*Biology Department, University of York, Heslington, Hork, YOl 5DD.
Biotic environments and the maintenance of sex–some evidence from mutualistic symbioses
Article first published online: 28 JUN 2008
Biological Journal of the Linnean Society
Volume 20, Issue 3, pages 249–276, November 1983
How to Cite
LAW, R. and LEWIS, D. H. (1983), Biotic environments and the maintenance of sex–some evidence from mutualistic symbioses. Biological Journal of the Linnean Society, 20: 249–276. doi: 10.1111/j.1095-8312.1983.tb01876.x
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Accepted for publication July 1982
- Biotic environment;
It has previously been proposed that sex is selected for in organisms living in antagonistic biotic environments. Here, the contrasting case of mutualistic biotic environments is considered. In these environments, it is argued that there should be selection against sex and an accompanying low rate of genetic change. This proposition is tested on mutualistic symbioses with substantial histories of co-evolution in which one partner, the inhabitant, lives partly or wholly inside the other, the exhabitant. This asymmetry between the partners means that inhabitants should exhibit a reduction in sex in comparison to related free-living taxa and a lower rate of genetic change than exhabitants.
The patterns that emerge from an analysis of 10 kinds of mutualistic symbiosis strongly support these predictions. Where adequate information is available, sex is usually reduced in inhabitants in comparison to related free-living taxa, although it remains widespread in exhabitants. Inhabitants are also represented by a much smaller taxonomic diversity than exhabitants. Various alternative reasons for these patterns are considered but it is concluded that they are best explained by the mutualistic environment in which the inhabitants live.