Nuclear and mitochondrial DNA reveals isolation of imperilled grey nurse shark populations (Carcharias taurus)

Loss of sharks and other upper-trophic marine predators has sparked worldwide concern for the stability of ocean ecosystems. The grey nurse (ragged-tooth or sand tiger) shark ( Carcharias taurus ) is Vulnerable on a global scale, Critically Endangered in Australia and presumed extinct in parts of its historical range. We used 193 muscle and fin samples collected from six extant populations to assess global mtDNA and microsatellite diversity and the degree of global population genetic structure. Control region mtDNA diversity was low in every population, and two populations (eastern Australia and Japan) contained only a single mtDNA haplotype. Genetic signatures of recent losses of genetic variation were not yet apparent at microsatellite loci, indicating that this low mtDNA variation is not a result of anthropogenic population declines. Population differentiation was substantial between each population pair except Brazil and South Africa, F _ST values ranged from 0.050 to 0.699 and 0.100 to 1.00 for microsatellite and mitochondrial data respectively. Bayesian analysis clearly partitioned individuals into five of the populations from which they were sampled. Our data imply a low frequency of immigrant exchange among each of these regions and we suggest that each be recognized as a distinct evolutionary significant unit. In contrast to pelagic species such as whale shark and white shark that may cross ocean basins and where cooperative international efforts are necessary for conservation, grey nurse shark, like many coastal species, need to be managed regionally.     

Genetic structure of populations of whale sharks among ocean basins and evidence for their historic rise and recent decline

This study presents genetic evidence that whale sharks, Rhincodon typus, are comprised of at least two populations that rarely mix and is the first to document a population expansion. Relatively high genetic structure is found when comparing sharks from the Gulf of Mexico with sharks from the Indo‐Pacific. If mixing occurs between the Indian and Atlantic Oceans, it is not sufficient to counter genetic drift. This suggests whale sharks are not all part of a single global metapopulation. The significant population expansion we found was indicated by both microsatellite and mitochondrial DNA. The expansion may have happened during the Holocene, when tropical species could expand their range due to sea‐level rise, eliminating dispersal barriers and increasing plankton productivity. However, the historic trend of population increase may have reversed recently. Declines in genetic diversity are found for 6 consecutive years at Ningaloo Reef in Australia. The declines in genetic diversity being seen now in Australia may be due to commercial‐scale harvesting of whale sharks and collision with boats in past decades in other countries in the Indo‐Pacific. The study findings have implications for models of population connectivity for whale sharks and advocate for continued focus on effective protection of the world's largest fish at multiple spatial scales.     

Genetic diversity of Chinese water deer (Hydropotes inermis inermis): implications for conservation

The Chinese water deer (Hydropotes inermis inermis) is endemic to China. Historically, the species was widely distributed, but now, habitat loss and poaching have reduced its range and number drastically. In order to provide useful information for its conservation, we have investigated the genetic diversity and population structure of the Chinese water deer by analyzing the 403 bp fragment of the mitochondrial DNA (mtDNA) control region (D-loop). Eighteen different haplotypes were detected in 40 samples. Overall, Chinese water deer have a relatively high-genetic diversity compared to other rare cervid species, with a haplotype diversity of 0.923+/-0.025 and nucleotide diversity of 1.318 +/- 0.146%. No obvious phylogenetic structure among haplotypes was found for samples of different origin. An analysis of molecular variance (AMOVA) showed significant differentiation between the Zhoushan and the mainland population (F(ST)= 0.088, P < 0.001; Phi( ST ) = 0.075, P = 0.043), which suggests that exchanges of individuals between Zhoushan and the mainland should be avoided. We also recommend that a breeding center be set up for the mainland population.     

