REEF CORAL REPRODUCTION IN THE EASTERN PACIFIC - COSTA-RICA, PANAMA, AND GALAPAGOS-ISLANDS (ECUADOR) .2. PORITIDAE

A comparative study of the reproductive ecology of the zooxanthellate, scleractinian corals Polites lobata Dana and P. panamensis Verrill wa s conducted from 1985 to 1991 in eastern Pacific reef environments tha t were severly impacted by the 1982-1983 El Nino warming event. P. lob ata, a presumed broadcast spawner of large colony size, is widely dist ributed in the equatorial eastern Pacific, whereas P. panamensis, a br ooder of small colony size, is abundant only on some reefs in Panama. Both species were gonochoric with nearly 1:1; sex ratios in large stud y populations except for P. lobata at Cano Island that had 14% hermaph roditic colonies. Mature, unfertilized oocytes contained numerous zoox anthellae in both Polites species, and all planula developmental stage s contained zooxanthellae in P. panamensis. Year-round sampling reveal ed high proportions of colonies with gonads, ranging from 30 to 68% in P. lobata and from 60 to 86% in P. panamensis. No clear relationship between numbers of reproductive colonies and the thermal stability of the habitat was evident in P. lobata: percent colonies with gonads at non-upwelling sites was 48 to 68% at Cano Island (Costa Rica) and Uva Island (Panama), and at upwelling sites 30 to 50% at Saboga Island and Taboga Island (Panama), and the Galapagos Islands (Ecuador). Similarl y, 90% of all P. panamensis colonies were reproductive at Uva Island ( a non-upwelling site), and 86% were reproductive at Taboga Island (an upwelling site). Upwelling at Taboga Island is seasonal, nevertheless P. panamensis produced mature gonads or planulae over most of the year (11 mo), whereas P. lobata exhibited reproductive activity during onl y 2 mo (May and June). No clear lunar periodicity was observed in P. p anamensis (Taboga Island), but a high proportion of P. lobata showed i ncreased gonadal development around full and new moon, especially at C ano and Uva Islands. Estimated fecundities were relatively high for P. lobata at Cano (4000 eggs cm(-2)yr(-l)) and Uva (5200 eggs cm(-2)yr(- 1)) Islands, and notably low (70 to 110 eggs cm(-2)yr(-l)) in the Gala pagos Islands. P. panamensis mean fecundity at Taboga Island was 720 p lanulae cm(-2)yr(-l) or 4.0 mm(3) cm(-2)yr(-l), which was lower than t he egg volume production of P. lobata at Cano and Uva Islands (7.0 to 10.0 mm(3) cm(-2)yr(-1)). The capacity of P. lobata and P. panamensis to reproduce sexually supports the notion that eastern Pacific coral r eef recovery may not be dependent on long-distance dispersal from cent ral Pacific areas. However, sexual recruits of P. lobata are absent or uncommon at all eastern Pacific study sites while recruits of P. pana mensis were common to abundant only at the Uva Island study site. Asex ual fragmentation in P. lobata augments recruitment locally, but plays no role in P. panamensis recruitment.