Veghel 1994). Studies of allozymes showed larger genetic differences between Montastraea from Panama compared to Montastraea from Curac¸ ao (Knowlton et al. 1992, Van Veghel and Bak 1993). As a result, the different morphs were classified as different species in Panama but not on Curac¸ao. The lack of temporal reproductive isolation in some corals drives the current debate on the species status of morphological or genetical clusters within existing spe- cies complexes (Veron 1995). Since genetic relationships depend upon the reproductive characteristics of the Communicated by Topic Editor D. Barnes M. J. A. Vermeij (&) Æ E. Sampayo Æ K. Bro¨ker Institute For Biodiversity And Ecosystem Dynamics (IBED), University Of Amsterdam, Mauritskade 57, PO Box 94766, 1090 GT Amsterdam, The Netherlands E-mail: mark.vermeij@noaa.gov Tel.: +1-305 3614230 R. P. M. Bak Netherlands Institute for Sea Research (NIOZ), 1790 AB Den Burg, PO Box 59, Texel, The Netherlands Present address: M. J. A. Vermeij Cooperative Institute for Marine and Atmospheric Science (CIMAS), University Of Miami, 4600 Rickenbacker Causeway, 33149 FL Miami, U.S.A. Coral Reefs (2004) 23: 206–214 DOI 10.1007/s00338-004-0368-z