A molecular analysis of relationships and biogeography within a species complex of Holarctic fish (genus Osmerus)

Abstract

Episodes of trans-Arctic faunal exchange and isolation between the north Pacific and Atlantic ocean basins have been implicated as important historic geological events contributing to extant patterns of genetic diversity and structure in Holarctic faunas. We made a further test of the significance of such biogeographic events by examining mitochondrial DNA (mtDNA) restriction fragment length and cytochrome b sequence polymorphism among north Pacific and Arctic, north-western Atlantic (north-eastern North American), and north-eastern Atlantic (European) regional forms of the boreal smelt, genus Osmerus. Our analyses also assessed whether the regional forms within this 'species complex': (i) represent a single widely distributed and polytypic species, or is composed of three geographically distinct species, and (ii) resulted from a single split from north Pacific ancestral Osmerus or two independent Pacific-Atlantic divergences. MtDNA sequence divergence estimates among forms ranged from 5.6-8.9% and from 6.1-8.5% based on restriction fragment and 300 base pairs of cytochrome b sequencing, respectively. Divergence within forms averaged less than 0.5% for fragment analysis and no differences were detected from sequence analysis. Provisional dating of lineage separations in Osmerus based on our sequence divergence estimates suggested a mid-Pliocene to early Pleistocene time frame for diversification among the forms. These estimated lineage separation dates support the idea that geological events in 'Beringia' and the surrounding trans-Arctic area (e.g. opening of the Bering Seaway, Pleistocene glacial advances), occurring over a similar time frame, have influenced radiation in Osmerus. Phenetic and parsimony analyses of the sequence divergence estimates and of sequence polymorphisms suggested that the north Pacific/Arctic form and the north-western Atlantic form shared a common ancestor more recently than either has with the north-eastern Atlantic form, thus supporting the hypothesis that the species complex has arisen from two independent Pacific-Atlantic divergences probably beginning during the mid-Pliocene.

Phylogenetic Relationships within GenusLeuciscus(Pisces, Cyprinidae) in Portuguese Fresh Waters, Based on Mitochondrial DNA CytochromebSequences

“…The mean observed percentage differences between cytochrome b sequences from distinct Iberian Leuciscus clades range from 5.1 to 10.7%. Values in the same order of magnitude were reported for genera Osmerus (Taylor and Dodson, 1994) and Gasterosteus (Orti et al, 1994). Higher interspecific divergence values were reported for genus Melanotaenia, but this genus occurs in a vast area including Australia and New Guinea (Zhu et al, 1994).…”

Molecular genetic analyses of species boundaries in the sea

“…Additional analyses of species boundaries not cited by these authors include studies of Myliobatis (Levy & Conceição, 1989), Siganus (Lacson & Nelson, 1993), Naso (Dayton et al, 1994), Pleuronichthys (Watanabe et al, 1994), Osmerus (Taylor & Dodson, 1994), several damselfish genera (Lacson, 1994;Lacson & Clark, 1995;Lessios et al, 1995), Lutjanus (Lee & Cheng, 1996), Trematomus (Bernardi & Goswami, 1997), Cyclothone (Miya & Nishida, 1997), Mugil (Rossi et al, 1998), andChaetodon (McMillan et al, 1999).…”

Genetic divergence of tanaidaceans (Crustacea: Peracarida) with low dispersal ability

“…Recently, gene flow between the Pacific and the Atlantic has been detected for several marine taxa; it is generally accepted that dispersal often goes in the Pacific-Atlantic direction (Teeter 1973, Meehan et al 1989, Palumbi and Wilson 1990, Palumbi and Kessing 1991, Taylor and Dodson 1994, Rawson and Hilbish 1995, van Oppen et al 1995, Väinölä 2003. Gene flow related to inter-glacial periods is suggested for a number of invertebrates, including littoral bivalves (Väinölä 2003), sea urchins (Addison and Hart 2005), crabs (Harrison and Crespi 1999) and even peracarids, such as mysids (Audzijonytė et al 2005).…”