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1.
The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge
from those nests must swim in opposite directions and search for different surface currents to migrate away from continental
shelf waters. In this laboratory study, we compared the pattern of swimming activity shown by the hatchlings from each coast
over the first 6 days of migration. Turtles from both coasts were equally active during their “frenzy” period (the first 24 h
of swimming) and during the daylight hours of the 5 days that followed (the “postfrenzy” period). However, the west coast
turtles were significantly more active than the east coast turtles during the nocturnal portion of the postfrenzy period.
This difference may be related to the greater distance southwest coast turtles must negotiate to locate surface currents for
transport out of the Gulf of Mexico and into the Atlantic Ocean basin. These differing behavioral strategies may be genetically
determined, as similar correspondence between activity and distance is well known among migratory populations of birds and
fish and is often based upon inherited programs of endogenously driven activity. Alternatively, behavioral differences between
the two nesting groups could be a manifestation of phenotypic plasticity that arises as the hatchlings respond to unique environmental
cues on each coast. 相似文献
2.
The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge from those nests must swim in opposite directions and search for different surface currents to migrate away from continental shelf waters. In this laboratory study, we compared the pattern of swimming activity shown by the hatchlings from each coast over the first 6 days of migration. Turtles from both coasts were equally active during their “frenzy” period (the first 24 h of swimming) and during the daylight hours of the 5 days that followed (the “postfrenzy” period). However, the west coast turtles were significantly more active than the east coast turtles during the nocturnal portion of the postfrenzy period. This difference may be related to the greater distance southwest coast turtles must negotiate to locate surface currents for transport out of the Gulf of Mexico and into the Atlantic Ocean basin. These differing behavioral strategies may be genetically determined, as similar correspondence between activity and distance is well known among migratory populations of birds and fish and is often based upon inherited programs of endogenously driven activity. Alternatively, behavioral differences between the two nesting groups could be a manifestation of phenotypic plasticity that arises as the hatchlings respond to unique environmental cues on each coast. 相似文献
3.
Satellite tracking reveals a dichotomy in migration strategies among juvenile loggerhead turtles in the Northwest Atlantic 总被引:2,自引:2,他引:0
Katherine L. Mansfield Vincent S. Saba John A. Keinath John A. Musick 《Marine Biology》2009,156(12):2555-2570
Few data are available on the movements and behavior of immature Atlantic loggerhead sea turtles (Caretta caretta) from their seasonal neritic foraging grounds within the western north Atlantic. These waters provide developmental habitat
for loggerheads originating from several western Atlantic nesting stocks. We examined the long-term movements of 23 immature
loggerheads (16 wild-caught and seven headstart turtles) characterizing their seasonal distribution, habitat use, site fidelity,
and the oceanographic conditions encountered during their migrations. We identified two movement strategies: (1) a seasonal
shelf-constrained north–south migratory pattern; and (2) a year-round oceanic dispersal strategy where turtles travel in the
Gulf Stream to the North Atlantic and their northern dispersal is limited by the 10–15°C isotherm. When sea surface temperatures
dropped below 20°C, neritic turtles began a migration south of Cape Hatteras, North Carolina (USA) where they established
fidelity to the waters between North Carolina’s Outer Banks and the western edge of the Gulf Stream along outer continental
shelf. Two turtles traveled as far south as Florida. Several turtles returned to their seasonal foraging grounds during subsequent
summers. Northern movements were associated with both increased sea surface temperature (>21°C) and increased primary productivity.
Our results indicate strong seasonal and interannual philopatry to the waters of Virginia (summer foraging habitat) and North
Carolina (winter habitat). We suggest that the waters of Virginia and North Carolina provide important seasonal habitat and
serve as a seasonal migratory pathway for immature loggerhead sea turtles. North Carolina’s Cape Hatteras acts as a seasonal
“migratory bottleneck” for this species; special management consideration should be given to this region. Six turtles spent
time farther from the continental shelf. Three entered the Gulf Stream near Cape Hatteras, traveling in the current to the
northwest Atlantic. Two of these turtles remained within an oceanic habitat from 1 to 3 years and were associated with mesoscale
features and frontal systems. The ability of large benthic subadults to resume an oceanic lifestyle for extended periods indicates
plasticity in habitat use and migratory strategies. Therefore, traditional life history models for loggerhead sea turtles
should be reevaluated. 相似文献
4.