Effects of the Pleistocene on the mitochondrial population genetic structure and demographic history of the silky shark (<Emphasis Type="Italic">Carcharhinus falciformis</Emphasis>) in the western Atlantic Ocean

The silky shark, Carcharhinus falciformis, is a large-bodied, oceanic-coastal, epipelagic species found worldwide in tropical and subtropical waters. Despite its commercial importance, concerns about overexploitation, and likely ecological significance of this shark as an upper trophic-level predator, understanding of its population dynamics remains unclear for large parts of its distribution. We investigated the genetic diversity, population structure and demographic history of the silky shark along the western Atlantic Ocean based on the use of 707 bp of the mitochondrial DNA control region (mtCR). A total of 211 silky sharks were sampled, originating from five areas along the western Atlantic Ocean. The mitochondrial sequences revealed 40 haplotypes, with overall haplotype and nucleotide diversities of 0.88 (± 0.012) and 0.005 (± 0.003), respectively. The overall population structure was significantly different among the five western Atlantic Ocean regions. Phylogenetic analysis of mtCR sequences from globally sourced silky shark samples revealed two lineages, comprising a western Atlantic lineage and western Atlantic—Indo-Pacific lineage that diverged during the Pleistocene Epoch. In general, tests for the demographic history of silky sharks supported a population expansion for both the global sample set and the two lineages. Although our results showed that silky sharks have high genetic diversity, the current high level of overexploitation of this species requires long-term, scientifically informed management efforts. We recommend that fishery management and conservation plans be done separately for the two western Atlantic matrilineal populations revealed here.     

Mitochondrial DNA diversity and population structure among southern right whales (Eubalaena australis)

The population structure and mitochondrial (mt) DNA diversity of southern right whales (Eubalaena australis) are described from 146 individuals sampled on 4 winter calving grounds (Argentina, South Africa, Western Australia, and the New Zealand sub-Antarctic) and 2 summer feeding grounds (South Georgia and south of Western Australia). Based on a consensus region of 275 base pairs of the mtDNA control region, 37 variable sites defined 37 unique haplotypes, of which only one was shared between regional samples of the Indo-Pacific and South Atlantic Oceans. Phylogenetic reconstruction of the southern right whale haplotypes revealed 2 distinct clades that differed significantly in frequencies between oceans. An analysis of molecular variance confirmed significant overall differentiation among the 4 calving grounds at both the haplotype and the nucleotype levels (F(ST) = 0.159; Phi(ST) = 0.238; P < 0.001). Haplotype diversity was significantly lower in the Indo-Pacific (h = 0.701 +/- 0.037) compared with the South Atlantic (h = 0.948 +/- 0.013), despite a longer history of exploitation and larger catches in the South Atlantic. In fact, the haplotype diversity in the Indo-Pacific basin was similar to that of the North Atlantic right whale that currently numbers about 300 animals. Multidimensional scaling of genetic differentiation suggests that gene flow occurred primarily between adjacent calving grounds within an ocean basin, with mixing of lineages from different calving grounds occurring on feeding grounds.     

Genetic diversity and population structure of wintering Western Sandpipers from the Sinaloa coast,Mexico

ABSTRACT Although Western Sandpipers (Calidris mauri) are one of the best‐studied shorebirds along the Pacific Flyway, their genetic identity and population structure is poorly known. We studied the genetic population structure of nonbreeding Western Sandpipers at Bahia Santa María in Sinaloa, northwestern Mexico. A 685‐bp fragment of the mtDNA control region was sequenced for 162 individuals, resulting in 29 variable positions that defined 41 haplotypes. The most common haplotype (WESA01) occurred in 44% of all individuals, whereas 15 were unique to single individuals. Nucleotide diversity was low (π= 0.0030 ± 0.0019 [SE]), but haplotype diversity was moderately high (h= 0.802 ± 0.033 [SE]). The main two maternal lineages exhibited a slightly different local scale distribution that appeared to be related to migratory chronology. Lineage A represented 71% of the haplotypes and was evenly distributed across the nonbreeding season and habitat types, whereas Lineage B represented only 29% of the haplotypes and was disproportionately represented in January in some habitat types. Overall, the low level of nucleotide diversity, the star‐shape of the haplotype tree, the mismatch distribution, and the significantly negative Tajima's D values suggest that Western Sandpipers underwent a recent demographic expansion. Although our results are based on a small sample size from one of several wintering sites along the Pacific Flyway, Santa María likely contains a relatively high proportion of the species genetic variability because it is the wintering ground of nearly 10% of the global population.     

