Genetic structure of harbour porpoise Phocoena phocoena populations in the northwest Atlantic based on mitochondrial and nuclear markers

A genetic assessment of polyandry and breeding-site fidelity in lemon sharks

We here employ 11 microsatellite markers and recently developed litter reconstruction methods to infer mating system parameters (i.e. polyandry and breeding-site fidelity) at a lemon shark nursery site in Marquesas Key, Florida. Four hundred and eight juvenile or subadult sharks were genotyped over eight complete breeding seasons. Using this information, we were able to infer family structure, as well as fully or partially reconstruct genotypes of 46 mothers and 163 fathers. Multiple litter reconstruction methods were used, and novel simulations helped define apparent bias and precision of at least some mating system parameters. For Marquesas Key, we find that adult female lemon sharks display high levels of polyandry (81% of all litters sampled) and stronger fidelity to the nursery site than do males. Indeed, few male sharks sired offspring from more than one litter during the course of the study. These findings were quite similar to previous results from another lemon shark nursery site (Bimini, Bahamas), suggesting conserved mating system parameters despite significant variation in early life-history traits (i.e. body size and growth) among sites. The finding of at least some site fidelity in females also supports the need for careful conservation of each nursery.

Social kin associations and genetic structuring of striped dolphin populations (Stenella coeruleoalba) in the Mediterranean Sea

We investigated hierarchical patterns of genetic subdivision, and assessed kinship within and between social groups of striped dolphins (Stenella coeruleoalba) in the Tyrrhenian Sea. A total of 165 samples were analysed at eight microsatellite DNA loci, including outgroup samples from the Adriatic, Scotland and Spain for population-level comparisons. We found population genetic structure within the Mediterranean basin, including small but significant differentiation between the Adriatic and Tyrrhenian Seas (FST=0.0047, P=0.008), and between putative 'inshore' and 'offshore' (FST=0.0217, P=0.005) populations in the Tyrrhenian Sea. Assessment of kinship within and among 12 association groups showed higher average kinship for females within than between groups, and smaller groups showed higher average kinship. Comparisons of relatedness for both sexes showed a significant difference between males and females, with females more likely to associate with adult kin. Together these data emphasize the importance of the social cohesion of kin in small groups to the structuring of striped dolphin populations in this environment.

Nuclear and mitochondrial markers reveal distinctiveness of a small population of bottlenose whales (Hyperoodon ampullatus) in the western North Atlantic

Small populations at the edge of a species' distribution can represent evolutionary relics left behind after range contractions due to climate change or human exploitation. The distinctiveness and genetic diversity of a small population of bottlenose whales in the Gully, a submarine canyon off Nova Scotia, was quantified by comparison to other North Atlantic populations using 10 microsatellites and mitrochondrial DNA (mtDNA) control region sequences (434 bp). Both markers confirmed the distinctiveness of the Gully (n = 34) from the next nearest population, off Labrador (n = 127; microsatellites -F(ST)= 0.0243, P < 0.0001; mtDNA -Phi(ST) = 0.0456, P < 0.05). Maximum likelihood microsatellite estimates suggest that less than two individuals per generation move between these areas, refuting the hypothesis of population links through seasonal migration. Both males and females appear to be philopatric, based on significant differentiation at both genomes and similar levels of structuring among the sexes for microsatellites. mtDNA diversity was very low in all populations (h = 0.51, pi = 0.14%), a pattern which may be due to selective sweeps associated with this species' extreme deep-diving ecology. Whaling had a substantial impact on bottlenose whale abundance, with over 65 000 animals killed before the hunt ceased in the early 1970s. Genetic diversity was similar among all populations, however, and no signal for bottlenecks was detected, suggesting that the Gully is not a relic of a historically wider distribution. Instead, this unique ecosystem appears to have long provided a stable year-round habitat for a distinct population of bottlenose whales.