Whilst a range of animals have been shown to respond behaviourally to components of the Earth’s magnetic field, evidence of
the value of this sensory perception for small animals advected by strong flows (wind/ocean currents) is equivocal. We added
geomagnetic directional swimming behaviour for North Atlantic loggerhead turtle hatchlings (Caretta
caretta) into a high-resolution (1/4°) global general circulation ocean model to simulate 2,925-year-long hatchling trajectories
comprising 355,875 locations. A little directional swimming (1–3 h per day) had a major impact on trajectories; simulated
hatchlings travelled further south into warmer water. As a result, thermal elevation of hatchling metabolic rates was estimated
to be between 63.3 and 114.5% after 220 days. We show that even small animals in strong flows can benefit from geomagnetic
orientation and thus the potential implications of directional swimming for other taxa may be broad. 相似文献
5.
Pop-up satellite archival tags were implanted into 68 Atlantic bluefin tuna (Thunnus thynnus Linnaeus), ranging in size from 91 to 295 kg, in the southern Gulf of Maine (n=67) and off the coast of North Carolina (n=1) between July 2002 and January 2003. Individuals tagged in the Gulf of Maine left that area in late fall and overwintered in northern shelf waters, off the coasts of Virginia and North Carolina, or in offshore waters of the northwestern Atlantic Ocean. In spring, the fish moved either northwards towards the Gulf of Maine or offshore. None of the fish crossed the 45°W management line (separating eastern and western management units) and none traveled towards the Gulf of Mexico or the Straits of Florida (known western Atlantic spawning grounds). The greatest depth recorded was 672 m and the fish experienced temperatures ranging from 3.4 to 28.7°C. Swimming depth was significantly correlated with location, season, size class, time of day, and moon phase. There was also evidence of synchronous vertical behavior and changes in depth distribution in relation to oceanographic features.Communicated by J.P. Grassle, New Brunswick 相似文献
6.
Phyllorhiza
punctata, commonly called the Australian white spotted jellyfish, invaded the Caribbean in the 1960s, becoming established there and
subsequently in the United States in the northern Gulf of Mexico (by 2000) and eastern Florida (2001). With the prevailing
Loop Current flowing clockwise around the Gulf of Mexico and joining the Gulf Stream along eastern Florida, potential transport
of P. punctata along the eastern seaboard of the USA could be facilitated. P. punctata medusae were collected in small numbers along the entire Georgia coast during May–November in 2007 and 2008. Medusa bell
diameters increased both years from ca. 10 cm in May to ca. 33 cm in autumn. Specimens lacked zooxanthellae, as reported for
medusae in the northern Gulf of Mexico and Florida. It is possible that the P. punctata medusae observed were transported from established populations to the south; however, whether or not this species is established
along the Georgia coast has yet to be determined. 相似文献
7.
How and when migrants integrate directional information from different sources may depend not only on the bird’s internal
state, including fat stores, but also on the ecological context during passage. We designed experiments to (1) examine the
influence of stored fat on the decision to migrate and on the choice of migratory direction and (2) investigate how the integration
of orientation cue information is tied to energetic status in relation to migration across an ecological barrier. Migratory
orientation of red-eyed vireos (Vireo olivaceus) at twilight was recorded using two different techniques, orientation cage experiments and free-flight release tests, during
both fall and spring migration. During fall migration, the amount of stored fat proved decisive for directional selections
of the vireos. Fat birds chose directions in accordance with migration across the Gulf of Mexico. Lean birds oriented either
parallel to the coast line (cage tests) or moved inland (free-flight releases). Whereas only fat birds showed significant
responses to experimental deflections of the geomagnetic field, lean birds displayed a tendency to shift their activity in
the expected direction, making it difficult to evaluate the prediction that use of the magnetic compass is context dependent.