Movement Patterns of Juvenile Whale Sharks Tagged at an Aggregation Site in the Red Sea

Conservation efforts aimed at the whale shark, Rhincodon typus, remain limited by a lack of basic information on most aspects of its ecology, including global population structure, population sizes and movement patterns. Here we report on the movements of 47 Red Sea whale sharks fitted with three types of satellite transmitting tags from 2009–2011. Most of these sharks were tagged at a single aggregation site near Al-Lith, on the central coast of the Saudi Arabian Red Sea. Individuals encountered at this site were all juveniles based on size estimates ranging from 2.5–7 m total length with a sex ratio of approximately 1∶1. All other known aggregation sites for juvenile whale sharks are dominated by males. Results from tagging efforts showed that most individuals remained in the southern Red Sea and that some sharks returned to the same location in subsequent years. Diving data were recorded by 37 tags, revealing frequent deep dives to at least 500 m and as deep as 1360 m. The unique temperature-depth profiles of the Red Sea confirmed that several whale sharks moved out of the Red Sea while tagged. The wide-ranging horizontal movements of these individuals highlight the need for multinational, cooperative efforts to conserve R. typus populations in the Red Sea and Indian Ocean.     

Isolation and genetic diversity of endangered grey nurse shark (Carcharias taurus) populations

Anthropogenic impacts are believed to be the primary threats to the eastern Australian population of grey nurse sharks (Carcharias taurus), which is listed as critically endangered, and the most threatened population globally. Analyses of 235 polymorphic amplified fragment length polymorphisms (AFLP) loci and 700 base pairs of mitochondrial DNA control region provide the first account of genetic variation and geographical partitioning (east and west coasts of Australia, South Africa) in C. taurus. Assignment tests, analysis of relatedness and Fst values all indicate that the Australian populations are isolated from South Africa, with negligible migration between the east and west Australian coasts. There are significant differences in levels of genetic variation among regions. Australian C. taurus, particularly the eastern population, has significantly less AFLP variation than the other sampling localities. Further, the eastern Australian sharks possess only a single mitochondrial haplotype, also suggesting a small number of founding individuals. Therefore, historical, rather than anthropogenic processes most likely account for their depauperate genetic variation. These findings have implications for the viability of the eastern Australian population of grey nurse sharks.     

Phylogeographic structure suggests multiple glacial refugia in northern Victoria Land for the endemic Antarctic springtail Desoria klovstadi (Collembola, Isotomidae)

We carried out a phylogeographic study using mtDNA (COII) for the endemic springtail Desoria klovstadi (formerly Isotoma klovstadi ) from northern Victoria Land, Antarctica. Low levels of sequence divergence (≤ 1.6%) across 26 unique haplotypes (from 69 individuals) were distributed according to geographic location. Cape Hallett and Daniell Peninsula contained the highest nucleotide (both > 0.004) and haplotype (both > 0.9) diversity with 10 (of 16) and 8 (of 12) unique haplotypes, respectively. All other populations (Football Saddle, Crater Cirque, Cape Jones) had lower diversity with 2–4 unique haplotypes. Across the 69 individuals from five populations there was only a single haplotype shared between two populations (Daniell Peninsula and Football Saddle). Furthermore, nested clade analyses revealed that some of the Daniell Peninsula haplotypes were more closely related to Football Saddle haplotypes than to any other population. Such discrete haplotype groupings suggest historical (rare) dispersal across the Pleistocene (1.8 mya−11 kya) and Holocene (11 kya–present), coupled with repeated extinction, range contraction and expansion events, and/or incomplete sampling across the species range. The nested clade analyses reveal that a common pattern of climatic and geological history over long-term glacial habitat fragmentation has determined the geographic and haplotype distributions found for D. klovstadi .     

