Article

Low genetic diversity after a bottleneck in a population of a critically endangered migratory marine turtle species

Authors:
  • Zayed University / UAE Dolphin Project
  • Elasmo Project
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Abstract

Hawksbill turtles (Eretmochelys imbricata), which are distributed throughout the world's oceans, have undergone drastic declines across their range, largely due to anthropogenic factors. Assessing sizes, genetic variability and structure of their populations at global and regional levels is critical to the development of conservation manage- ment strategies. Here, nuclear and mitochondrial markers were used to analyse patterns of parentage and pop- ulation structure in hawksbill turtles in United Arab Emirates (UAE) waters, utilizing samples from two life stages (hatchlings and juveniles), and to compare the UAE population with neighboring populations. Weak genetic dif- ferentiation was detected between juveniles and hatchlings and between the nesting sites of Dubai and Sir Bu Nair. Parentage analysis suggested that only 53 females and 74–80 males contributed to the hatchlings from 67 nests across three nesting sites in UAE (Dubai, Sir Bu Nair, Abu Dhabi). No females were identified as nesting in more than one location. In Dubai and Abu Dhabi, single paternity was the norm (75%), whereas on Sir Bu Nair, multiple paternity was detected in the majority of nests (67%). Polygyny was also frequently detected on Sir Bu Nair (15% of the overall number of males), but not in the other nesting sites. Comparison of the UAE population with published data from other populations suggests that population structure exists both within the Gulf and between the Gulf and Indian Ocean populations, and that the UAE population has lower genetic variability than the Seychelles population. Finally, the data suggest that the UAE population, and the Gulf population overall, experienced a bottleneck/founder event. The observed overall low genetic variability, evidence of population structure in the Gulf, and strong differentiation between the Gulf and the Indian Ocean populations, raises con- cerns about the sustainability of this species in this near-enclosed basin. These results highlight the need for re- gional collaboration in the development of management measures for the long-term conservation of this Critically Endangered species.

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... While many injuries from anthropogenic origins can threaten individual sea turtles, rehabilitation can often save injured animals that would otherwise die; for example, entanglement in discarded monofilament line and fishing nets can cause serious wounds and amputations that can lead to death without treatment [4]. Furthermore, individual rescue and rehabilitation can be particularly important within small, threatened populations, such as hawksbill turtles Eretmochelys imbricata (Linnaeus 1766) in the Arabian Gulf region, which have low contemporary breeding numbers and low genetic variability [9]. In fact, the northwest Indian Ocean has been highlighted as a 'High Risk, High Threat' Regional Management Unit for hawksbill and olive ridley Lepidochelys olivacea (Eschscholtz 1829) turtles, as well as an area with critical data shortages [10], making it an ideal location to develop and implement rehabilitation programs. ...
... This study demonstrates that sea turtles continue to face many anthropogenic threats in Gulf waters even though most Gulf countries have laws in place to protect them. There are relatively small nesting populations of green and hawksbill turtles throughout the Gulf [9,13,25,38] but, to the authors knowledge there are no reports of nesting activity by loggerhead turtles in the Gulf. Since its inception in 2004, the DTRP has treated and released over 1800 sea turtles that are likely to have died without human intervention (DTRP, unpublished data). ...
... Since its inception in 2004, the DTRP has treated and released over 1800 sea turtles that are likely to have died without human intervention (DTRP, unpublished data). Most of these sea turtles were juvenile hawksbills, a species that has low genetic variability in Gulf populations when compared with Indian Ocean populations, with an estimated 53 female hawksbills that contributed to hatchlings from three key nesting sites in the UAE [9]. We therefore believe that this rehabilitation program has been a positive and significant contribution to help support this regional sea turtle population. ...
Article
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... Phylogeographic studies of hawksbill turtles have been performed apart for populations in Brazil (Lara-Ruiz et al., 2006;Vilaça et al., 2013;Proietti et al., 2014), Caribbean (Bass et al., 1996;Troëng et al., 2005;Bowen and Karl, 2007;Velez-Zuazo et al., 2008;Blumenthal et al., 2009;Richardson et al., 2009;Browne et al., 2010;LeRoux et al., 2012;Carreras et al., 2013;Wood et al., 2013;Gorham et al., 2014;Trujillo-Arias et al., 2014;Cazabon-Mannette et al., 2016;Hill et al., 2018;Labastida-Estrada et al., 2018), Eastern Atlantic (Monzón-Argüello et al., 2010Putman et al., 2014), Indo-Pacific , Persian Gulf (Tabib et al., 2011(Tabib et al., , 2014Natoli et al., 2017), Eastern Pacific (Gaos et al., 2012(Gaos et al., , 2016(Gaos et al., , 2017(Gaos et al., , 2018Zuniga-Marroquin and Monteros, 2017), Southeast Asia (Nishizawa et al., 2016) and Japan (Nishizawa et al., 2010). The first genetic studies used mtDNA control region data based on approximately 300 bp sequences (Bass et al., 1999;Dias-Fernández et al., 1999;Troëng et al., 2005;Bowen and Karl, 2007;Nishizawa et al., 2010). ...
... Populations of the Indian Ocean were clustered in two groups: Persian Gulf and Seychelles-Chagos, which present strong genetic differentiation with high numbers of exclusive haplotypes (11 and 13, respectively). Natoli et al. (2017) suggest that the Persian Gulf population originated from a single founder event, followed by population expansion. ...
... Haplotypes EiIP106 and EiIP108 were described as unique to the rookeries in mangrove estuaries, a particular hawksbill's behavior found in Pacific Central America (Gaos et al., 2017). Nevertheless, Natoli et al. (2017) reported haplotype EiUAE08 in the United Arab Emirates, which matches with the haplotype EiIP106 based on the 739 bp sequence. The duplicity in the haplotype names precluded the detection of a possible origin of the Eastern Pacific haplotype, conducting to uncertain conclu- 6 Arantes et al. sions of species dynamics. ...
Article
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The hawksbill turtle is a broadly distributed, highly migratory and critically endangered sea turtle species. The paucity of studies restricts the comprehension of its behavior and life history. In this work, we performed a global phylogeographic analysis using a compilation of previously published mitochondrial haplotype data to understand the dynamics and diversity of hawksbill populations worldwide. Our results revealed a complex demographic pattern associated to hawksbill phylogeography since the Pliocene. Isolation by distance is not enough to explain distinct demographic units of hawksbill turtles, which are also influenced by other factors as oceanic currents, coral reef distribution and nesting timing. The foraging aggregations are typically mixed stocks of individuals originating from multiple nesting areas, but there is also a trend of foragers coming from nearby natal beaches. Phylogenetic analysis indicates two highly divergent major lineages split between Atlantic and Indo-Pacific rookeries, but there is also a more recent Atlantic Ocean colonization from the Indo-Pacific Ocean. Long-distance dispersal events are likely responsible for homogenization between distant populations within oceans. Our findings provided new insights about population connectivity, identified gaps that should be prioritized in future research and highlighted the need for international efforts aiming at hawksbill's conservation.