Fat loads also had a significant effect on the decision to migrate, i.e., fat individuals were more likely to embark on migration
than were lean birds (true for both cage and release experiments). During spring migration, a majority of experimental subjects
were classified as lean, following their arrival after crossing the Gulf of Mexico, and oriented in seasonally appropriate
directions. The vireos also showed significant responses to experimental deflections of the geomagnetic field regardless of
their energetic status. Free-flight release experiments during spring migration revealed a significant difference in mean
directions between clear sky and overcast tests. The difference may indicate a compensatory response to wind drift or possibly
a need for celestial cues to calibrate the magnetic compass. Finally, this is the first demonstration of magnetic compass
orientation in a North American vireo.
Received: 15 December 1995/Accepted after revision: 24 March 1996 相似文献
8.
Michael P. Harris Francis Daunt Mark Newell Richard A. Phillips Sarah Wanless 《Marine Biology》2010,157(4):827-836
Most seabirds die outside the breeding season, but understanding the key factors involved is hampered by limited knowledge
of nonbreeding distributions. We used miniature geolocating loggers to examine the movements between breeding seasons of Atlantic
puffins Fratercula arctica from a major North Sea colony where numbers have declined in recent years, apparently due to increased overwinter mortality.
The most intensively used region was the northwestern North Sea but most puffins also made excursions into the east Atlantic
in the early winter. Ringing recoveries previously indicated that adults from British east coast colonies remained within
the North Sea and hence were spatially segregated from those breeding on the west throughout the year. Updated analyses of
ringing recoveries support results from geolocators suggesting that usage of Atlantic waters is a recent phenomenon. We propose
that the increased adult mortality is related to changes in distribution during the nonbreeding period and reflects worsening
conditions in the North Sea. 相似文献
9.
We conducted a phylogeographic study of the meiofaunal nemertean Ototyphlonemertes parmula, an apparent species complex from the littoral zone of coarse-grained beaches, using a 494-bp fragment of the mitochondrial
cytochrome oxidase 3 gene (cox3). Six populations from the Gulf and Atlantic coasts of Florida, two from New England, and one from the Caribbean were sampled
in March and August 2005. Three major lineages were identified, separated by cox3 sequence divergence of 16–18%, with partially overlapping ranges. Tests for hybridization using ISSR markers detected nuclear
gene exchange within but not between the major mitochondrial lineages, indicating the presence of cryptic species. One lineage
dominating the Atlantic coast of Florida shows no evidence of geographic structuring. Another lineage shows a phylogenetic
break between the Atlantic and Gulf coasts, suggesting that unsuitable habitat may act as a barrier to dispersal. Long-distance
migration is evidenced by shared haplotypes between Florida and the eastern Caribbean. Overall, the widespread distribution
of individual haplotypes and lack of structuring within geographic regions contrast with O. parmula’s strongly sediment-bound lifestyle. We speculate that dispersal of adults by storms and/or sediment transport may be more
important than few and potentially short-lived planktonic larvae to explain geographic diversity in O. parmula and may be important for meiofauna in general. 相似文献
10.
At the beginning of their offshore migration, hatchling sea turtles orient directly into oceanic waves as they swim away
from land. Recent experiments have demonstrated that hatchlings swimming underwater can determine the propagation direction
of waves by monitoring the circular movements they experience as waves pass above. During July and August 1993, we studied
how loggerhead sea turtle hatchlings (Caretta caretta L.) from the east coast of Florida, USA, responded to a range of wave parameters. We constructed a wave simulator to reproduce
in air the circular movements that normally occur beneath small ocean waves. Hatchlings suspended in air and subjected to
these orbital movements attempted to orient into simulated waves when periods and amplitudes were similar to those found near
the Florida coast. Orbital movements with longer periods (greater than 10 s), however, failed to elicit responses. The results
demonstrate that hatchling loggerheads can distinguish between waves with different periods and amplitudes, and that Florida
hatchlings respond most strongly to orbital movements closely resembling those of waves that occur near their natal beach.
