Estudo taxonômico da ordem Dictyotales (Phaeophyceae - Heterokontophyta) no litoral do estado de Alagoas - Brasil

Abstract

The Dictyotales order (Phaeophyceae) is distributed in temperate and tropical flora. In Brazil, they occur from Maranhão to Rio Grande do Sul, besides Atol das Rocas and the archipelagos of Fernando de Noronha and Trindade. In the Northeast, this order is the most significant in numbers of species within the Phaeophyceae. Given its importance, this study aimed to make the taxonomic and floristic study of the order on the coast of the state of Alagoas, which has a great phycological diversity. Four sampling stations were selected along the coast. Samples were collected seasonally in the dry and rainy season, during low tides, in the intertidal zones using a spatula and/or in free dives. The collected material was fixed in 4% formalin and transported to the Federal Rural University of Pernambuco (UFRPE). The taxonomic identification was based on morphological and anatomical characters and was confirmed by specialized bibliographies. The taxonomic position was organized according to Wynne (2011). In the studied area the Dictyotales were represented by 20 taxa, distributed among the genera Canistrocarpus (three), Dictyopteris (five), Dictyota (six), Lobophora (one), Padina (four) and Spatoglossum (one). Five species are being cited as the first occurrence to Alagoas´ coast (C. crispatus (J.V. Lamour.) De Paula & De Clerck, D. jamaicensis W.R. Taylor, D. polypodioides (A.P.D.E. Candolle) J.V.Lamouroux, D. pinnatifida Kützing and P. antillarum (Kützing) Piccone). The study provides identification key to the species level and for each species identified a description, comments and ecological illustration. Among the 20 species of Dictyotales found, only Canistrocarpus cervicornis, C. crispastus, Dictyopteris delicatula, Dictyota jamaicensis, Padina antillarum and Spatoglossum schroederi occurred in the four sampling stations. The greatest richness was found in rocky substratum with occurrence of all species. Of the 20 taxa, 19 were common in both the seasons. Regarding the frequency of occurrence, in the dry and rainy season two taxa occurred as very common C. cervicornis and Dictyopteris delicatula. The similarity analysis (ANOSIM) showed significant differences between the sampling sites. The genera that had some problems in their identification were mostly Canistrocarpus and Dictyota, but with the observation of morphological and anatomical characters, conflicts were resolved. Chemical and biomolecular analyzes should be undertaken to better define the taxonomic limits of conflicting species of these genera.