Date Speaker Field
18th April Amanda Phylogeny
9th May Catherine Phylogeography
16th May Emilie Population genetics
23rd May Ilkser Phylogeny
30th May Mpho Phylogeography
6th June Tim Population genetics
13th June Paulette Phylogeny
20th June Amanda Population genetics
27th June Carel Phylogeography
4th July Kerry Phylogeny
25th July Miekie Phylogeography
1st August Sam Population genetics
8th August Sarita Phylogeography
Monday, April 11, 2011
The speciation genes
Today, Amanda will present an opinion paper discussing about the need for the definition of the speciation genes, i.e. genes involve in reproductive isolation prior to the actual speciation event. They propose a definition for these genes based on several assumptions. Then they present some examples of such genes. Thanks Amanda.
From Nosil P & Schluter D, Trends in Ecology and Evolution, April 2011, Vol. 26, No. 4: 160-167
Title: The genes underlying the process of speciation
Abstract
The long-standing goal of finding genes causing reproductive isolation is being achieved. To better link the genetics with the process of speciation, we propose that ‘speciation gene’ be defined as any gene contributing to the evolution of reproductive isolation. Characterizing a speciation gene involves establishing that the gene affects a component of reproductive isolation; demonstrating that divergence at the locus occurred before completion of speciation; and quantifying the effect size of the gene (i.e. the increase in total reproductive isolation caused by its divergence). Review of a sample of candidate speciation genes found that few meet these criteria. Improved characterization of speciation genes will clarify how numerous they are, their properties and how they affect genome-wide patterns of divergence.
Allopatric speciation in reef fish
A while ago, Kerry presented a paper presenting a study aiming to evaluate the mode of speciation in an Indo-Pacific reef fish species complex: Dascyllus trimaculatus. From both mt DNA sequences and a set of 16 microsatellites, they defined the population/species boundaries between the different groups morphologically distinct. From their results, they found that the mode of speciation in this taxon fit well with allopatry, but found some support for additional factors such as ecological factors. Thanks Kerry.
From Leray M, Beldade R, Holbrook SJ, Schmitt RJ, Planes S and Bernardi G. Evolution, 2009, 64-5: 1218–1230
Title: Allopatric divergence and speciation in coral reef fish: the three-spot dascilllus, Dascillus trimaculatus, species complex
Abstract
Long pelagic larval phases and the absence of physical barriers impede rapid speciation and contrast the high diversity observed in marine ecosystems such as coral reefs. In this study, we used the three-spot dascyllus (Dascyllus trimaculatus) species complex to evaluate speciation modes at the spatial scale of the Indo-Pacific. The complex includes four recognized species and four main color morphs that differ in distribution. Previous studies of the group using mitochondrial DNA revealed a non congruence between color morphs and genetic groupings; with two of the color morphs grouped together and one color morph separated into three clades. Using extensive geographic sampling of 563 individuals and a combination of mitochondrial DNA sequences and 13 nuclear microsatellites, we defined population/species boundaries and inferred different speciation modes. The complex is composed of seven genetically distinct entities, some of which are distinct morphologically. Despite extensive dispersal abilities and an apparent lack of barriers, observed genetic partitions are consistent with allopatric speciation. However, ecological pressure, assortative mating, and sexual selection, were likely important during periods of geographical isolation. This study therefore suggests that primarily historical factors later followed by ecological factors caused divergence and speciation in this group of coral reef fish.
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