No abstract

Phylogenetic analysis of 13 substantially complete mitochondrial DNA genome sequences (14,036 bp) from 10 taxa of gadine codfishes and pollock provides highly corroborated resolution of outstanding questions on their biogeographic evolution. Of 6 resolvable nodes among species, 4 were supported by >95% of bootstrap replications in parsimony, distance, likelihood, and similarly high posterior probabilities in bayesian analyses, one by 85%-95% according to the method of analysis, and one by 99% by one method and a majority of the other two. The endemic Pacific species, walleye pollock (Theragra chalcogramma), is more closely related to the endemic Atlantic species, Atlantic cod (Gadus macrocephalus), than either is to a second Pacific endemic, Pacific cod (Gadus macrocephalus). The walleye pollock should thus be referred to the genus Gadus as originally described (Gadus chalcogrammus Pallas 1811). Arcto-Atlantic Greenland cod, previously regarded as a distinct species (G. ogac), are a genomically distinguishable subspecies within pan-Pacific G. macrocephalus. Of the 2 endemic Arctic Ocean genera, Polar cod (Boreogadus) as the outgroup to Arctic cod (Arctogadus) and Gadus sensu lato is more strongly supported than a pairing of Boreogadus and Arctogadus as sister taxa. Taking into consideration historical patterns of hydrogeography, we outline a hypothesis of the origin of the 2 endemic Pacific species as independent but simultaneous invasions through the Bering Strait from an Arcto-Atlantic ancestral lineage. In contrast to the genome data, the complete proteome sequence (3830 amino acids) resolved only 3 nodes with >95% confidence, and placed Alaska pollock outside the Gadus clade owing to reversal mutations in the ND5 locus that restore ancestral, non-Gadus, amino acid residues in that species.

We report that a single nucleotide replacement in the melanocortin 1 receptor gene [1] (mc1r) is responsible for the white coat color of the "Kermode" bear [2], a color phase of the black bear (Ursus americanus Pallus) found in the rainforests along the north coast of British Columbia. In a sample of 220 bears, of which 22 were white, there was complete association of a recessive Tyr-to-Cys replacement at codon 298 with the white phase. This variant has not been yet been reported in other mammals, and it also is the lightest-colored variant yet found at mc1r. Also, we found that heterozygotes, which act as a hidden reservoir for the allele among black bears, were infrequent outside of the three islands where Kermodes are common and that, within these three islands, heterozygotes were less frequent than expected under random mating. Immigration of black bears into Kermode populations can depress the occurrence of the white phase, and management practices should be designed to avoid facilitating higher immigration rates.

SUMMARYMultiple sources of evidence show that the skuas (Aves : Stercorariidae) are a monophyletic group, closely related to gulls (Laridae). On morphological and behavioural evidence the Stercorariidae are divided into two widely divergent genera, atharacta and Stercorarius, consistent with observed levels of nuclear and mitochondrial gene divergence. atharacta skuas are large-bodied and with one exception breed in the Southern Hemisphere. Stercorarius skuas (otherwise known as jaegers) are smaller bodied and breed exclusively in the Northern Hemisphere. Evidence from both mitochondrial and nuclear genomes and from ectoparasitic lice (Insecta : Phthiraptera) shows that the Pomarine skua, S. pomarinus, which has been recognized as being somewhat intermediate in certain morphological and behavioural characteristics, is much more closely related to species in the genus atharacta, especially to the Northern Hemispherebreeding Great skua, . skua, than it is to the other two Stercorarius skuas, the Arctic skua, S. parasiticus and the Longtailed skua, S. longicaudus. Three possible explanations that might account for this discordant aspect of skua phylogeny are explored. These involve (i) the segregation of ancestral polymorphism, (ii) convergent evolution of morphology and behaviour or (iii) inter-generic hybridization. The available evidence from both nuclear and mitochondrial genomes does not exclude any of these hypotheses. Thus, resolution of this enigma of skua phylogeny awaits further work.