RESUMO

Assessing genetic diversity within species is key for conservation strategies in the context of human-induced biotic changes. This is important in marine systems, where many species remain undescribed while being overfished, and conflicts between resource-users and conservation agencies are common. Combining niche modelling with population genomics can contribute to resolving those conflicts by identifying management units and understanding how past climatic cycles resulted in current patterns of genetic diversity. We addressed these issues on an undescribed but already overexploited species of sardine of the genus Harengula. We find that the species distribution is determined by salinity and depth, with a continuous distribution along the Brazilian mainland and two disconnected oceanic archipelagos. Genomic data indicate that such biogeographic barriers are associated with two divergent intraspecific lineages. Changes in habitat availability during the last glacial cycle led to different demographic histories among stocks. One coastal population experienced a 3.6-fold expansion, whereas an island-associated population contracted 3-fold, relative to the size of the ancestral population. Our results indicate that the island population should be managed separately from the coastal population, and that a Marine Protected Area covering part of the island population distribution can support the viability of this lineage.

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RESUMO

The recently described Lutz's stingray Hypanus berthalutzae is endemic to the Brazilian Province, including oceanic islands. Although it is expected to have life-history traits similar to the southern stingray H. americanus, little is known about its reproductive biology. Here we present the first observations of courtship behaviour (n = 4), copulation (n = 3) and an induced parturition of H. berthalutzae at the Fernando de Noronha Archipelago, an insular Marine Protected Area from the Equatorial Atlantic Ocean. The mating event records included (1) 'chasing/close following', (2) 'biting/precopulatory biting', (3) 'insertion/copulation' and (4) 'separation'. These results are especially relevant considering that records of reproductive behaviour in the wild are rare for elasmobranchs in general. Mating events occurred in different months, suggesting that the reproductive cycle of H. berthalutzae in this insular system is asynchronous, as observed for other stingray species in regions with favourable environmental conditions and abundant food throughout the year. The opportunistic documentation of the induced parturition allowed for direct nonlethal observation of the two pups at or near full term in late May. Although preliminary, these observations should be considered in future management plans as they provide relevant data about the life-history traits and mating behaviour of this endemic and threatened species.

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Recifes rasos são comumente submetidos à pressões antrópicas, devido à fácil acessibilidade. O objetivo deste estudo foi comparar a diversidade, a estrutura da comunidade e a organização trófica em três setores de recifes de corais em Barra de Tabatinga, Nísia Floresta, Rio Grande do Norte entre dezembro de 2011 e março de 2012. Além disso, verificou-se a influência de variáveis ambientais sobre aqueles parâmetros utilizando métodos de censo visual. Foram encontrados 47 espécies de peixes associados aos recifes. A maioria das espécies consumiu invertebrados, padrão já observado para o Nordeste do Brasil. O índice de Shannon do Setor 1 foi diferente dos demais, o que pode estar relacionado ao grau de conectividade durante a maré seca e a proximidade com um manguezal. Por fim, não houve diferenças significativas entre as comunidades de peixes dos setores, o que sugere que a área parece ser uma única unidade. Contudo, pequenas diferenças na composição e abundância de peixes nos setores elevam a diversidade do local. Dessa forma, todos os setores contribuem para a manutenção e a conservação da área. Estes resultados podem ser úteis para futuros estudos de zoneamento e monitoramento.

Shallow reefs are usually under heavy anthropogenic pressure, due to the easy of accessibility. The aim of this study was to compare the diversity, community structure, and trophic organization in three sectors of shallow reefs in Barra de Tabatinga, Nísia Floresta, Rio Grande do Norte, Northeastern Brazil from December 2011 to March 2012. We also evaluated the influence of environmental variables on those parameters using a visual census. We found 47 reef fish species. Most of the species fed on invertebrates, a similar pattern observed in other regions of Northeastern Brazil. The Shannon index of Sector 1 was different from the others, which could be due to the degree of connectivity with its surroundings during low tide and the proximity with a mangrove. Additionally, there were no significant differences in fish communities between sectors, suggesting that the area seems to function as a single community. However, it is important to highlight that even small differences in the composition and abundance of fish increase the diversity of the area. Thus, all sectors are important to the conservation of the area. Our results could be useful for future work on zoning and monitoring.

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