Conservation implications of the genetic and ecological distinction of Tursiops truncatus ecotypes in the Gulf of California

Segura, Iris; Rocha‐Olivares, Axayácatl; Flores-Ramírez, Sergio; Rojas‐Bracho, Lorenzo

doi:10.1016/j.biocon.2006.06.017

Cited by 64 publications

(92 citation statements)

References 44 publications

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“…Tursiops truncatus is found in both coastal and offshore habitats along the Mauritanian coastline (Robineau & Vely 1998). This probably explains the large intraspecific variability in the δ 13 C values and suggests the occurrence of persistent individual differences in foraging habits or even the existence of coastal versus offshore populations and/or ecotypes in the area, as has been found elsewhere (Segura et al 2006).Nevertheless, the mean δ 13 C value of Tursiops truncatus was close to that of Globicephala melas, a typical deepwater species in the North Atlantic (MacLeod et al 2007) that is also known to occur over the continental shelf off Banc d'Arguin and off the Grande Plage (Maigret et al 1976, Robineau & Vely 1998 (Robineau & Vely 1998). This observation does not seem to correlate with the typical prey of the 2 species of Globicephala (Overholtz & Waring 1991).…”

supporting

confidence: 54%

Stable isotope analysis reveals habitat partitioning among marine mammals off the NW African coast and unique trophic niches for two globally threatened species

Pinela¹,

Borrell²,

Cardona³

et al. 2010

Mar. Ecol. Prog. Ser.

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Stable isotope abundances of carbon (δ 13 C) and nitrogen (δ 15 N) in the bone of 13 species of marine mammals from the northwest coast of Africa were investigated to assess their positions in the local trophic web and their preferred habitats. Also, samples of primary producers and potential prey species from the study area were collected to characterise the local isotopic landscape. This characterisation indicated that δ 13 C values increased from offshore to nearshore and that δ 15 N was a good proxy for trophic level. Therefore, the most coastal species were Monachus monachus and Sousa teuszii, whereas the most pelagic were Physeter macrocephalus and Balaenoptera acutorostrata. δ 15 N values indicated that marine mammals located at the lowest trophic level were B. acutorostrata, Stenella coeruleoalba and Delphinus sp., and those occupying the highest trophic level were M. monachus and P. macrocephalus. The trophic level of Orcinus orca was similar to that of M. monachus, suggesting that O. orca preys on fish. Conservation of coastal and threatened species (M. monachus and S. teuszii ) off NW Africa should be a priority because these species, as the main apex predators, cannot be replaced by other marine mammals. KEY WORDS: Marine mammals · Stable isotopes · Trophic ecology · Habitat use · NW Africa Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 416: [295][296][297][298][299][300][301][302][303][304][305][306] 2010 cies, such as the Mediterranean monk seal Monachus monachus (González et al. 1997), the Atlantic humpback dolphin Sousa teuszii (Van Waerebeek et al. 2004) and the African manatee Trichechus senegalensis (Padial & Ibáñez 2005). Mauritania is one of the major African fishing nations and has developed, alongside traditional artisanal fishing, industrial fisheries, becoming one of the major fish exporting African countries (Ababouch 2000). Overfishing, overcapacity, habitat degradation and inequitable access agreements have contributed to the decline in catches throughout West Africa (Atta-Mills et al. 2004, ter Hofstede & DickeyCollas 2006. Assessing the impact of fisheries on the local ecosystem is of great interest (Jouffre & Inejih 2005) but no studies have been conducted involving marine mammals.Available information on the marine mammals of the region is limited to stranding and sighting reports in the case of cetaceans (Duguy 1976, Maigret 1980a,b, 1981, Marchessaux & Campredon 1988, Van Waerebeek et al. 1999, although a few demographic parameters are known for Monachus monachus (González et al. 1997. Nevertheless, the trophic relationships among the marine apex predators of the region have never been investigated, and their possible interactions with the fisheries operating in the area are largely unknown.The methods traditionally used in the study of the trophic ecology of marine mammals have been faecal or stomach-content analyses. These methods present limitations because they only show recently eaten prey, and results can be se...

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supporting

confidence: 54%

Stable isotope analysis reveals habitat partitioning among marine mammals off the NW African coast and unique trophic niches for two globally threatened species

Pinela¹,

Borrell²,

Cardona³

et al. 2010

Mar. Ecol. Prog. Ser.

