Mitochondrial DNA variation in Atlantic capelin, Mallotus villosus: a comparison of restriction and sequence analyses

Genetic structure of capelin (Mallotus villosus) in the northwest Atlantic Ocean

Capelin (Mallotus villosus) is a commercially exploited, key forage-fish species found in the boreal waters of the North Pacific and North Atlantic Oceans. We examined the population structure of capelin throughout their range in the Canadian northwest Atlantic Ocean using genetic-based methods. Capelin collected at ten beach and five demersal spawning locations over the period 2002 through 2008 (N = 3,433 fish) were genotyped using six polymorphic microsatellite loci. Temporally distinct samples were identified at three beach spawning locations: Chance Cove, Little Lawn and Straitsview, Newfoundland. Four capelin stocks are assumed for fisheries management in the northwest Atlantic Ocean based on meristics, morphometrics, tag returns, and seasonal distribution patterns. Our results suggested groupings that were somewhat different than the assumed structure, and indicate at least seven genetically defined populations arising from two ancestral populations. The spatial mosaic of capelin from each of the two basal cluster groups explains much of the observed geographic variability amongst neighbouring samples. The genetic-defined populations were resolved at Jost’s D_est ≥ 0.01 and were composed of fish collected 1) in the Gulf of St. Lawrence, 2) along the south and east coasts of Newfoundland, 3) along coastal northern Newfoundland and southern Labrador, 4) along coastal northern Labrador, 5) near the Saguenay River, and at two nearshore demersal spawning sites, 6) one at Grebes Nest off Bellevue Beach on the east coast of Newfoundland, and 7) one off the coast of Labrador at Domino Run. Moreover, the offshore demersal spawners on the Scotian Shelf and Southeast Shoal appeared to be related to the inshore demersal spawners at Grebes Nest and in Domino Run and to beach spawners from the Gulf of St. Lawrence.

Phylogeny and evolution of the Sulidae (Aves:Pelecaniformes): a test of alternative modes of speciation

Although the allopatric model of speciation is widely accepted, it does not provide a satisfactory explanation for many evolutionary phenomena. Several alternative models exist, but they remain largely untested for vertebrate animals. In the present paper, a molecular phylogeny was used to test competing models of speciation in a seabird family, the Sulidae. A segment including 807 base pairs of the mitochondrial cytochrome b gene was sequenced from all extant sulid species, and phylogenetic methods were used to test model-specific predictions regarding tree topologies, distributions of sister taxa, timing of vicariant events, and comparative biology. Both the neighbor-joining and parsimony analyses placed sequences of gannets (Morus spp.) and boobies of the genus Sula in separate, monophyletic lineages. Sequences of Cape (M. capensis) and Australasian (M. serrator) gannets clustered together, and the sequence of Abbott's booby (Papasula abbotti) was basal to those of the gannets. Sequences of blue-footed (S. nebouxii) and Peruvian (S. variegata) boobies were sisters and formed a monophyletic group with the masked booby (S. dactylatra). The red-footed booby (S. sula) sequence was the most divergent of the Sula boobies. All relationships received strong support from standard-error tests and bootstrap analysis. Substitution rates were similar to those suggested for mammals and suggested that most lineages arose within the last 3 million years. Lineage divergence events for which the mode of speciation could be deduced did not fit the predictions of either allopatric or sympatric models, but apparently involved either peripatric or parapatric processes.