Turtle groups or turtle soup: dispersal patterns of hawksbill turtles in the Caribbean

Abstract

Despite intense interest in conservation of marine turtles, spatial ecology during the oceanic juvenile phase remains relatively unknown. Here, we used mixed stock analysis and examination of oceanic drift to elucidate movements of hawksbill turtles (Eretmochelys imbricata) and address management implications within the Caribbean. Among samples collected from 92 neritic juvenile hawksbills in the Cayman Islands we detected 11 mtDNA control region haplotypes. To estimate contributions to the aggregation, we performed 'many-to-many' mixed stock analysis, incorporating published hawksbill genetic and population data. The Cayman Islands aggregation represents a diverse mixed stock: potentially contributing source rookeries spanned the Caribbean basin, delineating a scale of recruitment of 200-2500 km. As hawksbills undergo an extended phase of oceanic dispersal, ocean currents may drive patterns of genetic diversity observed on foraging aggregations. Therefore, using high-resolution Aviso ocean current data, we modelled movement of particles representing passively drifting oceanic juvenile hawksbills. Putative distribution patterns varied markedly by origin: particles from many rookeries were broadly distributed across the region, while others would appear to become entrained in local gyres. Overall, we detected a significant correlation between genetic profiles of foraging aggregations and patterns of particle distribution produced by a hatchling drift model (Mantel test, r = 0.77, P < 0.001; linear regression, r = 0.83, P < 0.001). Our results indicate that although there is a high degree of mixing across the Caribbean (a 'turtle soup'), current patterns play a substantial role in determining genetic structure of foraging aggregations (forming turtle groups). Thus, for marine turtles and other widely distributed marine species, integration of genetic and oceanographic data may enhance understanding of population connectivity and management requirements.

Finding the ‘lost years’ in green turtles: insights from ocean circulation models and genetic analysis

“…Because the source location of all particles is known in our rspb.royalsocietypublishing.org Proc R Soc B 280: 20131468 simulations, a single value is produced for each rookery and FG, whereas MSA generates a probability with a mean and 95% CI. We used the mean MSA estimate, as is conventional in similar studies [16]. We did not 'correct' the particle tracking estimates to reflect the fewer sites available in MSA, because our goal was to compare the techniques with their full suite of strengths and limitations.…”

“…Confidence intervals (CIs) for MSA estimates are typically wide owing to inherent limitations: some locations are unavailable for sampling and there are often broadly shared haplotypes among rookeries [6,13]. Thus, considering population connectivity based on physical transport processes is probably necessary to help guide MSA interpretation [12,[14][15][16][17]. Here, the combination of oceanic dispersal simulations and genetic MSA estimates offer a substantive hypothesis regarding basin-wide population connectivity and provide unprecedented information on the distribution of young turtles during their 'lost years'.…”

A Piece of a Puzzle of Haplotypes for the Indian Ocean Hawksbill Turtle

“…This means that on those sites a prevalent maternal inherited structure of the nesting populations and their hatchlings exists and prevails for long periods of time (if the rookery does not become extinct) [19]. The number and variety of haplotypes exhibited by a rookery is its "banner" [21].…”

“…Haplotypes work as "genetic tags" [21], especially in what concerns the definition of nesting populations as management units (MUs) [1] [19]. Genetic tags can be used to understand how diversified a rookery is, and to what extent it is important to manage the area around it [21].…”

“…Genetic tags can be used to understand how diversified a rookery is, and to what extent it is important to manage the area around it [21]. …”