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“…The absence of a genetically differentiated coastal ecotype around the North-East Atlantic Islands was unexpected, given the prevalence of this finding in the Atlantic and Pacific Oceans (Hoelzel et al 1998b;Segura et al 2006) and the pattern of residency observed in the Azores (Silva 2006). However, it is consistent with the steep topography of the area, with deep waters occurring at short distances from the coast.…”

Section: Discussionmentioning

confidence: 97%

“…In the North-West Atlantic, the pelagic ecotype occurs mainly in waters beyond 34 km from shore and 34 m depth while the coastal one occurs at least up to 7.5 km from shore (Torres et al 2003). In the Gulf of California, a distribution break is found around the 60m-isobath (Segura et al 2006). At a regional scale, genetic analyses evidenced differentiation between the eastern and western basins of the Mediterranean Sea (Natoli et al 2005), as well as between coastal populations of the Gulf of Mexico (Sellas et al 2005) and the Northern Bahamas (Parsons et al 2006).…”

Section: Introductionmentioning

confidence: 99%

High gene flow in oceanic bottlenose dolphins (Tursiops truncatus) of the North Atlantic

et al. 2007

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Despite the openness of the oceanic environment, limited dispersal and tight social structure often induce genetic structuring in marine organisms, even in large animals such as cetaceans. In the bottlenose dolphin, mitochondrial and nuclear DNA analyses have revealed the existence of genetic differentiation between pelagic (or offshore) and coastal (or nearshore) ecotypes in the western North Atlantic, as well as between coastal populations. Because previous studies concentrated on continental margins, we analysed the population structure of bottlenose dolphins in two of the most isolated archipelagos of the North Atlantic: the Azores and Madeira. We analysed 112 samples collected on live animals in the two archipelagos, and nine samples collected on stranded animals in Madeira and mainland Portugal. Genetic analyses consisted in molecular sexing, sequencing of part of the mitochondrial hypervariable region, and screening of ten microsatellite loci. We predicted that: 1/ there is at least one pelagic and one or more coastal populations in each archipelago; 2/ populations are differentiated between and possibly within archipelagos. Contrary to these predictions, results indicated a lack of population structure in the study area. In addition, comparison with published sequences revealed that the samples from the Azores and Madeira were not significantly differentiated from samples of the pelagic population of the western North Atlantic. Thus, bottlenose dolphins occurring in the pelagic waters of the North Atlantic belong to a large oceanic population, which should be regarded as a single conservation unit. Unlike what is known for coastal populations, oceanic bottlenose dolphins are able to maintain high levels of gene flow.

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“…Among cetacean species, both killer whales (Orcinus orca) and bottlenose dolphins (Tursiops truncatus) show genetic differentiation among populations correlated to foraging specializations or habitat dependence (O. orca, Hoelzel et al, 2007;Moura et al, 2014;T. truncatus, Hoelzel et al, 1998;Natoli et al, 2005;Segura et al, 2006;CharltonRobb et al, 2011;Moura et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…There is also often genetic differentiation between coastal and pelagic populations, such as for the bottlenose dolphins in the North Atlantic and North Pacific (T. truncatus; see, for example, Natoli et al, 2005;Segura et al, 2006;Lowther-Thieleking et al, 2015) and for the eastern tropical Pacific pantropical spotted dolphins (Stenella attenuata; Escorza-Treviño et al, 2005). In some cases ecological phenotypes associated with habitat have been assigned specific status, such as the pelagic (T. truncatus) and coastal (Tursiops aduncus) forms of bottlenose dolphins in Asia (Wang et al, 1999) and Australasia (Möller and Beheregaray, 2001), and the riverine (Sotalia fluvitalis) and coastal (Sotalia guianensis) forms of the 'tucuxi' dolphin (Caballero et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Post-glacial habitat release and incipient speciation in the genus Delphinus

et al. 2016

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The role of ecological and changing environmental factors in the radiation of species diversity is a fundamental question in evolutionary biology. Of particular interest is the potential for these factors to determine the boundary between what we would consider differentiation among populations and incipient speciation. Dolphins in the genus Delphinus provide a useful test case, exhibiting morphological variation in beak length, coloration and body size across their wide geographic distribution, and in particular among coastal and more pelagic habitats. Two species have been proposed, D. delphis and D. capensis, but morphologically similar allopatric populations are not monophyletic, indicating that the mostly coastal 'long-beaked' D. capensis form is not a single globally distributed species. However, the sympatric populations in the Eastern North Pacific currently designated as these two species are both morphologically and genetically differentiated. Here we use microsatellite DNA and mitochondrial DNA markers to investigate the evolutionary mechanisms that led to this incipient speciation event. We used coalescent and assignment methods to investigate the timing and extent of reproductive isolation. Our data indicate that although there is some level of on-going gene flow, the putative species found in the Eastern North Pacific are reciprocally monophyletic. The timing of isolation appears to be associated with regional changes in paleoceanographic conditions within the Holocene timeframe.

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Conservation implications of the genetic and ecological distinction of Tursiops truncatus ecotypes in the Gulf of California

Cited by 64 publications

References 44 publications

Stable isotope analysis reveals habitat partitioning among marine mammals off the NW African coast and unique trophic niches for two globally threatened species

Stable isotope analysis reveals habitat partitioning among marine mammals off the NW African coast and unique trophic niches for two globally threatened species

High gene flow in oceanic bottlenose dolphins (Tursiops truncatus) of the North Atlantic

Post-glacial habitat release and incipient speciation in the genus Delphinus

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