... This strategy may confer selective advantages, such as fertility assurance, heightened offspring viability, and increased genetic diversity (Chapman et al., 2009;Phillips et al., 2017). In contrast, polygyny, or males mating with multiple females, has rarely been reported for marine turtles (but see Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017), despite the existence of > 30 studies that have assayed > 1000 maternal families (see Tedeschi et al., 2015;Lee et al., 2018). ...
... This study provides the first insights into hawksbill mating systems in the eastern Pacific Ocean. We found polygynous mating strategies are common at Bahía de Jiquilisco and detected the highest levels of polygyny (approximately 32% for known males) reported to date for a marine turtle population (Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017). We attribute the prevalence of this mating strategy to a limited number of males in the reproductive population (Phillips et al., 2013(Phillips et al., , 2014a(Phillips et al., , 2014b. ...
... We found evidence of polygyny for approximately 32% of known male hawksbills that sired nests at Bahía de Jiquilisco during the 2015 nesting season. To our knowledge, these are the highest levels of polygyny reported to date for any marine turtle species (Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017). Although polygyny has been documented in various mammals, birds and reptiles (Moore et al., 2008;Stiver et al., 2008;Pérez-González et al., 2009;Bro-Jørgensen, 2014), it is a phenomenon that has rarely been detected in marine turtles, despite > 30 genetic studies investigating polygamy in the taxon (Tedeschi et al., 2015;Lee et al., 2018). ...
Article
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Genetic analyses of nuclear DNA (e.g., microsatellites) are a primary tool for investigating mating systems in reptiles, particularly marine turtles. Whereas studies over the past two decades have demonstrated that polyandry (i.e., females mating with multiple males) is common in marine turtles, polygyny (i.e., males mating with multiple females) has rarely been reported. In this study we investigated the mating structure of Critically Endangered hawksbill turtles (Eretmochelys imbricata) at Bahía de Jiquilisco in El Salvador, one of the largest rookeries in the eastern Pacific Ocean. We collected genetic samples from 34 nesting females and hatchlings from 41 clutches during the 2015 nesting season, including one nest from each of 27 females and two nests from seven additional females. Using six highly polymorphic microsatellite loci, we reconstructed the paternal genotypes for 22 known male turtles and discovered that seven (31.8%) sired nests from multiple females, which represents the highest polygyny level reported to date for marine turtles and suggests that this is a common mating structure for this population. We also detected multiple paternity in four (11.8%) clutches from the 34 females analyzed, confirming polyandrous mating strategies are also employed. The high level of polygyny we documented suggests there may be a limited number of sexually mature males at Bahía de Jiquilisco; a scenario supported by multiple lines of empirical evidence. Our findings highlight key management uncertainties, including whether polygynous mating strategies can compensate for potential ongoing feminization and the low number of adult males found for this and possibly other marine turtle populations.
... This strategy may confer selective advantages, such as fertility assurance, heightened offspring viability, and increased genetic di- versity ( Chapman et al., 2009;Phillips et al., 2017). In contrast, poly- gyny, or males mating with multiple females, has rarely been reported for marine turtles (but see Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017), despite the existence of > 30 studies that have assayed > 1000 maternal families (see Tedeschi et al., 2015;Lee et al., 2018). ...
... This study provides the first insights into hawksbill mating systems in the eastern Pacific Ocean. We found polygynous mating strategies are common at Bahía de Jiquilisco and detected the highest levels of polygyny (approximately 32% for known males) reported to date for a marine turtle population ( Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017). We attribute the prevalence of this mating strategy to a limited number of males in the reproductive population (Phillips et al., 2013(Phillips et al., , 2014a(Phillips et al., , 2014b). ...
... We found evidence of polygyny for approximately 32% of known male hawksbills that sired nests at Bahía de Jiquilisco during the 2015 nesting season. To our knowledge, these are the highest levels of polygyny reported to date for any marine turtle species (Crim et al., 2002;Stewart and Dutton, 2014;Natoli et al., 2017). Although poly- gyny has been documented in various mammals, birds and reptiles ( Moore et al., 2008;Stiver et al., 2008;Pérez-González et al., 2009;BroJørgensen, 2014), it is a phenomenon that has rarely been detected in marine turtles, despite > 30 genetic studies investigating polygamy in the taxon ( Tedeschi et al., 2015;Lee et al., 2018). ...
... This is in contrast to green (Chelonia mydas), loggerhead (Caretta caretta), and olive ridley (Lepidochelys olivacea) turtles tracked in the region, the majority of which do move between foraging and nesting habitat in the Gulf, Arabian Sea, and elsewhere in the northern Indian Ocean (Rees et al. 2010(Rees et al. , 2012a(Rees et al. , 2012bMobaraki et al. 2020;Pilcher et al. 2020Pilcher et al. , 2021. Hawksbill turtles nesting in the Gulf may be restricted to its waters through a) adaptation; b) physical limitations and the inability to navigate the currents that the other, larger species of sea turtles can transit to move between the Gulf and northern Indian Ocean (as occurs in immature loggerhead turtles in the Mediterranean Sea; Carreras et al. 2006); or c) a bottleneck/founder event (see Natoli et al. 2017;Arantes et al. 2020) that other sea turtles nesting in the Gulf and foraging outside the Gulf did not experience (Jensen et al. 2019) resulting in different postnesting migratory behavior/s. The narrow Strait of Hormuz renders the Gulf a semienclosed sea, with extreme thermal variability and high salinity (Vaughan et al. 2019). ...
... Relationships between size and genetic characteristics are impossible to assess given that global studies of hawksbill turtles include samples from populations in the Gulf (Vargas et al. 2016;Reid et al. 2019) but not the Red Sea or Arabian Sea. The Gulf hawksbill turtle population is considered to have originated from a single founder event and subsequent population expansion (Natoli et al. 2017) so a genetic relationship seems unlikely, but a comparative study of wider populations in the northern Indian Ocean could aid understanding of factors resulting in smaller turtle size and consequent clutch count. ...
