Ecological, genetic and morphological differences among Pavona (Cnidaria: Anthozoa) species from the Pacific coast of Panama

On the Pacific coast of Panamá, corals of the genus Pavona can be separated into two morphological groups based on the presence (Pavona varians, P. frondifera, and Pavona sp. a) or absence (P. gigantea, P. clavus, P. maldivensis, and Pavona sp. b.) of collines. Pavona sp. a and Pavona sp. b are new species. The latter species is described herein. I studied the ecological, genetic, and morphological differences among species in these two morphological groups of Pavona to determine their specific differences. Ecological information included geographical distributions of species, habitat preferences, interspecific interactions, reproductive ecology, and tolerance to bleaching. Assessment of genetic differences was based on the electrophoretic analysis of 10 allozyme loci. Morphological analyses consisted of tissue coloration, colony morphology, and measurements and counts of 8–10 skeletal characters. Pavona gigantea, P. clavus, and P. varians are the most widely distributed, being found at 40 (88.9%), 34 (75.6%) and 19 (42.2%) of 45 sites surveyed. Pavona sp. b and P. frondifera have much narrower distributions (1–3 sites). Pavona maldivensis was not found during this study. There are no specific habitat preferences for most Pavona species (reef and inter-reef habitats) except for Pavona sp. a, and P. frondifera, which lives in basaltic rocky habitats and on reefs, respectively. In an aggressive interaction hierarchy, most Pavona species are subordinate to P. varians. Only P. varians and Pavona sp. a have been observed to spawn in Panamá. These species show marked differences in their reproductive biology. The four Pavona species influenced by the 1997–98 El Niño suffered differential bleaching and subsequent mortality to the sea warming: Pavona sp. a (least resistant) > P. clavus > P. varians > P. gigantea. Allozyme patterns in species with ridges show a fixed difference between P. varians + P. frondifera and Pavona sp. a at the triose phosphate isomerase (TPI-2) locus. Nei's unbiased genetic distances between Pavona sp. a and Pavona varians and P. frondifera are 0.435 and 0.379 respectively. Pavona varians differed slightly from P. frondifera at a genetic distance of 0.068. Only significant gene frequency differences were found at most loci examined between species lacking ridges. Pavona gigantea differed strongly from P. clavus and Pavona sp. b, with a genetic distance of 0.248 and 0.396 respectively. Pavona clavus differed greatly from Pavona sp. b with a genetic distance of 0.293. There is considerable inter- and infra-colony morphological variation in Pavona: P. varians (most variable) > P. gigantea > P. clavus > Pavona sp. b > P. frondifera > Pavona sp. a. Non-skeletal characters figured prominently in the identification of Pavona sp. a and P. gigantea. Tissue coloration is diagnostic for Pavona sp. a and highly informative for P. gigantea. Also polyp expansion in P. gigantea is unique, occurring during the day. Canonical discriminant function analysis readily separates the species within each of the morphological groups. In conclusion, all six studied Panamanian Pav...