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302 j A. Rus Hoelzel using vs .net toconnect code39 in web,windows application QR Code Safty 1987; Perrin .net framework 39 barcode 2002a). The common dolphin (Delphinus spp.

) also shows morphotypic differentiation, with coastal populations having longer beaks and distinct colour patterns (Perrin 2002b). Heyning and Perrin (1994) proposed that the two common dolphin forms in the eastern tropical Pacific are sufficiently different to justify separate specific classification, and proposed D. capensis for the long-beaked form.

A genetic study based on mtDNA sequences suggested significant differentiation between these forms off southern California, but the sample size was small (12 shortbeaked and 11 long-beaked forms: Rosel et al. 1994). A recent study investigating mtDNA control region variation and microsatellite DNA diversity for putative long and short-beaked Delphinus populations worldwide found no correlation between morphotype and genetic differentiation (Natoli et al.

2006). The long-beaked animals from Rosel et al. (1994) formed a monophyletic lineage well separated from the rest of the samples, but long- and short-beaked forms from elsewhere in the world were fully polyphyletic.

Natoli et al. (2006) suggested that regional coastal populations adapted to the habitat with similar morphology several times independently (convergent evolution). The best-known example of coastal and pelagic morphotypes is for bottlenose dolphins (Tursiops spp.

). In the western North Atlantic the coastal Tursiops truncatus form is relatively smaller and differs in cranial morphology from the pelagic form (Mead and Potter 1995; Hoelzel et al. 1998b).

Parasite load also differs, consistent with the parasite species found in their respective habitats (Mead and Potter 1995). Coastal schools are typically found within 8 km of the coast, while the pelagic schools are usually found 34+ km from shore (though their ranges sometime overlap: Torres et al. 2003).

Foraging differences were evident from both stomach contents and stable isotope analyses (Mead and Potter 1995; Cortese 2000), with the pelagic form taking more cephalopod prey, and the coastal form more fish. Hoelzel et al. (1998a) investigated the genetic structure of these populations, and found highly significant differentiation between the coastal and pelagic forms both for mtDNA control region sequences (ST = 0.

604) and microsatellite DNA loci (RST = 0.373). A similar pattern has been found for the coastal and pelagic populations found off southern California (Lowther et al.

2005). Those populations also show morphometric differentiation, but in that case it is the pelagic form that is smaller (Walker 1981). In both studies the coastal form showed lower levels of diversity, suggesting a possible historical founder event.

A preliminary study of putative coastal and pelagic forms of T. truncatus off the South African coast showed no differentiation, but the sample size was small. Genetic structure in marine mammal species j 303 (Hoelzel et a .NET ANSI/AIM Code 39 l. 1998b).

However, a coastal population of morphologically distinct bottlenose dolphins (the aduncus form, Ross 1977) inhabiting the Natal coast of South Africa was highly differentiated from both pelagic and coastal truncatus forms (Natoli et al. 2004). The distinction was sufficient to justify classification as a new species, T.

aduncus, though equally divergent from a morphologically similar form found in Asian waters, also designated T. aduncus (Wang et al. 1999; Natoli et al.

2004). This coastal form has a relatively long beak, as for the coastal Delphinus forms, which may reflect convergent evolution in similar habitat (see Natoli et al. 2006 and above).

Dolphin populations that are found in coastal habitat often show finescale population structure. In a study comparing bottlenose dolphin samples collected across the contiguous range from Scotland to the Black Sea, a likelihood assignment method (STRUCTURE : Pritchard et al. 2000) clustered samples to apparent habitat regions (Natoli et al.

2005) (Fig. 13.4, also Plate 2, colour plate section).

When possible (power is relatively low), this type of clustering method (based on genotypes and equilibrium models, and not a priori assignment to putative populations) is especially useful for marine mammal species, since boundaries to gene flow are often cryptic in the marine environment. The identified boundaries for bottlenose dolphins between the North Atlantic and Mediterranean, and between the eastern and western basins of the Mediterranean are separated by open water (rather than boundaries defined by land mass), but oceanic conditions distinguish these regions. In each case a number of other species also show genetic differentiation across a similar geographic range (see Natoli et al.

2005). The diet of the dolphins in the study by Natoli et al. (2005) was not known, but other studies have shown clear differences in feeding behaviour for this species in different coastal habitats.

For example, Gannon and Waples (2004) describe prey choice differences between populations in open coastal versus estuarine habitat in Florida. If local populations are dependent on different prey resources, and if that dependence affects dispersal behaviour, this could serve as a mechanism for reducing gene flow. One way foraging specializations could affect dispersal behaviour would be through the social facilitation of foraging.

Remaining in natal social groups (or within a broader affiliation of social groups) to learn foraging strategies appropriate to a given habitat could be beneficial provided that some individuals still dispersed (to avoid inbreeding depression). This would suggest a frequency dependent strategy. It does not imply a bias in benefit for dispersal in one sex over the other, and consistent with this Natoli et al.

(2005) found no evidence of sex-biased dispersal. Sellas et al. (2005) describe a similar pattern of fine-scale population structure in the.

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