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This study presents the first published data on the morphometrics of nesting hawksbill turtles (Eretmochelys imbricata) and their eggs and counts of yolked and yolkless eggs per clutch from Iranian Islands in the northern Persian Gulf. We found significant variation in some variables among 4 main nesting islands (e.g., weight of yolked eggs, p = 0.000; number of yolkless eggs per clutch, p = 0.017), but effect size was moderate or less (r < 0.5 or d < 0.8). The diameter (p = 0.039), weight (p = 0.028), and number of yolked eggs (p = 0.000) per clutch increased significantly with curved carapace length (CCL), but the effect size was only large for the number of yolked eggs (f² = 0.152). The number of yolkless eggs did not vary with CCL (p = 0.453) or with the number of yolked eggs (p = 0.523). A meta-analysis of global hawksbill turtle morphometrics and reproductive output revealed significant variation in CCL (p = 0.000) and number of yolked eggs (p < 0.001), with nesting region having a very large effect size on both variables (g² = 0.880 and 0.616, respectively). Hawksbill turtles from the Gulf were smaller than populations from the Gulf of Oman (p < 0.001), Arabian Sea (p = 0.000), Caribbean (p = 0.000), West Atlantic (p = 0.000), and Southwest Pacific (p = 0.000) but not the Red Sea (p = 0.104), and laid fewer yolked eggs than populations in the Caribbean (p < 0.001) and West Atlantic (p = 0.001) but not the Red Sea (p = 0.636). This may be due to hawksbill turtles nesting in the Gulf remaining within its waters postnesting so adult body size is restricted by the relatively poor foraging habitat and/or success and/or the extreme environments, subsequently limiting clutch size. More information on home range and foraging habitat is required to draw similar conclusions about hawksbill turtles nesting in the Red Sea. Hawksbill turtles nesting in the Gulf, Red Sea, and Arabian Sea also appear to lay larger number of yolkless eggs per clutch than other populations worldwide (mean = 17.6 ± 10.8 SD [range = 0–59]). The functional role of yolkless eggs, potentially in the maintenance of thermal and hydric conditions within tolerable conditions in shallow nests laid in extreme environments, requires further investigation. Similarly, the potential for yolkless eggs to be an adaptation to extreme nest environments in other sea turtle species also nesting in the northern Indian Ocean also warrants examination.
... Worldwide, the largest sampling gap across sea turtle species is the dispersal stage ( Figure 3). Haplotypes for this life stage are so far only available from the Gulf of Mexico for green turtles (current study, Shamblin, Witherington, et al., 2018), the Gulf of Mexico (current study) and strandings in France (Monzón-Argüello et al., 2012) for loggerheads, and the Gulf of Mexico (current study) and strandings in UAE (Natoli et al., 2017) for hawksbills. Connectivity among life stages is also difficult to characterize in a genetic framework because there are few nucleotide differences between mtDNA haplotypes, both for delineating within-species lineages and among species for which close genetic relationships remain despite deep divergence. ...
... The Atlantic hawksbill clades are also nested within the Indo-Pacific lineages in our gene tree analysis (Figure 3), suggesting a similar diversification pattern in both green turtles and hawksbills (Nishizawa et al., 2010(Nishizawa et al., , 2012van der Zee et al., 2021). Within the mainly Indo-Pacific hawksbill Clade IP-I, the haplotypes EiIP-27, EiIP-33, and EiIP-36 span opposite sides of the Indo-Pacific from Iran, UAE, and Seychelles to the Pacific coast of central America (Gaos et al., 2016(Gaos et al., , 2018(Gaos et al., , 2020LaCasella et al., 2014;Natoli et al., 2017;Tabib et al., 2014;Vargas et al., 2016;Zuñiga-Marroquin & De Los Monteros, 2017 ; Table S10). ...
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Regional genetic differentiation of mitochondrial lineages occurs in migratory species with natal philopatry such as sea turtles. However, early juvenile dispersal represents a key opportunity for gene flow and colonization of new regions through founder events, making it an important yet under-studied life stage. To assess connectivity among sea turtle life stages and ocean basins, we sequenced mitochondrial DNA (mtDNA) fragments from 35 juveniles sampled in the Gulf of Mexico from the rarely observed dispersal stage across three species: green turtles (Chelonia mydas; n = 30), hawksbills (Eretmochelys imbricata; n = 3), and loggerheads (Caretta caretta; n = 2). We estimated green turtle rookery contributions using a many-to-many Bayesian mixed stock analysis that incorporated dispersal probabilities based on rookery size and transport via ocean currents. We assembled a gene tree including 709 distinct mtDNA control region haplotypes from the literature for all seven extant sea turtle species to assess gaps in life-stage data across ocean basins, as well as contextualize the lineages we sampled from dispersing juveniles. Our results indicate a high likelihood that green turtles sampled in the Gulf of Mexico originated from rookeries along the coast of Mexico, with smaller contributions from Costa Rica and Suriname. The gene tree analysis yielded species-level relationships consistent with those presented previously, while intra-species relationships between lineages and ocean basins differed, particularly within loggerhead and green turtle clades. Our results highlight the lack of genetic data from juvenile sea turtles, especially the early dispersal stage, and the potential for these data to answer broader questions of connectivity and diversification across species and lineages.
... The type of mating system employed by a species may differ spatially or temporally (Moore et al. 2009;Natoli et al. 2017;Phillips et al. 2013). Therefore, the genetic mating system described for this C. decresii population may not necessarily be employed throughout the entire season, across years or across all populations. ...
... Population density is likely to influence mateencounter rates and hence rates of multiple paternity. Therefore, spatial or seasonal variation in population density may result in varying rates of multiple paternity (Natoli et al. 2017). The population on which this study is based has a relatively high population density (C. ...
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A clear understanding of population structure is essential for assessing conservation status and implementing management strategies. A small, non-migratory population of humpback whales in the Arabian Sea is classified as “Endangered” on the IUCN Red List of Threatened Species, an assessment constrained by a lack of data, including limited understanding of its relationship to other populations. We analysed 11 microsatellite markers and mitochondrial DNA sequences extracted from 67 Arabian Sea humpback whale tissue samples and compared them to equivalent datasets from the Southern Hemisphere and North Pacific. Results show that the Arabian Sea population is highly distinct; estimates of gene flow and divergence times suggest a Southern Indian Ocean origin but indicate that it has been isolated for approximately 70,000 years, remarkable for a species that is typically highly migratory. Genetic diversity values are significantly lower than those obtained for Southern Hemisphere populations and signatures of ancient and recent genetic bottlenecks were identified. Our findings suggest this is the world's most isolated humpback whale population, which, when combined with low population abundance estimates and anthropogenic threats, raises concern for its survival. We recommend an amendment of the status of the population to “Critically Endangered” on the IUCN Red List.