Received: 28 May 1996 / Accepted: 17 September 1996 相似文献
11.
T. M. Bert 《Marine Biology》1986,93(2):157-170
Electrophoretically detectable variation in 38 proteins and color morphology were used to determine the evolutionary relationships of crabs of the genus Menippe (Xanthidae) in the southeastern USA. Both allele frequencies (=genotype) and color morphology (=phenotype) showed that one species, Menippe mercenaria, is probably a taxonomic supergroup composed of two taxa (semispecies). One taxon (the western Gulf form) is distributed from northwest Florida westward through Texas. The second (the peninsular Florida form) ranges through the Florida peninsula from northwest to east central Florida, and in North Carolina. The taxa appear to have hybridized in two discrete regions: in the Gulf of Mexico (northwest Florida) and in the Atlantic Ocean (east central Florida to South Carolina). The agreement of patterns of geographic variation in genotype and phenotype with the geological record and estimated times of divergence based on genetic distances suggests that the observed patterns are the product of the influence of Late Cenozoic changes in climate and geology. The Atlantic zone of hybridization was formed prior to the closure of the seaway across north Florida connecting the Gulf of Mexico and the Atlantic, and the northwest Florida zone at some time subsequent to the closure. The present distribution, and the location of zones of hybridization, between the two semispecies of M. mercenaria illustrate the importance of the interaction of historical geological and climatic events with ecological boundaries in determining the distribution and interactions of shallow water marine species. 相似文献
12.
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida,
were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment
of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite
allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular
variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites
and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and
northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida
Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant
for both microsatellites (Φ
CT = 0.016, P = 0.009) and mtDNA (Φ
CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic
heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly
less (P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly
less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective
population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability
between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality
of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups
have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood
analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups,
with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and
the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic
events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity
among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically
distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf. 相似文献
13.
Robert D. Ward Jennifer R. Ovenden Jennifer R. S. Meadows Peter M. Grewe Sigrid A. Lehnert 《Marine Biology》2006,148(3):599-607
Eight polymorphic microsatellite loci were analysed in six population samples from four locations of the Australian endemic
brown tiger prawn, Penaeus esculentus. Tests of Hardy–Weinberg equilibrium were generally in accord with expectations, with only one locus, in two samples, showing
significant deviations. Three samples were taken in different years from the Exmouth Gulf. These showed no significant heterogeneity,
and it was concluded that they were from a single panmictic population. A sample from Shark Bay, also on the west coast of
Australia, showed barely detectable differentiation from Exmouth Gulf (F
ST = 0 to 0.0014). A northeast sample from the Gulf of Carpentaria showed low (F
ST = 0.008) but significant differentiation from Moreton Bay, on the east coast. However, Exmouth Gulf/Shark Bay samples were
well differentiated from the Gulf of Carpentaria/Moreton Bay (F
ST = 0.047–0.063). The data do not fit a simple isolation by distance model. It is postulated that the east–west differentiation
largely reflects the isolation of east and west coast populations that occurred at the last glacial maximum when there was
a land bridge between north-eastern Australia and New Guinea. 相似文献
14.
Different patterns of phytoplankton distribution,cell size,species' composition and abundance 总被引:2,自引:0,他引:2
A survey of the phytoplankton in the eastern Atlantic Ocean south of the Gulf of Guinea was undertaken, covering the local cyclonic gyre in the neutral col between the South Subtropical gyre, the Equatorial Countercurrent and the coast of Africa. Phytoplankton distribution, cell size, and abundance displayed distinct patterns which are presumed to be related to differential environmental dependence. 相似文献
15.
Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico 总被引:4,自引:2,他引:2
Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA
waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic
differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci
within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence
for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations,
two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (R
ST=0.096, P≤0.0001) and mitochondrial DNA (Φ
ST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation
coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence
of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes
of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species
is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas
where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance
of genetic diversity in this species in regions where incidental human-induced mortality occurs.
相似文献
Lara D. AdamsEmail: |
16.
To date, movement patterns of juvenile sand tigers (Carcharias taurus) along the east coast of the USA have been loosely defined. Given the magnitude of the purported decline in the sand tiger population in the western North Atlantic (WNA), characterization of the species’ movement patterns throughout this broad area is essential for the effective management and recovery of this population. Using passive acoustic telemetry, pop-up satellite archival transmitting tags, and conventional fishery-dependent tag/recapture data, seasonal movements of juvenile sand tigers (ages 0–2 years; <125 cm fork length) were monitored between Maine and Florida along the US east coast from 2007 to 2013. Collectively, tag data indicated that juvenile sand tigers undergo extensive seasonal coastal migrations moving between summer (June–October) habitat (Maine to Delaware Bay) and winter (December–April) habitat (Cape Hatteras to central Florida) during the spring (April–June) and fall/early winter (October–December). Juvenile sand tigers occurred in a wide range of temperatures (9.8–26.9 °C) throughout the year, but spent the majority of their time in water from 12 to 20 °C. Given the extensive movements and continuous utilization of relatively shallow (<80 m) nearshore waters exhibited by these relatively small individuals throughout their first years of life, it is imperative that precautions be taken to limit negative effects of anthropogenic interactions on this species (i.e., fisheries bycatch, coastal degradation) in an effort to rebuild and sustain the WNA population. 相似文献
17.
DuBose B. Griffin Sally R. Murphy Michael G. Frick Annette C. Broderick John W. Coker Michael S. Coyne Mark G. Dodd Matthew H. Godfrey Brendan J. Godley Lucy A. Hawkes Thomas M. Murphy Kristina L. Williams Matthew J. Witt 《Marine Biology》2013,160(12):3071-3086
From 1998 to 2008, 68 adult female loggerhead sea turtles (Caretta caretta) were instrumented with platform transmitter terminals at nesting beaches in Georgia, North Carolina (NC) and South Carolina (SC) on the East Coast of the United States of America (30°48′N, 81°28′W to 33°51′N, 77°59′W). The majority of post-nesting loggerheads (N = 42, 62 %) migrated to foraging habitats in the Mid-Atlantic Bight during May–October, with a subsequent migration occurring during November–March to foraging habitats south of Cape Hatteras, NC. Nine (13 %) loggerheads initially foraged in the near-shore, coastal areas of the South Atlantic Bight, but moved to offshore habitats—closer to the Gulf Stream—during November–March, while fourteen (21 %) loggerheads remained in foraging areas along the mid-continental shelf off of the eastern coast of Florida and/or continued southward to Florida Bay and the Bahamas. The present study delineates important, post-nesting foraging habitats and migration corridors where loggerheads may interact with commercial fisheries—providing managers opportunities to develop and implement optimally effective conservation actions for the recovery of this threatened species. 相似文献
18.
Eric R. Hoffmayer James S. Franks William B. Driggers III Jennifer A. McKinney Jill M. Hendon Joseph M. Quattro 《Marine Biology》2014,161(4):911-924
The dusky shark (Carcharhinus obscurus) is the largest member of the genus Carcharhinus and inhabits coastal and pelagic ecosystems circumglobally in temperate, subtropical and tropical marine waters. In the western North Atlantic Ocean (WNA), dusky sharks are overfished and considered vulnerable by the International Union for the Conservation of Nature. As a result, retention of dusky sharks in commercial and recreational fisheries off the east coast of the United States (US) and in the northern Gulf of Mexico is prohibited. Despite the concerns regarding the status of dusky sharks in the WNA, little is known about their habitat utilization. During the summers of 2008–2009, pop-up satellite archival tags were attached to ten dusky sharks (one male, nine females) at a location where they have been observed to aggregate in the north central Gulf of Mexico southwest of the Mississippi River Delta to examine their movement patterns and habitat utilization. All tags successfully transmitted data with deployment durations ranging from 6 to 124 days. Tag data revealed shark movements in excess of 200 km from initial tagging locations, with sharks primarily utilizing offshore waters associated with the continental shelf edge from Desoto Canyon to the Texas/Mexican border. While most sharks remained in US waters, one individual moved from the northern Gulf of Mexico into the Bay of Campeche off the coast of Mexico. Sharks spent 87 % of their time between 20 and 125 m and 83 % of their time in waters between 23 and 30 °C. Since dusky sharks are among the most vulnerable shark species to fishing mortality, there is a recovery plan in place for US waters; however, since they have been shown to make long-distance migrations, a multi-national management plan within the WNA may be needed to ensure the successful recovery of this population. 相似文献
19.
