Selfish Genes and Plant Speciation
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SYNTHESIS PAPER
Selfish Genes and Plant Speciation ˚ gren J. Arvid A
Received: 29 May 2012 / Accepted: 10 December 2012 / Published online: 18 December 2012 Springer Science+Business Media New York 2012
Abstract A key to understand the process of speciation is to uncover the genetic basis of hybrid incompatibilities. Selfish genetic elements (SGEs), DNA sequences that can spread in a population despite being associated with a fitness cost to the individual organism, make up the largest component in many plant genomes, but their role in the genetics of speciation has long been controversial. However, the realization that many organisms have evolved a variety of suppressor mechanisms that reduce the deleterious effects of SGEs has spurred renewed interest in their importance for speciation. The relationship between SGEs and their suppressors often results in strong selection on at least two interacting loci and this arms race therefore creates a situation where SGEs may give rise to hybrid dysgenesis due to Bateson–Dobzhansky–Muller incompatibilities (BDMIs). Here, I argue that examples of SGEs underlying BDMIs may be particularly common among plants compared to other taxa and that a focus on loci involved in genetic conflicts may be especially useful for workers interested in the genetics of plant speciation. I first discuss why the frequent mating system shifts and hybridization events in plants make for a specifically dynamic relationship between SGEs and plant host genomes. I then review some recent empirical observations consistent with SGE-induced speciation in plants. Lastly, I suggest some future directions to test fully the utility of this perspective.
˚ gren (&) J. A. A Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada e-mail: [email protected]
Keywords Selfish genetic elements Speciation Bateson–Dobzhansky–Muller incompatibilities Mating system Molecular evolution
Selfish Genetic Elements as Speciation Genes The existence of selfish genetic elements (SGEs), DNA sequences that gain a transmission advantage relative to the rest of the genome despite having a negative fitness effect on the individual organism, has long been recognized, but their role in eukaryote evolution in general and speciation in particular remains controversial (Doolittle and Sapienza 1980; Orgel and Crick 1980; Hurst and Werren 2001; Burt and Trivers 2006). The suggested implications are multiple, ranging from genome size evolution (Cavalier-Smith ˚ gren and Wright 2011) to disease dynamics (Racey 1977; A and West 2008). There is an ever-growing list of genes known to be involved in causing hybrid incompatibilities (Rieseberg and Blackman 2010 and Maheshwari and Barbash 2011 provide good overviews) and it is well known that these incompatibilities can arise from both natural and sexual selection (Coyne and Orr 2004). Recently, there has been a renewed interest in the idea that SGEs may be a cause of such incompatibilities (e.g. Michalak 2009; Pres
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