ABSTRACT The green algal genus Bryopsis has simple morphology and high phenotypic plasticity, making it difficult to identify its species based on morphological characteristics alone. This study evaluated the diversity of Bryopsis in northeastern Brazil (the State of Pernambuco), based on morphological and molecular data using the markers tufA and rbcL. Molecular analyses were incongruent with morphology, demonstrating the existence of cryptic and polymorphic species in the genus. Of the four taxa cited for the area based only on morphological data (Bryopsis corymbosa, B. pennata, B. plumosa, Bryopsis sp.), only B. pennata was recorded. Typical specimens of B. pennata and B. plumosa were grouped with low genetic divergence, 0-0.21 % for tufA and no divergence for rbcL, indicating that B. pennata is an extremely plastic species that includes specimens with morphotype B. “plumosa”. Bryopsis pennata var. secunda is cited for the first time for northeastern Brazil, with divergence from the typical variety of 0.96-1.57 % for tufA and 0.4 % for rbcL. This study showed that broader sampling of Bryopsis is necessary in order to confirm the taxonomic status of the species referenced for Brazil, whose phenotypic plasticity may cause overestimation of diversity or reveal cryptic species.

Este estudo avaliou a influência da densidade do capim-agulha Halodule wrightii sobre a composição da comunidade algal associada, em habitats rochosos e arenosos da costa do Ceará, Nordeste do Brasil. A comunidade ficológica incluiu 18 espécies em de 10 famílias, integrantes de Rodophyta (72.2%), Chlorophyta (22.2%) e Phaeophyceae (5.5%). A maior proporção foi epilítica (50%), seguida pelas epífitas de H. wrightii (38.4%), epífitas de outras algas (8%) e epipsâmicas (4%). Epífitas de H. wrightii ocorreram associadas com os rizomas, mas gavinhas de H. musciformis ocorreram presas às folhas. A comunidade ficológica variou de acordo com a densidade de H. wrightii independentemente das características particulares dos prados estudados, embora tanto o habitat quanto outras variáveis ambientais pareceram influenciar a composição e diversidade das macroalgas. O habitat rochoso foi mais diverso que o arenoso, mas no habitat arenoso o capim-agulha foi importante para o assentamento de algas em áreas onde substratos duros foram raros ou ausentes.

This study evaluated the influence of the shoot density of the shoal grass Halodule wrightii on the composition of the associated algal community, in rocky and sandy habitats on the coast of Ceará in northeastern Brazil. The phycological community included 18 species in 10 families, members of Rodophyta (72.2%), Chlorophyta (22.2%) and Phaeophyceae (5.5%). The largest proportion were epilithic (50%), followed by epiphytes on H. wrightii (38.4%), epipsammics (8%), and epiphytes on other algae (4%). Epiphytes on H. wrightii occurred mainly associated with rhizomes, but also tendrils of H. musciformis occurred attached to the leaves. The phycological community varied according to the density of H. wrightii, independently of particular characters of the meadows, although both habitat and other environmental variables seemed to influence the macroalgae composition and diversity. The rocky habitat was more diverse than the sandy habitat, but in the sandy habitat the shoal grass was important for algal settlement in areas where hard substrates were scarce or absent.