Pathological findings in harbour porpoises (Phocoena phocoena) from Norwegian and Icelandic waters

A study of 37 by-caught harbour porpoises from Icelandic and Norwegian waters showed that most were in good or moderate nutritional condition and none was severely emaciated. Mild infection with lungworms (Halocercus invaginatus, Pseudalius inflexus, Torynurus convolutus) was found in 84% of the Icelandic and 91% of the Norwegian animals, usually associated with bronchopneumonia which was rarely severe. Most (91%) of the animals had parasites in the stomach and intestine (Anisakis simplex, Contracaecum osculatum, Pholeter gastrophilus), and Campula oblonga was present in the liver and pancreas of 88 and 21%, respectively. Oesophagitis, gastritis, cholangitis, pericholangitis, pancreatitis and lymphadenitis were almost exclusively associated with parasitic infection and usually mild. Bacterial isolates were obtained from 50 to 55% of the animals but were not considered to be clinically significant. There was no indication of morbillivirus infection. Icelandic and Norwegian animals showed a thicker blubber layer and a lower incidence of severe lesions, especially in the respiratory tract, as compared with reports of by-caught animals from the Baltic Sea.

Multiple paternity in loggerhead turtle (Caretta caretta) nests on Melbourne Beach, Florida: a microsatellite analysis

Many aspects of sea turtle biology are difficult to measure in these enigmatic migratory species, and this lack of knowledge continues to hamper conservation efforts. The first study of paternity in a sea turtle species used allozyme analysis to suggest multiple paternity in loggerhead turtle (Caretta caretta) clutches in Australia. Subsequent studies indicated that the frequency of multiple paternity varies from species to species and perhaps location to location. This study examined fine-scale population structure and paternal contribution to loggerhead clutches on Melbourne Beach, FL, USA using microsatellite markers. Mothers and offspring from 70 nests collected at two locations were analysed using two to four polymorphic microsatellite loci. Fine-scale population differentiation was not evident between the sampled locations, separated by 8 km. Multiple paternity was common in loggerhead nests on Melbourne Beach; 22 of 70 clutches had more than one father, and six had more than two fathers. This is the first time that more than two fathers have been detected for offspring in individual sea turtle nests. Paternal genotypes could not be assigned with confidence in clutches with more than two fathers, leaving the question of male philopatry unanswered. Given the high incidence of multiple paternity, we conclude that males are not a limiting resource for this central Florida nesting aggregate.

DNA sequence variation in the mitochondrial control region of red-backed voles (Clethrionomys)

The complete mitochondrial DNA (mtDNA) control region was sequenced for 71 individuals from five species of the rodent genus Clethrionomys both to understand patterns of variation and to explore the existence of previously described domains and other elements. Among species, the control region ranged from 942 to 971 bp in length. Our data were compatible with the proposal of three domains (extended terminal associated sequences [ETAS], central, conserved sequence blocks [CSB]) within the control region. The most conserved region in the control region was the central domain (12% of nucleotide positions variable), whereas in the ETAS and CSB domains, 22% and 40% of nucleotide positions were variable, respectively. Tandem repeats were encountered only in the ETAS domain of Clethrionomys rufocanus. This tandem repeat found in C. rufocanus was 24 bp in length and was located at the 5' end of the control region. Only two of the proposed CSB and ETAS elements appeared to be supported by our data; however, a "CSB1-like" element was also documented in the ETAS domain.

Microsatellite variation in colonizing and palearctic populations of Drosophila subobscura

The recent colonization of North America by Drosophila subobscura has provided a great opportunity to analyze a colonization process from the beginning. A comparative study using 10 microsatellite loci was conducted for five European and two North American populations. No genetic differentiation between European populations was detected, indicating that gene flow is high among them and that the microsatellites used in the present work represent neutral markers not subject to differentiation due to selection. Extensive reduction in the number of alleles and a significant decrease in heterozygosity in colonizing populations were detected that could be explained by the founder effect and a subsequent quick but not infinite expansion. Assuming that all alleles present in the colonized area were carried by the sample of colonizers, we estimated that most probably 4-11 individuals expanded in the new area. F(ST) and the chord distance measures reflect the colonization process more accurately, since drift has been the major force in differentiating the Old and New World populations, and thus other measures considering allele size differences, such as Rho(ST) and deltamu2, are less reliable for studying nonequilibrium populations. Finally, our results were consistent with the two-phase microsatellite mutational model, indicating that most alleles are generated by gain or loss of a repeat unit, while some alleles originate by more complex mutations.