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Advancements in digital photography have facilitated the use of photo-ID to track individual animals, making this technique of great value for conservation biology. However, the time required to manually match new photographs to those stored in a database is proportional to the size of the database. Therefore, there is need for investigating the potential to automate the searching processes through computerized means. We encountered hawksbill turtles that were members of an ongoing study who had lost flipper tags and shell etchings. To identify individuals, we first manually searched photographs of turtles previously captured and released. Manual visual matching of these turtles (n = 2) resulted in successful matches for 100% of tested photographs. To investigate automated recognition of turtles in a database, we used I3S to digitize scutes on the dorsal and lateral surfaces of the head, and compare spot patterns through the automated system. I3S successfully matched the two return turtles with visual matches. To assess the ability of I3S to identify turtles both present in, and absent from the database, we blind-tested a series of photographs of turtle heads and faces through both manual visual methods and I3S. With I3S, 84.6% of the computerized photos were successfully matched with photos in the database, with scores produced ranging from 0.069 to 0.435. Through this study, we recognized the potential for long-term identification of individual turtles, but that the usefulness of a photo-database depends on the quality of photos taken, and the flexibility of the computer program used.
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We present the first data on hawksbill turtle post-nesting migrations and behaviour in the Arabian region. Tracks from 90 post-nesting turtles (65 in the Gulf and 25 from Oman) revealed that hawksbills in the Arabian region may nest up to 6 times in a season with an average of 3 nests per turtle. Turtles from Qatar, Iran and the UAE generally migrated south and southwest to waters shared by the UAE and Qatar. A smaller number of turtles migrated northward towards Bahrain, Saudi Arabia and one reached Kuwait. Omani turtles migrated south towards Masirah island and to Quwayrah, staying close to the mainland and over the continental shelf. The widespread dispersal of hawksbill foraging grounds across the SW Gulf may limit habitat protection options available to managers, and we suggest these be linked to preservation of shallow water habitats and fishery management. In contrast, the two main foraging areas in Oman were small and could be candidates for protected area consideration. Critical migration bottlenecks were identified at the easternmost point of the Arabian Peninsula as turtles from Daymaniyat Islands migrate southward, and between Qatar and Bahrain. Overall, Gulf turtles spent 68% of the time in foraging ground with home ranges of 40–60 km2 and small core areas of 6 km2. Adult female turtles from Oman were significantly larger than Gulf turtles by ~ 11 cm x¯=81.4CCL and spent 83% of their time foraging in smaller home ranges with even smaller core areas (~ 3 km2), likely due to better habitat quality and food availability. Gulf turtles were among the smallest in the world x¯=70.3CCL and spent an average of 20% of time undertaking summer migration loops, a thermoregulatory response to avoid elevated sea surface temperatures, as the Gulf regularly experiences sustained sea surface temperatures > 30 °C. Fishery bycatch was determined for two of the 90 turtles. These spatio-temporal findings on habitat use will enable risk assessments for turtles in the face of multiple threats including oil and gas industries, urban and industrial development, fishery pressure, and shipping. They also improve our overall understanding of hawksbill habitat use and behaviour in the Arabian region, and will support sea turtle conservation-related policy decision-making at national and regional levels.
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Genetic diversity and phylogeography of Hawksbill sea turtle was studied by using sequencing of the mitochondrial DNA (D-loop and tRNA pro region). 45 dead embryos were collected from the Qeshm (25 samples) and Kish Islands (20 samples) in the Persian Gulf. Analysis of sequence diversity showed over 890 bp of the mtDNA D-loop and tRNA pro region revealed 5 polymorphism sites and 7 haplotypes. Two new haplotypes were submitted on NCBI gene bank as Iran3 with GU997696 accession number and Iran7 with JN627023 accession number. Haplotype (h) and nucleotide (π) diversity was (h= 0.313 and π= 0.0006) for Qeshm Island and (h= 0.111 and π=0.0002) for Kish Island, respectively. Total haplotype diversity was calculated as 0.212, which had demonstrated low genetic diversity in this area. The Fst and P-value showed that Hawksbill turtles of Qeshm and Kish Islands are different populations. A comparison of our data with previous studies showed a relationship between the Persian Gulf and Indo-Pacific Hawksbill turtles and also sharp relationship with east Atlantic. Hawksbill turtles of the Persian Gulf have been migrated from the Pacific and the Oman Sea into this area. As a result, evidence of populations migration was not found from the West.
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The concept of ‘effective population size’ (Ne), which quantifies how quickly a population will lose genetic variability, is one of the most important contributions of theoretical evolutionary biology to practical conservation management. Ne is often much lower than actual population size: how much so depends on key life history and demographic parameters, such as mating systems and population connectivity, that often remain unknown for species of conservation concern. Molecular techniques allow the indirect study of these parameters, as well as the estimation of current and historical Ne. Here, we use genotyping to assess the genetic health of an important population of the critically endangered hawksbill turtle (Eretmochelys imbricata), a slow-to-mature, difficult-to-observe species with a long history of severe overhunting. Our results were surprisingly positive: we found that the study population, located in the Republic of Seychelles, Indian Ocean, has a relatively large Ne, estimated to exceed 1000, and showed no evidence of a recent reduction in Ne (i.e. no genetic bottleneck). Furthermore, molecular inferences suggest the species' mating system is conducive to maintaining a large Ne, with a relatively large and widely distributed male population promoting considerable gene flow amongst nesting sites across the Seychelles area. This may also be reinforced by the movement of females between nesting sites. Our study underlines how molecular techniques can help to inform conservation biology. In this case our results suggest that this important hawksbill population is starting from a relatively strong position as it faces new challenges, such as global climate change.
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This field guide covers the major resource groups likely to be encountered in the fisheries of Kuwait, Eastern Saudi Arabia, Bahrain, Qatar, and the United Arab Emirates. It includes marine plants, shrimps, lobsters, crabs, bivalves, gastropods, cephalopods, sharks, batoid fishes, bony fishes, sea snakes, sea turtles, sea birds, and marine mammals. In order to serve as a tool for ecological and biodiversity studies, all species know from the Gulf of certain groups are included. These include the sharks, batoid fishes, bony fishes, sea turtles, and marine mammals. Each resource group is introduced by a general section on technical terms and measurements pertinent to that group and an illustrated guide to higher taxonomic groups when relevant. Species are then treated in a subsequent guide that includes scientific nomenclature, common English and Arabic names where available, size information, information on habitat, biology, and fisheries, diagnostic features, and one or more illustrations, some of which are included in colour. The guide is fully indexed and a list of references is appended.
