Article

Review. The genic view of plant speciation: Recent progress and emerging questions

Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK.
Philosophical Transactions of The Royal Society B Biological Sciences (Impact Factor: 7.06). 07/2008; 363(1506):3023-36. DOI: 10.1098/rstb.2008.0078
Source: PubMed

ABSTRACT

The genic view of the process of speciation is based on the notion that species isolation may be achieved by a modest number of genes. Although great strides have been made to characterize 'speciation genes' in some groups of animals, little is known about the nature of genic barriers to gene flow in plants. We review recent progress in the characterization of genic species barriers in plants with a focus on five 'model' genera: Mimulus (monkey flowers); Iris (irises); Helianthus (sunflowers); Silene (campions); and Populus (poplars, aspens, cottonwoods). The study species in all five genera are diploid in terms of meiotic behaviour, and chromosomal rearrangements are assumed to play a minor role in species isolation, with the exception of Helianthus for which data on the relative roles of chromosomal and genic isolation factors are available. Our review identifies the following key topics as being of special interest for future research: the role of intraspecific variation in speciation; the detection of balancing versus directional selection in speciation genetic studies; the timing of fixation of alleles of major versus minor effects during plant speciation; the likelihood of adaptive trait introgression; and the identification and characterization of speciation genes and speciation gene networks.

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    • "Such a time frame may be insufficient for genomewide genetic differentiation among these species to have accumulated, especially at the scale of a relatively small area where interspecific gene flow may have been frequent. Phenotypic novelties, reproductive isolation, and adaptation to environmental conditions do not necessarily depend on large-scale genetic alterations; they can be due to divergence at only a few loci (Wu 2001; Lexer and Widmer 2008; Kane et al. 2009). Finding such relatively small differences within non-model genomes is challenging. "

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    • "Such a time frame may be insufficient for genomewide genetic differentiation among these species to have accumulated, especially at the scale of a relatively small area where interspecific gene flow may have been frequent. Phenotypic novelties, reproductive isolation, and adaptation to environmental conditions do not necessarily depend on large-scale genetic alterations; they can be due to divergence at only a few loci (Wu 2001; Lexer and Widmer 2008; Kane et al. 2009). Finding such relatively small differences within non-model genomes is challenging. "
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    • "Additionally , in outcrossing plant species, postzygotic barriers seem more prevalent than prezygotic ones. Differences in habitat preference result in divergent selection, making ecological speciation a likely process in groups with weak reproductive barriers (Milne et al. 2003; Lexer and Widmer 2008; Minder and Widmer 2008; Lexer et al. 2010; Abadie et al. 2012). "
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