Distribution and zoogeography of cheilostomate bryozoa along the pacific coast of panama: comparison between the gulf of Panama and gulf of chiriquí: Cheilostomes in pacific waters of panama

Abstract

Along the Pacific coast of Panama, bryozoans are often a dominant component in epibenthic communities occupying more space than other taxa. Bryozoans dominate on carbonate substrates such as shells, coral rubble and stones around the islands scattered in the Gulf of Panama and Gulf of Chiriquí, shelves situated in very contrasting environmental settings. A quantitative survey of the encrusting cheilostome fauna occurring in both gulfs was undertaken to study distribution and diversity patterns. Species occurrences were analysed under the context of broader zoogeographic distribution patterns. Both the highest and lowest species richnesses (alpha) were found in the Gulf of Chiriquí whereas the Gulf of Panama showed a moderate richness. The bryozoan fauna in the Gulf of Chiriquí is more abundant and more diverse than in the Gulf of Panama probably due to a higher degree of habitat fragmentation, lower food level and a more stable environment. Q-mode cluster analyses of the 16 most abundant species revealed groupings between the two gulfs (presence/absence) and between shallow and deep sites (absolute abundances). R-Mode cluster analyses of species distribution revealed a Panama and Chiriquí cluster, in which the Chiriquí cluster showed a dominance of species with West Atlantic, Caribbean and Indo-Pacific distribution, whereas the Panama cluster had species known from Atlantic and East Pacific waters.