The genetic structure of the Lithuanian wolf population

Lithuanian wolves form part of the larger Baltic population, the distribution of which is continuous across the region. In this paper, we evaluate the genetic diversity of the Lithuanian wolf population using mitochondrial DNA analysis and 29 autosomal microsatellite loci. Analysis of the mtDNA control region (647 bp) revealed 5 haplotypes distributed among 29 individuals and high haplotype diversity (0.658). Two haplotypes were distributed across the country, whilst the others were restricted to eastern Lithuania. Analysis of microsatellites revealed high heterozygosity (H_E=0.709) and no evidence for a recent bottleneck. Using detection of first generation migrants, four individuals appeared to assign better with populations genetically differentiated from those resident in Lithuania. These immigrants were males carrying rare mitochondrial haplotypes and were encountered in the eastern part of the country, this indicates that Lithuania is subject to immigration from differentiated populations. Additionally, we did not detect any signs of recent hybridisation with dogs.     

Historical DNA reveals the phylogenetic position of the extinct Alpine lynx

During the last two centuries, lynx populations have undergone severe declines and extinctions in Europe. The Alpine lynx, once distributed across the whole Alpine arc, became extinct due to direct human prosecution and deprivation of its main prey in the 1930s. Similar to the Iberian lynx Lynx pardinus , its taxonomy has been subject to several controversies. Moreover, knowing the taxonomic status of the Alpine lynx will help to define conservation units of extant lynx populations in Europe. In this study, we investigated two mitochondrial DNA regions in museum specimens ( n =15) representing the autochthonous Alpine population and in samples from extant Eurasian lynx Lynx lynx populations in Europe and Asia ( n =17). Phylogenetic analysis (cytochrome b , 345 bp) placed the Alpine lynx within the Eurasian lynx lineage. Among all individuals examined, seven different haplotypes (control region, 300 bp) were observed but no unique Alpine haplotype was discovered. Haplotypes of the extinct Alpine population were identical to previously described haplotypes in Scandinavian lynx signifying a recent genetic ancestry with current European populations. Moreover, our genetic data suggest two distinct glacial refugia for the Carpathian and Balkan population. Overall this study demonstrates that historical DNA from extinct populations can help to disentangle the phylogenetic relationships and historical biogeography of taxa with only a limited number of extant populations remaining.     

An extensive analysis of Y-chromosomal microsatellite haplotypes in globally dispersed human populations

The genetic variance at seven Y-chromosomal microsatellite loci (or short tandem repeats [STRs]) was studied among 986 male individuals from 20 globally dispersed human populations. A total of 598 different haplotypes were observed, of which 437 (73.1%) were each found in a single male only. Population-specific haplotype-diversity values were.86-.99. Analyses of haplotype diversity and population-specific haplotypes revealed marked population-structure differences between more-isolated indigenous populations (e.g., Central African Pygmies or Greenland Inuit) and more-admixed populations (e.g., Europeans or Surinamese). Furthermore, male individuals from isolated indigenous populations shared haplotypes mainly with male individuals from their own population. By analysis of molecular variance, we found that 76.8% of the total genetic variance present among these male individuals could be attributed to genetic differences between male individuals who were members of the same population. Haplotype sharing between populations, phi(ST) statistics, and phylogenetic analysis identified close genetic affinities among European populations and among New Guinean populations. Our data illustrate that Y-chromosomal STR haplotypes are an ideal tool for the study of the genetic affinities between groups of male subjects and for detection of population structure.     