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Populations of endangered Caribbean sea turtles are far more depleted than realized because current conservation assessments do not reflect historic nesting data. We used historical sources to analyze changes in the numbers of nesting populations and population sizes for green and hawksbill turtles on all known nesting beaches in the Caribbean over the past millennium. We present the first maps of historic nesting populations, which provide the basis for an objective measure of changes in distribution and abundance. Our results indicate that 20% of historic nesting sites have been lost entirely and 50% of the remaining nesting sites have been reduced to dangerously low populations. Recent conservation efforts have resulted in large population increases at several nesting sites, but loss of widespread nesting throughout the Caribbean and reductions in the Caribbean-wide population since human hunting began indicate that Caribbean turtles are far from recovered. Focusing attention on a small number of nesting populations is a risk-prone strategy; conservation programs should instead broaden their scope to protect both large and small nesting populations throughout the Caribbean.
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The study of turtle population genetics has come a long way in the past few decades. In the early 1990s, technologies such as polymerase chain reaction (PCR) and automated DNA sequencing spearheaded a boom in molecular ecology. Microsatellite and mitochondrial DNA haplotype markers became the methods of choice for many turtle studies. Today, the rate of research continues unabated. The emergence of new methods, approaches and ideas means exciting prospects for the molecular ecology of marine turtles. A review of genetic markers that have been used for turtle research provides a starting point for those breaking into this area for the first time. Here current molecular techniques are discussed, but upcoming new ideas and methods are also highlighted. A recently proposed hypothesis to explain the polyandrous behaviour of female turtles means a fresh direction for multiple paternity studies. A new statistical approach (individual-based analysis) offers future studies analytical methods other than F-statistics, and an alternative means to test male-biased gene flow. Paternity analysis now enables robust reconstruction of male genotypes from their offspring, elucidating the genetics of adult male turtles without collecting them in the field. With whole genome amplification (WGA) limited DNA samples can be amplified for long-term storage, large-scale analyses and easy exchange between laboratories. New genetic markers are essential for future progress, and breakthrough DNA sequencing technologies will facilitate marker discovery. The next-generation sequencing methods also means that the new ‘-omics’ techniques of genomics and transcriptomics may in the future be applicable to marine turtle research.
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Nesting by hawksbill sea turtles Eretmochelys imbricata in Barbados, West Indies, has been monitored since 1992. Data from the index beach indicate that the number of nests may have increased as much as 8-fold over this period. The estimated abundance of nesting females on Barba- dos is 1250, suggesting that this eastern Caribbean island now hosts one of the largest rookeries in the wider Caribbean, with over 230 females nesting on the index beach alone. Given its extreme east- erly position and the prevailing north-westerly current flow into the Caribbean Sea, Barbados is likely to be a significant contributor to foraging grounds throughout the region. Primary females, which are untagged and without tag scars, made up the majority of females encountered on nesting beaches in most years, suggesting that reductions in juvenile and sub-adult mortality, both nationally and regionally, are significant to the increase in number of nesting females. Females nest every 2.47 yr on average, although remigration intervals of individual females vary (range: 1 to 6 yr), sug- gesting environmental influences on nesting periodicity. The average clutch frequency estimated from the index beach was 4.1 nests per female, but that calculated from less intensively surveyed beaches was lower. Primary and Remigrant females differed in length, mass and clutch frequency; the results must be viewed with caution, however, as preliminary laparoscopic examinations re- vealed that some Primary females were not in fact nesting for their first season, and because differ- ences in nest site fidelity between the 2 groups of females could potentially cause the differences in clutch frequencies estimated.
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Productivity in the Arabian Sea is one of the highest in the world. It is controlled by seasonally reversing monsoonal wind-driven upwelling of nutrient-rich deeper waters which fuel phytoplankton growth. The detailed history of upwelling-induced productivity in the eastern Arabian Sea is unknown. Here we present paleoproductivity records from a composite sediment core at the millennial scale during the last 80 kyr B.P. These records are based on relative abundance counts of planktonic foraminifera and organic carbon contents, which are shown to mainly vary in concert. The eastern Arabian Sea upwelling-induced productivity was higher in the glacial period than in the Holocene, but it fell repeatedly on millennial timescales. These productivity declines occurred during cold events in the North Atlantic region, with the most pronounced changes prevailing during the Heinrich events. Hence, seasonal monsoon winds that drive upwelling-induced productivity in the east were weak when the North Atlantic was cold. These weak winds resulted in stratification of the water column, comparable to today's Arabian Sea stratification in the intermonsoonal period. Combining the new eastern with published western Arabian Sea results shows that the entire biological factory was severely diminished during the North Atlantic Heinrich events, and the seasonal productivity change in the Arabian Sea monsoon system was reduced with year-round low productivity.
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Results of hawksbill turtle Eretmochelys imbricata nest monitoring on Cousin Island, Seychelles, indicate an 8-fold increase in abundance of nesting females since the early 1970s when the population was highly depleted. From 1999 to 2009, the population increased at an average rate of 16.5 turtles per season. Females were individually tagged, and nesting data were derived from indirect evidence of nesting attempts (i.e. tracks) and actual turtle sightings (56 to 60% of all encoun- ters). Survey effort varied over the years for a variety of reasons, but the underlying trends over time are considered robust. To overcome biases associated with variable survey effort, we estimated pop- ulation changes by fitting a Poisson distribution to data on numbers of times each individual was seen at this breeding site in a season. This was used to estimate unseen individuals, and hence the total number of nesting females each season. The maximum number of individuals emerging onto Cousin Island to nest within a single season was estimated to be 256 (2007 to 2008) compared to 23 in 1973. Tag returns indicate that many turtles nest on both Cousin and Cousine Islands (2 km apart), and that some inter-island nesting also occurs between Cousin and more remote islands within the Seychelles.
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Patterns of mitochondria] DNA variation were used to determine generic relationship s among hawksbill (Eretmochelys imbricata) and green turtle (Chelonia mydas) populations i n the Chagos Archipelago (Central Indian Ocean) and those in three adjacent localities : th e Republic of Seychelles, the Arabian Peninsula, and western Australia_ Nesting hawksbills i n Seychelles and Chagos are both characterized by high frequency mtDNA variants no t recorded elsewhere in the world and differ from each other by significant haplotype frequenc y shift! . The few nesting green turtles sampled from Chagos had haplotypes shared with gree n turtle populations in both the eastern and western Indian Ocean but distinct from those i n the Arabian Peninsula . Populations of foraging juvenile hawksbill turtles from the Chagos and Seychelles coul d not be genetically differentiated from ea, c -nd their pooled mtDNA frequencies are no t significantly different from either Seycheili or Chagos rookeries, but are more similar t o Seychelles rookeries . Notably, none of the haplotypes observed in western Australian rooker -ies were detected in these foraging populations . These data indicate that Seychelles is a majo r source of juveniles in both Seychelles and Chagos foraging populations but tl possibility o f Arabian Peninsula or other unsampled stocks in the region also making signi i let contribu -tions cannot he precluded . Additional samples from both hawksbill and green tt de rookerie s in the Chagos are needed to elucidate these patterns .
