Diversity and community composition of marine mollusks fauna on a mainland island of the coast of Paraná, southern Brazil

A Ilha do Farol e uma ilha continental, no estado do Parana, sul do Brasil. Devido a sua posicao em relacao ao continente, tres ambientes distintos sao observados nela: area de costao rochoso exposto ao mar aberto (A); area estuarina (B); area de praia arenosa (C). Considerando que as ilhas continentais sao excelentes modelos de estudo que reproduzem as condicoes ambientais da zona costeira em menor escala, o estudo teve como objetivo levantar e pesquisar a malacofauna marinha na Ilha do Farol e comparar sua diversidade e composicao. O metodo de amostragem foi baseado em coletas mensais nos tres ambientes da ilha durante dois anos (2011-2012). O levantamento encontrou 91 especies: 47 Gastropoda, 41 Bivalvia e tres Scaphopoda. A maior riqueza e abundância de especies prevaleceu no ambiente A. A maior equidade foi observada em B e o maior dominio em C. Houve predominância de Gastropoda e Bivalvia em A, enquanto a frequencia de Scaphopoda nao variou entre os ambientes. A composicao de especies das tres classes variou entre as tres areas. A variacao da diversidade e composicao das especies nos tres ambientes podem estar relacionados com as caracteristicas naturais de cada ambiente da ilha, como salinidade e acao de ondas. Palavras chave : Abundância, conservacao, equitabililidade, levantamento, riqueza, Mollusca. Abstract : Farol Island is a continental island in the state of Parana, southern Brazil. Due to its position in relation to the continent, three distinct environmental areas are observed: rocky shore area with open exposure to the sea (A) estuarine area (B); sandy beach area (C). Considering that the continental islands are excellent study models that reproduce the environmental conditions of the coastal zone in a smaller scale, the study aimed at surveying and researching the marine malacofauna on the Farol Island and comparing the diversity and shellfish composition. The sampling method was based on a monthly collection in three locations for two years (2011-2012). The survey found 91 species: 47 Gastropoda, 41 Bivalvia and three Scaphopoda. The highest abundance and species richness prevailed in environmental area A. The greatest equitability was observed in B and the highest dominance in C. There was a predominance of Gastropoda and Bivalvia in A, while the frequency of Scaphopoda did not vary among environments. The species composition of the three classes varied among the three areas. The variation of diversity and species composition in the three environments may be related to the natural characteristics of each side of the island, as salinity and wave action. Key words : Abundance, conservation, equitability, survey, richness, Mollusca.