Genetic diversity in endangered Notopterygium forbesii Boissieu based on intraspecies sequence variation of chloroplast DNA and implications for conservation

A thorough understanding of the levels and partitioning of genetic variation across populations and geographical regions of endangered species is a prerequisite to ensure effective conservation and/or restoration activities. Here, we examined chloroplast DNA (cpDNA) trnH-psbA intergenic spacer sequences variation within Notopterygium forbesii, an endangered and endemic perennial herb in China. Sequence data obtained from 141 individuals in 14 populations revealed twenty-two haplotypes. A high level of haplotype diversity (Hd = 0.81) and low level of nucleotide diversity (Pi = 0.0047) were detected. Low genetic differentiation among populations and also among regions was consistently indicated by both hierarchical analyses of molecular variance (AMOVA) and the structure of a neighbor-joining tree. Low level of population differentiation between populations or between regions in cpDNA sequences may be due to effects of the abundance of ancestral haplotype sharing and the high number of private haplotypes fixed for each population. Based on our results, we proposed some conservation strategies.     

Divergence in the chloroplast genome and nuclear rDNA of the rare western australian plant lambertia orbifolia gardner (Proteaceae)

The population genetic structure of the Australian plant Lambertia orbifolia was investigated for chloroplast DNA (cpDNA) and rDNA based on restriction fragment length polymorphism. Variation was assessed in 14-20 individuals from six populations with probes covering the majority of the chloroplast genome and the whole rRNA gene unit. For cpDNA, eight mutations were detected which were distributed over five haplotypes. Nucleotide diversity in the species was high and the majority of this diversity was distributed between populations with diversity within populations restricted to a single population. There was significant differentiation between the two regions in the species distribution with the Narrikup region being distinguished by a single haplotype that was characterized by six unique mutations. Variation in rDNA was detected with three gene length variants present in most individuals. However, the Narrikup region was characterized by homogenization of the gene unit to a single length variant in all individuals. The divergence of the Narrikup region suggests that the disjunction in the species distribution has been present for a long time and the two regions represent separate evolutionary lineages.     

Oceanic dispersal in a sedentary reef shark (Triaenodon obesus): genetic evidence for extensive connectivity without a pelagic larval stage

Aim Most reef fishes are site‐attached, but can maintain a broad distribution through their highly dispersive larval stage. The whitetip reef shark (Triaenodon obesus) is site‐attached, yet maintains the largest Indo‐Pacific distribution of any reef shark while lacking the larval stage of bony (teleost) fishes. Here we use mitochondrial DNA (mtDNA) sequence data to evaluate the enigma of the sedentary reef shark that maintains a distribution across two‐thirds of the planet. Location Tropical Pacific and Indian Oceans. Methods We analysed 1025 base pairs of the mtDNA control region in 310 individuals from 25 locations across the Indian and Pacific Oceans. Phylogeographic and population genetic analyses were used to reveal the dispersal and recent evolutionary history of the species. Results We resolved 15 mtDNA control region haplotypes, but two comprised 87% of the specimens and were detected at nearly every location. Similar to other sharks, genetic diversity was low (h = 0.550 ± 0.0254 and π = 0.00213 ± 0.00131). Spatial analyses of genetic variation demonstrated strong isolation across the Indo‐Pacific Barrier and between western and central Pacific locations. Pairwise Φ_ST comparisons indicated high connectivity among archipelagos of the central Pacific but isolation across short distances of contiguous habitat (Great Barrier Reef) and intermittent habitat (Hawaiian Archipelago). In the eastern Pacific only a single haplotype (the most common one in the central Pacific) was observed, indicating recent dispersal (or colonization) across the East Pacific Barrier. Main conclusions The shallow haplotype network indicates recent expansion of modern populations within the last half million years from a common ancestor. Based on the distribution of mtDNA diversity, this began with an Indo‐West Pacific centre of origin, with subsequent dispersal to the Central Pacific and East Pacific. Genetic differences between Indian and Pacific Ocean populations are consistent with Pleistocene closures of the Indo‐Pacific Barrier associated with glacial cycles. Pairwise population comparisons reveal weak but significant isolation by distance, and notably do not indicate the high coastal connectivity observed in other shark species. The finding of population structure among semi‐contiguous habitats, but population connectivity among archipelagos, may indicate a previously unsuspected oceanic dispersal behaviour in whitetip reef sharks.     