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The hawksbill turtle (Eretmochelys imbricata) is a regular inhabitant of the Arabian Gulf. Sea turtles are included in the IUCN red list, and the hawksbill is listed as critically endangered. From March 2004 to September 2010, the Dubai Turtle Rehabilitation Project received 150 sick and injured juvenile hawksbill turtles, rescued in the Arabian Gulf. Blood samples taken from the animals during convalescence and prior to release were analyzed, establishing a hematology and biochemistry reference interval for clinically healthy rehabilitated juvenile hawksbill turtles from the Arabian Gulf. Hemoglobin, packed cell volume (PCV), white blood cell count (WBC), aspartate aminotransferase (AST), creatine kinase (CK), uric acid, glucose, calcium, phosphorus, total protein, albumin, globulin, potassium, and sodium were evaluated. When compared to values at first presentation, clinically healthy rehabilitated turtles had significantly higher PCV (P = 0.006) and significantly lower WBC (P = 0.0001), heterophils (P = 0.005), monocytes (P = 0.04), AST (P = 0.03), and CK (P = 0.0001). There was no significant change in hemoglobi n, eosinophils, basophils, uric acid, glucose, calcium, phosphorus, total protein, albumin, globulin, potassiu m, or sodium levels between turtles at first presentation and post-rehabilitation.
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The region of the Arabian Marginal Seas and Gulfs (AMSG) continues to be of paramount importance to the world community for a variety of economic and political reasons. The immense petroleum resources and their maritime export from the region and the complex evolution and conflict of competing political entities are constantly demanding attention. In May 1999, over 50 atmospheric and oceanic scientists gathered at the Stennis Space Center to assess their knowledge of this region and identify pathways forward in understanding the physical system regulating these marginal seas and gulfs. Each of the key components of the region is individually important and each presents complex scientific questions unto itself. One of our primary intentions, however, was to seek connectivity across the AMSG region.
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Highly mobile marine species in areas with no obvious geographic barriers are expected to show low levels of genetic differentiation. However, small-scale variation in habitat may lead to resource polymorphisms and drive local differentiation by adaptive divergence. Using nuclear microsatellite genotyping at 20 loci, and mitochondrial control region sequencing, we investigated fine-scale population structuring of inshore bottlenose dolphins (Tursiops aduncus) inhabiting a range of habitats in and around Moreton Bay, Australia. Bayesian structure analysis identified two genetic clusters within Moreton Bay, with evidence of admixture between them (F(ST) = 0.05, P = 0.001). There was only weak isolation by distance but one cluster of dolphins was more likely to be found in shallow southern areas and the other in the deeper waters of the central northern bay. In further analysis removing admixed individuals, southern dolphins appeared genetically restricted with lower levels of variation (AR = 3.252, π = 0.003) and high mean relatedness (r = 0.239) between individuals. In contrast, northern dolphins were more diverse (AR = 4.850, π = 0.009) and were mixing with a group of dolphins outside the bay (microsatellite-based STRUCTURE analysis), which appears to have historically been distinct from the bay dolphins (mtDNA Φ(ST) = 0.272, P < 0.001). This study demonstrates the ability of genetic techniques to expose fine-scale patterns of population structure and explore their origins and mechanisms. A complex variety of inter-related factors including local habitat variation, differential resource use, social behaviour and learning, and anthropogenic disturbances are likely to have played a role in driving fine-scale population structure among bottlenose dolphins in Moreton Bay.
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Mammal species characterized by highly fluc-tuating populations often maintain genetic diversity in response to frequent demographic bottlenecks, suggesting the ameliorating influence of life history and behavioral factors. Immigration in particular is expected to promote genetic recovery and is hypothesized to be the most likely process maintaining genetic diversity in fluctuating mam-mal populations. Most demographic bottlenecks have been inferred retrospectively, and direct analysis of a natural population before, during, and after a bottleneck is rare. Using a continuous 10-year dataset detailing the complete demographic and genetic history of a fluctuating popula-tion of golden-mantled ground squirrels (Spermophilus lateralis), we analyzed the genetic consequences of a 4-year demographic bottleneck that reduced the population to seven adult squirrels, and we evaluated the potential ''rescue effect'' of immigration. Analysis of six microsat-ellite loci revealed that, while a decline in allelic richness was observed during the bottleneck, there was no observed excess of heterozygosity, a characteristic bottleneck sig-nature, and no evidence for heterozygote deficiency during the recovery phase. In addition, we found no evidence for inbreeding depression during or after the bottleneck. By identifying immigrants and analyzing their demographic and genetic contributions, we found that immigration promoted demographic recovery and countered the genetic effects of the bottleneck, especially the loss of allelic richness. Within 3 years both population size and genetic variation had recovered to pre-bottleneck levels, supporting the role of immigration in maintaining genetic variation during bottleneck events in fluctuating populations. Our analyses revealed considerable variation among analytical techniques in their ability to detect genetic bottlenecks, suggesting that caution is warranted when evaluating bot-tleneck events based on one technique.
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We present STRUCTURE HARVESTER (available at http://taylor0.biology.ucla.edu/structureHarvester/), a web-based program for collating results generated by the program STRUCTURE. The program provides a fast way to assess and visualize likelihood values across multiple values of K and hundreds of iterations for easier detection of the number of genetic groups that best fit the data. In addition, STRUCTURE HARVESTER will reformat data for use in downstream programs, such as CLUMPP. KeywordsStructure–Population structure–Population genetics–Evanno method–Visualization–Clustering
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We present the first data collected on the genetic mating system of the hawksbill turtle Eretmochelys imbricata, the only marine turtle not studied to date. We examined paternity within 12 egg clutches from ten female hawksbill turtles from Sabah Turtle Islands, Malaysia. A total of 375 hatchlings were analysed using five microsatellite markers. Results demonstrated that clutches from two out of ten females were sired by multiple males (maximum of two). Although at a low frequency, observation of multiple paternity indicates that hawksbill turtles exhibit the same genetic mating system (polyandry) as observed for other species of marine turtles. Consistent paternity across multiple clutches laid by individual females in one breeding season supports the hypothesis that sperm are stored from mating prior to nesting and are then used to fertilize all subsequent clutches of eggs that season. Keywords Eretmochelys imbricata –Hawksbill turtle–Multiple paternity–Microsatellites–Marine turtles–Endangered species
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Bahia state hosts over 90% of hawksbill (Eretmochelys imbricata) nests registered in the main nesting sites monitored by Projeto Tamar-IBAMA in Brazil. The genetic diversity of this hawksbill population (n=119) was assayed through the analyses of 752bp of the mitochondrial DNA control region in nesting females. Seven distinct haplotypes, defined by 125 polymorphic sites, were found. Most of the individuals (n=67) display four typical hawksbill haplotypes, 50 individuals display two haplotypes characteristic of the loggerhead turtle (Caretta caretta) and two individuals had a haplotype affiliated with the olive ridley (Lepidochelys olivacea). These results demonstrate hybridization between the hawksbills and two species that nest along the Bahia coast. Of special interest is the high occurrence of loggerhead × hawksbill hybrids (42%), which display loggerhead mtDNA haplotypes but are characterized morphologically as hawksbills. The true hawksbill haplotypes present only three variable sites and low genetic diversity values (h=0.358±0.069; π=0.0005±0.0001). The occurrence of several nesting individuals with identical mtDNA from another species may also suggest a long history of introgression between species producing likely F2 or further generation hybrids. Marine turtle hybrids have been previously reported, but the high frequency observed in Bahia is unprecedented. Such introgression may influence evolutionary pathways for all three species, or may introduce novel morphotypes that develop apart from the parental species. The presence of a unique hybrid swarm has profound conservation implications and will significantly influence the development and implementation of appropriate management strategies for these species.
