Studies of Costa Rican Gelidiales (Rhodophyta): four Caribbean taxa including Pterocladiella beachii sp nov.

Eight species within the red algal order Gelidiales have previously been re corded from the Caribbean coast of Costa Rica. In this study morphological observations and analyses of rbcL and LSU gene sequence data were used to d etermine the identity and phylogenetic relationships of four Caribbean spec ies: Gelidium microdonticum, G. floridanum, Pterocladiella bartlettii and P . beachii Freshwater sp. nov. Previous collections of a small Gelidium spec ies from Costa Rica have been referred to either G. microdonticum or the Pa cific species, G. microdentatum. Observations of these previous collections , as well as collections made for this study, verify that they are all G. m icrodonticum. Molecular analyses show that this species has an affinity wit h a group of species predominantly from South Africa and the south Atlantic . We also provide the first report of G. floridanum from Costa Rica. Sequen ce divergence values suggest a genetic discontinuity between Costa Rican G. floridanum and populations from the east Caribbean and western Atlantic. C haracteristics of cystocarp development, as well as the results of molecula r analyses. clearly identify the new species P. beachii as belonging to Pte rocladiella. Morphological and molecular results also indicate that this sp ecies is closely related to P. caerulescens. Pterocladiella beachii may be unique among Pterocladiella species in having a central placental core that is centrally positioned throughout all stages of cystocarp development.