Matriarchal genetic population structure of North American beluga whales Delphinapterus leucas (Cetacea: Monodontidae)

The North American beluga whale Delphinapterus leucas population has been divided into a number of putative geographical stocks based upon migration routes and areas of summer concentration. Nucleotide sequences of the mitochondrial DNA (mtDNA) control region were used to assess whether these geographical stocks are genetically distinct. Beluga whale samples from 25 sites were collected primarily from aboriginal subsistence hunts across North America from 1984 to 1994. Thirty-nine mtDNA haplotypes were identified in 628 beluga samples. No differences were found in the distribution of haplotypes between male and female beluga whales at any sampling site. These haplotypes segregated into two distinct assemblages in both a haplotype network and a neighbour-joining tree. The haplotype assemblages had a geographically disjunct distribution that suggests postglacial recolonization of the North American Arctic from two different refugia.
An analysis of molecular variance based on haplotype relationships and frequency indicated genetic heterogeneity among beluga whale summering groups ( P ≤ 0.001). Sequence divergence estimates between sampling sites also indicated geographical differentiation, particularly between samples taken at east Hudson Bay or St Lawrence River and the western or central Arctic. The results of this study show a high degree of philopatry to specific summering areas by this highly mobile animal.     

Ensemble modeling of the potential distribution of the whale shark in the Atlantic Ocean

The whale shark (Rhincodon typus) is an endangered marine fish species which can be adversely affected by the fishing activities of the industrial purse seine fleet targeting tropical tuna. Tuna tend to aggregate around all types of floating objects, including whale sharks. We analyzed and modeled the spatial distribution and environmental preferences of whale sharks based on the presence and absence data from fishing observations in the Atlantic Ocean. We used a thorough multialgorithm analysis, based on a new presence–absence dataset, and endeavored to follow the most recent recommendations on best practices in species distribution modeling. First, we selected a subset of relevant variables using a generalized linear model that addressed multicollinearity, statistical errors, and information criteria. We then used the selected variables to build a model ensemble including 19 different algorithms. After eliminating models with insufficient performance, we assessed the potential distribution of whale sharks using the mean of the predictions of the selected models. We also assessed the variance among the predictions of different algorithms, in order to identify areas with the highest model consensus. The results show that several coastal regions and warm shallow currents, such as the Gulf Stream and the Canary and Benguela currents, are the most suitable areas for whale sharks under current environmental conditions. Future environmental projections for the Atlantic Ocean suggest that some of the suitable regions will shift northward, but current concentration areas will continue to be suitable for whale shark, although with less productivity, which could have negative consequences for conservation of the species. We discuss the implications of these predictions for the conservation and management of this charismatic marine species.     

Chloroplast DNA phylogeography of the endangered Japanese red maple (Acer pycnanthum): the spatial configuration of wetlands shapes genetic diversity