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Several estimators of population differentiation have been proposed in the recent past to deal with various types of genetic markers (i.e., allozymes, nucleotide sequences, restriction fragment length polymorphisms, or microsatellites). We discuss the relationships among these estimators and show how a single analysis of variance framework can accomodate these qualitatively different data types.
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The genetic structure of green turtle (Chelonia mydas) rookeries located around the Australian coast was assessed by (1) comparing the structure found within and among geographic regions, (2) comparing microsatellite loci vs. restriction fragment length polymorphism analyses of anonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic structure was observed over all regions at both sets of nuclear markers, though the microsatellite data provided greater resolution in identifying significant genetic differences in pairwise tests between regions. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter being more congruent with geography. Estimated rates of gene flow were generally higher than expected for nuclear DNA (nDNA) in comparison to mtDNA, and this difference was most pronounced in comparisons between the northern and southern Great Barrier Reef (GBR). The genetic data combined with results from physical tagging studies indicate that the lack of nuclear gene divergence through the GBR is likely due to the migration of sGBR turtles through the courtship area of the nGBR population, rather than male-biased dispersal. This example highlights the value of combining comparative studies of molecular variation with ecological data to infer population processes.
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Episodes of population growth and decline leave characteristic signatures in the distribution of nucleotide (or restriction) site differences between pairs of individuals. These signatures appear in histograms showing the relative frequencies of pairs of individuals who differ by i sites, where i = 0, 1, .... In this distribution an episode of growth generates a wave that travels to the right, traversing 1 unit of the horizontal axis in each 1/2u generations, where u is the mutation rate. The smaller the initial population, the steeper will be the leading face of the wave. The larger the increase in population size, the smaller will be the distribution's vertical intercept. The implications of continued exponential growth are indistinguishable from those of a sudden burst of population growth Bottlenecks in population size also generate waves similar to those produced by a sudden expansion, but with elevated uppertail probabilities. Reductions in population size initially generate L-shaped distributions with high probability of identity, but these converge rapidly to a new equilibrium. In equilibrium populations the theoretical curves are free of waves. However, computer simulations of such populations generate empirical distributions with many peaks and little resemblance to the theory. On the other hand, agreement is better in the transient (nonequilibrium) case, where simulated empirical distributions typically exhibit waves very similar to those predicted by theory. Thus, waves in empirical distributions may be rich in information about the history of population dynamics.
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We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
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The main purposes are to collate information of the region, to review marine systems and processes in the intertidal and shallow sublittoral parts of the Arabian seas, and to highlight human utilisation and environmental consequences. The first section presents the geological, geographical, climatic and oceanographic background to the area. The second section examines what is known of the region's marine communities, interpreting the relationships between the marine systems and physical conditions for: reefs and coral communities; coral reef fish assemblages; other reef components and processes; seaweeds and seasonality; seagrasses and other dynamic substrates; intertidal areas - mangal associated ecosystems, marshes, sabkha and beaches; and the pelagic system. The next section synthesizes and concludes the biogeographical material and interprets the effects of natural stress on the biota. The final section describes and discusses the human use and management of the region, including fisheries. -after Authors
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Information on the genetic structure of marine species is essential for stock improvement programs. In order to analyses the genetic diversity of the Hawksbill turtle (Eretmochelys imbricte) by the microsatellite genetic method, 64 samples were caught from the beaches located in Kish and Qeshm islands. Polymerase chain reactions (PCR) of genomic DNA extracted from the samples were carried out using 5 pairs of microsatellite primers. The results of this study indicated that all 5 pairs of primers were polymorphic. Average numbers of real allele and effective allele were 4.90 and 2.99, respectively. Average rate of observed heterozygosity was 0.570 and that for expected heterozygosity was 0.616. Study of the Hardy-Weinberg equilibrium was shown the entire locus had not equilibrium except Cm3 and Ei8 locus in Kish area. Fst (0.166) and Rst (0.634) calculated by the Analysis of Molecular Variance (AMOVA) test illustrated that there are separate populations of Hawksbill turtle in this part of the Persian Gulf (Kish and Qeshm islands). It seems that Kish's turtles live under better conditions in contrast to their Qeshm counterparts. Diminution of genetic variation within examined population decreases its adaptation to environmental alterations. We identified two different E. imbricte populations from north of the Persian Gulf.
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The overall nesting population of Hawksbill Turtles (Eretmochelys imbricata (Linnaeus, 1766)) on Jarnain and Bu Tinah islands of the United Arab Emirates in the Arabian (Persian) Gulf comprised 48 nests on Jarnain and 17 nests on Bu Tinah. The nesting season was short and extended from mid-March to mid-July, with peak nesting activity in April and May. The average clutch size was 58.6. Both percent hatching success and hatchling size showed a deceasing trend from the beginning to the end of the nesting season. This might be due to the adverse effect of increasing atmospheric temperature from 26 to 48°C and of nest temperature from 26 to 35°C.
