Abstract
Understanding the connections between sea turtle populations is fundamental for their effective conservation. Brazil hosts important hawksbill feeding areas, but few studies have focused on how they connect with nesting populations in the Atlantic. Here, we (1) characterized mitochondrial DNA control region haplotypes of immature hawksbills feeding along the coast of Brazil (five areas ranging from equatorial to temperate latitudes, 157 skin samples), (2) analyzed genetic structure among Atlantic hawksbill feeding populations, and (3) inferred natal origins of hawksbills in Brazilian waters using genetic, oceanographic, and population size information. We report ten haplotypes for the sampled Brazilian sites, most of which were previously observed at other Atlantic feeding grounds and rookeries. Genetic profiles of Brazilian feeding areas were significantly different from those in other regions (Caribbean and Africa), and a significant structure was observed between Brazilian feeding grounds grouped into areas influenced by the South Equatorial/North Brazil Current and those influenced by the Brazil Current. Our genetic analysis estimates that the studied Brazilian feeding aggregations are mostly composed of animals originating from the domestic rookeries Bahia and Pipa, but some contributions from African and Caribbean rookeries were also observed. Oceanographic data corroborated the local origins, but showed higher connection with West Africa and none with the Caribbean. High correlation was observed between origins estimated through genetics/rookery size and oceanographic/rookery size data, demonstrating that ocean currents and population sizes influence haplotype distribution of Brazil's hawksbill populations. The information presented here highlights the importance of national conservation strategies and international cooperation for the recovery of endangered hawksbill turtle populations.
Highlights
After hatching, sea turtles often present an epipelagic stage characterized by wide dispersal, many times over national boundaries and even oceans [1]
It is usually accepted that these movements are influenced by ocean currents: dispersal at the initial epipelagic phase is thought to be mainly shaped by currents due to the low swimming capability of hatchlings [1,10]; as animals grow and attain more autonomous movement, it is believed that the influence of currents on migrations weakens, but still occurs [11]
Mean haplotype diversity of feeding areas in Brazil was 0.413, which is higher than the mean diversity of the two described feeding grounds off West Africa (h = 0.335), but lower than the diversity of ten populations in the Caribbean (h = 0.647)
Summary
Sea turtles often present an epipelagic stage characterized by wide dispersal, many times over national boundaries and even oceans [1] This stage is generally followed by recruitment to coastal areas with adequate conditions for feeding, resting and development [2]. Understanding how populations connect and how animals disperse from rookeries to feeding areas is a challenging task, but is essential for setting priorities and defining management strategies for conservation [3]. In this context, molecular genetic data have been fundamental in obtaining relevant information on interpopulational connectivity, migrations and natal origins of marine turtle feeding populations [4,5,6,7]. Multidisciplinary approaches using oceanographic and genetic information are being increasingly applied to studies of the dispersal and migration patterns of sea turtles (e.g. [7,13,14,15])
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