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Science 17 December 2004:
Vol. 306. no. 5704, p. 1997
DOI: 10.1126/science.306.5704.1997e
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This Week in Science
In many plants, a particular gene system ensures that pollen from one plant is only capable of pollinating non-self plants, thus ensuring outcrossing. However Arabidopsis thaliana can self-pollinate. The genes that would normally enforce self-incompatibility, and thus outcrossing, still exist in Arabidopsis, but only as nonfunctional pseudogenes. Shimizu et al. (p. 2081) show that the sequence diversity found in these alleles through populations of Arabidopsis is considerably lower than found in active, self-incompatibility gene systems. In fact, the sequence diversity is so limited as to suggest the action of positive selection on these pseudogenes. Fixation of this transition to self-pollination has occurred recently, in evolutionary terms, perhaps when Arabidopsis ranges expanded after the Pleistocene. Self-fertility may prove useful to a species when it is expanding its habitat ranges.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