Thomas A. Jefferson Dagmar Fertl Jaime Bolaños-Jiménez Alexandre N. Zerbini 《Marine Biology》2009,156(6):1109-1124
Due to indications that misidentification (largely confusion among dolphins of the genera Delphinus and Stenella) in the past had led to erroneous assumptions of distribution of the two species of common dolphins (Delphinus delphis and D. capensis) in the western Atlantic Ocean, we conducted a critical re-examination of records of the genus Delphinus from this region. We compiled 460 ‘plottable’ records, required support for confirmation of genus and species identifications,
and found many records lacking (and some clearly misidentified). When we plotted only the valid records (n = 364), we found evidence of populations in only three areas, and apparent absence throughout much of the tropical/subtropical
regions. Off the east coast of the US and Canada, D. delphis is found from the Georgia/South Carolina border (32°N) north to about 47–50°N off Newfoundland. Since the 1960s, they have
apparently been absent from Florida waters. There is no evidence that dolphins of the genus occur in the Gulf of Mexico. Reports
of common dolphins from most of the Caribbean Basin are also rejected, and the only place in that region where they are confirmed
to occur is off central-eastern Venezuela (a coastal D. capensis population). Off eastern South America, common dolphins appear to be restricted to south of 20°S. There is a coastal long-beaked
population found in the South Brazil Bight, and one or more short-beaked populations south and offshore of this (ranging south
to at least northern Argentina). The results are very different from commonly-accepted patterns of distribution for the genus
in the Atlantic. Most areas of distribution coincide with moderate to strong upwelling and common dolphins appear to avoid
warm, tropical waters. This study shows that great care must be taken in identification of similar-appearing long-beaked delphinids,
and that uncritical acceptance of records at face value can lead to incorrect assumptions about the ranges of the species
involved. 相似文献
20.
The red porgy, Pagrus pagrus (L.), is a protogynous sparid associated with reefs and hard bottom habitat throughout the warm-temperate Atlantic Ocean.
In this study, the degree of geographic population differentiation in Atlantic populations was examined with microsatellite
and mitochondrial DNA markers (mtDNA). Six microsatellite loci were amplified and scored in 690 individuals from the eastern
North Atlantic (Crete, Madeira, and Azores), western North Atlantic (North Carolina to Florida, and the eastern Gulf of Mexico),
and Brazil. At two loci, fixed allelic differences were found among the three major geographic areas, while frequency differences
were observed at three other loci. The DNA of 371 individuals was amplified at the mtDNA control region, and 526 bp were sequenced.
Tamura–Nei’s D was used as a measure of nucleotide diversity and divergence: diversity averaged 0.011 within samples, while the corrected
divergence averaged 0 between samples within the same area and 0.061 between samples from different areas. Transversion haplotype
minimum spanning networks, nucleotide divergence, and F
ST values all show that the western Atlantic samples were more closely related to each other than any was to samples from the
eastern North Atlantic. Within the western North Atlantic, no significant population differentiation was observed, and within
the eastern North Atlantic, only the Azores sample showed detectable differences from Crete and Madeira. These data indicate
general homogeneity within large areas, and deep divisions between these areas.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献