Conservation implications of complex population structure: lessons from the loggerhead turtle (Caretta caretta)

Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1346, Kaneohe, HI 96744, USA.
Molecular Ecology (Impact Factor: 5.84). 08/2005; 14(8):2389-402. DOI: 10.1111/j.1365-294X.2005.02598.x
Source: PubMed

ABSTRACT Complex population structure can result from either sex-biased gene flow or population overlap during migrations. Loggerhead turtles (Caretta caretta) have both traits, providing an instructive case history for wildlife management. Based on surveys of maternally inherited mtDNA, pelagic post-hatchlings show no population structure across the northern Atlantic (phi(ST) < 0.001, P = 0.919), subadults in coastal habitat show low structure among locations (phi(ST) = 0.01, P < 0.005), and nesting colonies along the southeastern coast of the United States have strong structure (phi(ST) = 0.42, P < 0.001). Thus the level of population structure increases through progressive life history stages. In contrast, a survey of biparentally inherited microsatellite DNA shows no significant population structure: R(ST) < 0.001; F(ST) = 0.002 (P > 0.05) across the same nesting colonies. These results indicate that loggerhead females home faithfully to their natal nesting colony, but males provide an avenue of gene flow between regional nesting colonies, probably via opportunistic mating in migratory corridors. As a result, all breeding populations in the southeastern United States have similar levels of microsatellite diversity (H(E) = 0.70-0.89), whereas mtDNA haplotype diversity varies dramatically (h = 0.00-0.66). Under a conventional interpretation of the nuclear DNA data, the entire southeastern United States would be regarded as a single management unit, yet the mtDNA data indicate multiple isolated populations. This complex population structure mandates a different management strategy at each life stage. Perturbations to pelagic juveniles will have a diffuse impact on Atlantic nesting colonies, mortality of subadults will have a more focused impact on nearby breeding populations, and disturbances to adults will have pinpoint impact on corresponding breeding populations. These findings demonstrate that surveys of multiple life stages are desirable to resolve management units in migratory marine species.

Download full-text


Available from: Robert John Toonen, Jul 01, 2015
1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sea turtles perform extensive migratory movements between feeding, developmental and nesting areas. Developmental areas for immature loggerheads turtles (Caretta caretta) are usually composed of individuals from multiple distant rookeries. Thus, impacts on such stocks usually affect multiple colonies, which require international efforts for conservation. This study describes the molecular genetic composition of the more austral foraging and developmental grounds of loggerhead sea turtles in the Atlantic Ocean and infers the possible origin and dispersal patterns of the species. Analyses were performed using shorter (380 bp) and larger (760 bp) sequences of the control region of mitochondrial DNA (mtDNA) from 24 samples of bycatch and 37 samples of stranded loggerhead sea turtles on the coast of the province of Buenos Aires, Argentina. All specimens (N = 61) were adults and sub-adults (mean ± standard deviation curved carapace length CCL = 68.3 ± 13.4 cm; range: 52.0 to 107.0 cm, N = 41 individuals measured). Both shorter and longer mtDNA sequence analysis showed that in the foraging grounds of the Argentinean coast only haplotypes from Brazilian nesting areas (CC-A4 = 98% and CC-A24 = 2% for shorter sequences, and CC A4.2 = 81%, CC A4.1 = 17% and CC A24.1 = 2% for longer sequences) were found. The homogeneous stock located relatively close to the rookery where individuals originated contradicts the paradigm of immature loggerhead sea turtles forming mixed stocks in foraging and developmental areas. The conservation of the stock in coastal areas of Argentina could benefit the nesting population in the nearby Brazilian rookeries, and could be achieved by conservation actions between these two countries, as well as Uruguay in between.
    Journal of Experimental Marine Biology and Ecology 05/2015; 466:85-91. DOI:10.1016/j.jembe.2015.02.006 · 2.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the at-sea spatial behaviour of sea turtles is a priority for their conservation. In the present paper, the current information on the distribution and movement patterns of the two species breeding in the Mediterranean, the loggerhead and the green turtle, is reviewed, focusing mainly on the 195 published routes of satellite-tracked turtles. A satisfactory level of knowledge about adults' migrations and other movements is reached only for loggerheads breeding at Zakynthos Island, Greece, and for green and loggerhead females nesting in Cyprus, while studies at foraging grounds are limited to logger-heads in the western and central parts of the basin. Adult males and females mostly show quite uniform post-breeding migratory patterns, typically moving towards individually specific neritic foraging grounds. A much higher variability is shown by loggerhead juveniles, which is probably associated with differences in their spatial behaviour while in oceanic or neritic waters. Evidence of seasonal migrations driven by lower temperatures in winter is available only for adult and juvenile loggerheads frequenting the two northernmost parts of the basin, i.e. the Ligurian and the northern Adriatic Sea. Current knowledge gaps and priorities for further research in the Mediterranean are discussed.
    Italian Journal of Zoology 10/2014; 81(4). DOI:10.1080/11250003.2014.963714 · 0.87 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In migratory species female- and male-mediated gene flow are important for defining relevant Management Units, and for evaluating connectivity between these and their respective foraging grounds.The stock composition at five Mediterranean foraging areas was investigated by analysing variation in the mitochondrial D-loop and six microsatellite loci in a sample of 268 loggerhead turtles (Caretta caretta) stranded or accidentally caught by fisheries. This involved a comprehensive Mixed Stock Analysis which considers also recent data from major rookeries in Libya and Turkey, and the generation of a standardized nomenclature of allele sizes at the microsatellite loci.The results indicate: that the north Adriatic, the Tunisian continental shelf, the waters around Malta and the Italian Ionian Sea represent important areas for the conservation of rookeries in Greece, Libya and Turkey, respectively;that waters off the Italian peninsula and the islands of Lampedusa and Malta are mainly inhabited by individuals of Mediterranean origin, with a major contribution from the nearest and largest colonies, while Atlantic turtles are restricted to the western areas;that specific migratory routes exist from rookeries to foraging grounds;a poor bi-parental genetic structuring, which suggests a high male-mediated gene flow in the Mediterranean;mixing of small turtles in waters distant from natal rookeries, and recovery of structuring for large-sized individuals; andthat uncommon mtDNA haplotypes are more powerful markers than microsatellite alleles in assessing an individual's origin, owing to their higher geographic specificity. Copyright © 2013 John Wiley & Sons, Ltd.
    Aquatic Conservation Marine and Freshwater Ecosystems 12/2013; 23(6). DOI:10.1002/aqc.2338 · 1.76 Impact Factor