Aim Japanese red maple (Acer pycnanthum K. Koch) is an endangered species which grows in discrete wetland ecosystems within a limited geographical range. It is an important relic of geologic time, an endemic of unique wetland ecosystems and an indicator of hotspots of plant species diversity. However, information on its genetic characteristics across its range is lacking. Our aim was to determine the genetic structure and diversity of the species and make recommendations for conservation. Location Wetlands in central Honshu Island, Japan. Methods We collected leaf samples from 400 individuals of A. pycnanthum in 30 populations, extracted total DNA from each and sequenced three non‐coding regions of chloroplast DNA. Results We identified nine haplotypes. High haplotype diversity (0.81) and the occurrence of rare haplotypes in eight distant populations suggest that wetlands provided multiple, adequate‐size refuges during the Last Glacial Maximum. We found only one to four haplotypes within populations. The high degree of differentiation (G_ST = 0.83) implies that gene flow by seeds among populations is restricted. Eight populations demonstrated a positive contribution to the total genetic diversity owing to occurrence of rare and private haplotypes. Such populations are concentrated in the south‐western part of the species distribution. According to the spatial autocorrelation analysis, there were significant spatial clusters of populations, which were characterized by similar haplotype composition. Using the haplotype distribution, samova and barrier detected nearly identical genetic boundaries. Main conclusion In spite of the species’ limited geographical range, we identified a relatively high number of haplotypes and a clear geographical structure. We propose six management units, which can be used for future conservation activities, such as introduction of new individuals for on‐site conservation projects and seed collection for ex situ conservation.     

Horizontal Movements,Migration Patterns,and Population Structure of Whale Sharks in the Gulf of Mexico and Northwestern Caribbean Sea

Whale sharks, Rhincodon typus, aggregate by the hundreds in a summer feeding area off the northeastern Yucatan Peninsula, Mexico, where the Gulf of Mexico meets the Caribbean Sea. The aggregation remains in the nutrient-rich waters off Isla Holbox, Isla Contoy and Isla Mujeres, Quintana Roo for several months in the summer and then dissipates between August and October. Little has been known about where these sharks come from or migrate to after they disperse. From 2003–2012, we used conventional visual tags, photo-identification, and satellite tags to characterize the basic population structure and large-scale horizontal movements of whale sharks that come to this feeding area off Mexico. The aggregation comprised sharks ranging 2.5–10.0 m in total length and included juveniles, subadults, and adults of both sexes, with a male-biased sex ratio (72%). Individual sharks remained in the area for an estimated mean duration of 24–33 days with maximum residency up to about 6 months as determined by photo-identification. After leaving the feeding area the sharks showed horizontal movements in multiple directions throughout the Gulf of Mexico basin, the northwestern Caribbean Sea, and the Straits of Florida. Returns of individual sharks to the Quintana Roo feeding area in subsequent years were common, with some animals returning for six consecutive years. One female shark with an estimated total length of 7.5 m moved at least 7,213 km in 150 days, traveling through the northern Caribbean Sea and across the equator to the South Atlantic Ocean where her satellite tag popped up near the Mid-Atlantic Ridge. We hypothesize this journey to the open waters of the Mid-Atlantic was for reproductive purposes but alternative explanations are considered. The broad movements of whale sharks across multiple political boundaries corroborates genetics data supporting gene flow between geographically distinct areas and underscores the need for management and conservation strategies for this species on a global scale.     

An unprecedented aggregation of whale sharks, Rhincodon typus, in Mexican coastal waters of the Caribbean Sea

Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of whale sharks (dubbed "the Afuera") that occurs east of the tip of the Yucatán Peninsula in the Caribbean Sea. The 2009 Afuera event comprised the largest aggregation of whale sharks ever reported, with up to 420 whale sharks observed in a single aerial survey, all gathered in an elliptical patch of ocean approximately 18 km(2). Plankton studies indicated that the sharks were feeding on dense homogenous patches of fish eggs, which DNA barcoding analysis identified as belonging to little tunny, Euthynnus alletteratus. This contrasts with the annual Cabo Catoche aggregation nearby, where prey consists mostly of copepods and sergestid shrimp. Increased sightings at the Afuera coincide with decreased sightings at Cabo Catoche, and both groups have the same sex ratio, implying that the same animals are likely involved in both aggregations; tagging data support this idea. With two whale shark aggregation areas, high coastal productivity and a previously-unknown scombrid spawning ground, the northeastern Yucatán marine region is a critical habitat that deserves more concerted conservation efforts.