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The overexploitation of sharks has become a global environmental issue in need of a comprehensive and multifaceted management response. Tracking studies are beginning to elucidate how shark movements shape the internal dynamics and structure of populations, which determine the most appropriate scale of these management efforts. Tracked sharks frequently either remain in a restricted geographic area for an extended period of time (residency) or return to a previously resided-in area after making long-distance movements (site fidelity). Genetic studies have shown that some individuals of certain species preferentially return to their exact birthplaces (natal philopatry) or birth regions (regional philopatry) for either parturition or mating, even though they make long-distance movements that would allow them to breed elsewhere. More than 80 peer-reviewed articles, constituting the majority of published shark tracking and population genetic studies, provide evidence of at least one of these behaviors in a combined 31 shark species from six of the eight extant orders. Residency, site fidelity, and philopatry can alone or in combination structure many coastal shark populations on finer geographic scales than expected based on their potential for dispersal. This information should therefore be used to scale and inform assessment, management, and conservation activities intended to restore depleted shark populations. Expected final online publication date for the Annual Review of Marine Science Volume 7 is January 03, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Data
1] Productivity in the Arabian Sea is one of the highest in the world. It is controlled by seasonally reversing monsoonal wind‐driven upwelling of nutrient‐rich deeper waters which fuel phytoplankton growth. The detailed history of upwelling‐induced productivity in the eastern Arabian Sea is unknown. Here we present paleoproductivity records from a composite sediment core at the millennial scale during the last 80 kyr B.P. These records are based on relative abundance counts of planktonic foraminifera and organic carbon contents, which are shown to mainly vary in concert. The eastern Arabian Sea upwelling‐ induced productivity was higher in the glacial period than in the Holocene, but it fell repeatedly on millennial timescales. These productivity declines occurred during cold events in the North Atlantic region, with the most pronounced changes prevailing during the Heinrich events. Hence, seasonal monsoon winds that drive upwelling‐induced productivity in the east were weak when the North Atlantic was cold. These weak winds resulted in stratification of the water column, comparable to today's Arabian Sea stratification in the intermonsoonal period. Combining the new eastern with published western Arabian Sea results shows that the entire biological factory was severely diminished during the North Atlantic Heinrich events, and the seasonal productivity change in the Arabian Sea monsoon system was reduced with year‐round low productivity.
Article
Postcopulatory sperm storage can serve a range of functions, including ensuring fertility, allowing delayed fertilization and facilitating sexual selection. Sperm storage is likely to be particularly important in wide-ranging animals with low population densities, but its prevalence and importance in such taxa, and its role in promoting sexual selection, are poorly known. Here, we use a powerful microsatellite array and paternal genotype reconstruction to assess the prevalence of sperm storage and test sexual selection hypotheses of genetic biases to paternity in one such species, the critically endangered hawksbill turtle, Eretmochelys imbricata. In the majority of females (90.7%, N = 43), all offspring were sired by a single male. In the few cases of multiple paternity (9.3%), two males fertilized each female. Importantly, the identity and proportional fertilization success of males were consistent across all sequential nests laid by individual females over the breeding season (up to five nests over 75 days). No males were identified as having fertilized more than one female, suggesting that a large number of males are available to females. No evidence for biases to paternity based on heterozygosity or relatedness was found. These results indicate that female hawksbill turtles are predominantly monogamous within a season, store sperm for the duration of the nesting season and do not re-mate between nests. Furthermore, females do not appear to be using sperm storage to facilitate sexual selection. Consequently, the primary value of storing sperm in marine turtles may be to uncouple mating and fertilization in time and avoid costly re-mating.
Article
Cetaceans are difficult to observe in the wild, and demand complex logistics for dedicated collection of biological data. As such, the distribution of most cetacean species is still poorly understood. Ecological niche models are useful in studying species distributions and their ecological determinants, and platforms of opportunity (e.g. commercial nautical operators) can provide an alternative source for that data in cetaceans. In this study, we modelled common dolphin (Delphinus delphis) habitat preferences using ecological niche modelling and presence data obtained from distinct platforms of opportunity in two different areas in the Portuguese coast (west and south mainland Portugal) for the period 2005-2007. Models from southern Portugal were projected to western Portugal and vice-versa, to check for robustness in predicting the species ecological niche. Our results show that data from platforms of opportunity can result in robust ecological models and provide extremely useful information on cetacean ecology. We found that common dolphins exhibit a patchy distribution pattern over the Portuguese coastline, and identified key habitats for their occurrence. The most important variable associated with this species' distribution was chlorophyll concentration which, given the results from previous research, we hypothesise reflects an ecological specialisation on pelagic schooling fish. Given that the most abundant schooling fish species in Portugal is increasingly overexploited and in constant decline, more attention should be given to the conservation of common dolphin in Portuguese waters.
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Most birds breed in pairs but at least 3% of passerine species are cooperative breeders, whereby more than two adults help to raise the young. The general rarity of cooperative breeding has led to the assumption that cooperative behaviour has evolved from the ancestral trait of pair breeding. However, it has been suggested that pair breeding may be the derived state in some taxa. The primary aim of this research was to test this suggestion using the genus Acanthiza, which contains examples of both cooperatively and pair breeding species. Mitochondrial DNA sequences were used to construct a phylogenetic hypothesis for the tribe containing Acanthiza, the Acanthizini. The breeding behaviour of the species sequenced was determined from records in the literature; where there were no such data the frequency of another social behaviour, flocking, was used as an indicator of breeding behaviour. The mapping of breeding systems onto the phylogeny led to the conclusion that cooperative breeding is the ancestral state in the Acanthizini, with pair breeding evolving twice in the genus Acanthiza. Models explaining the occurrence of cooperative breeding in terms of broad environmental factors or life history do not appear to be applicable to the genus Acanthiza. The pair breeding Acanthiza species cluster into two clades, suggesting some influence of phylogenetic history on the occurrence of the different breeding systems. Combining the results of this study with other data suggests the tendency to breed cooperatively could be ancestral in the superfamily Meliphagoidea.
Article
The identification of population bottlenecks is critical in conservation because populations that have experienced significant reductions in abundance are subject to a variety of genetic and demographic processes that can hasten extinction. Genetic bottleneck tests constitute an appealing and popular approach for determining if a population decline has occurred because they only require sampling at a single point in time, yet reflect demographic history over multiple generations. However, a review of the published literature indicates that, as typically applied, microsatellite-based bottleneck tests often do not detect bottlenecks in vertebrate populations known to have experienced declines. This observation was supported by simulations that revealed that bottleneck tests can have limited statistical power to detect bottlenecks largely as a result of limited sample sizes typically used in published studies. Moreover, commonly assumed values for mutation model parameters do not appear to encompass variation in microsatellite evolution observed in vertebrates and, on average, the proportion of multi-step mutations is underestimated by a factor of approximately two. As a result, bottleneck tests can have a higher probability of 'detecting' bottlenecks in stable populations than expected based on the nominal significance level. We provide recommendations that could add rigor to inferences drawn from future bottleneck tests and highlight new directions for the characterization of demographic history.
Article
For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult.