The State of Maranhão comprises the second largest coastline in Brazil. Nonetheless, few floristic surveys on restinga vegetation have been performed in Northeastern Brazil. This study aimed to survey floristic in a restinga of Maranhão, and to assess its similarity to other restingas in the states of Pará and Piauí. Botanical specimens were sampled at Sítio Aguahy, in the municipality of São José de Ribamar, along the eastern coast of Maranhão between June/2012 and October/2013. Species identification and life forms classification followed the usual methods employed in floristic studies. Similarities in plant composition of six sites were estimated based on cluster analysis through Bray-Curtis distance. In the studied area, we found 116 phanerogamic species, 100 genera and 52 families; 19 species were new occurrences for the restinga of Maranhão. Families with largest number of species were Fabaceae, Cyperaceae, Rubiaceae, Poaceae, Myrtaceae, Asteraceae, Malvaceae, Combretaceae, and Eriocaulaceae, which comprised 49.2% of all sampled species. We identified 41 nanophanerophytes, 34 terophytes, 15 camephytes, ten microphanerophytes, six hemicryptophytes, and five lianas. Similarity analyses indicated greater affinity between the restinga flora from the states of Maranhão and Pará than that observed for the states of Maranhão and Piauí, suggesting that the process of species colonization in the former is more likely derived from the Amazon Forest. It is expected that these results may encourage future researchers to conduct further surveys in restinga areas of the Maranhão aiming to better understand the influence of neighboring vegetation on the colonization of the coastal areas of Maranhão. KEYWORDS: Coastal sand plains, ecotone, floristic similarity, Brazilian northeast. Riqueza de espécies em uma restinga no leste do Maranhão, Nordeste do Brasil RESUMOO Estado do Maranhão possui o segundo maior litoral da costa brasileira. No entanto, poucos levantamentos florísticos foram realizados nas áreas de restinga no Nordeste do Brasil. O presente estudo teve como objetivo realizar um levantamento florístico em uma área de restinga no Maranhão e analisar a similaridade com a flora das restingas dos Estados do Pará e do Piauí. As coletas botânicas foram realizadas na restinga do Sítio Aguahy, município de São José de Ribamar, na porção oriental da Ilha do Maranhão, no período de junho de 2012 a outubro de 2013. A identificação das espécies e a classificação das formas de vida seguiu a metodologia usual em estudos florísticos. A similaridade foi realizada através de análise de cluster a partir da distância de Bray-Curtis, onde foram considerados seis estudos. Foram listadas 116 espécies fanerogâmicas, 100 gêneros e 52 famílias. Deste total, 19 espécies são apresentadas como novas ocorrências para o litoral do Maranhão. As famílias com maior número de espécies foram Fabaceae, Cyperaceae, Rubiaceae, Poaceae, Myrtaceae, Asteraceae, Malvaceae, Combretaceae e Eriocaulaceae, correspondendo a 49.2% das espécies encontra...

Introduction: The “restingas” (coast vegetation) can serve as a species corridor in ecotonal environments due to the particulars regarding the composition of the flora. The studies covering the entire length of the Maranhão state coast are necessary to understand the diversity and distribution of plant species present in the “restingas”. Objective: The objective of this study was to characterize the structure and conservation of the woody vegetation of a “restinga” in Maranhão. Methods: Phytosociological sampling of woody vegetation was carried out using the quadrants method, followed by classification of species by successional group; in addition to analyzing the diametric and hypsometric data of the populations whose species presented the highest importance value (IV). Results: In total, 24 species and 16 families were identified, 72 % of which were classified in the initial stages of succession. The values of H' and J' were 2.637 nat.ind-1and 0.830, respectively. The mean height and diameter were 2.1 m and 27.66 cm, respectively. The species Coccoloba ramosissima Wedd., Byrsonima crassifolia (L.) Kunth, Anacardium occidentale L., Manilkara triflora (Allemão) Monach, and Astrocaryum vulgare Mart. presented the highest IVs. Conclusions: It was observed that characteristics such as size, power of regrowth, and ease of regeneration processes could be useful for choosing target species for recovery actions in coastal areas.