1. ¹Netherlands Institute of Ecology, Center for Terrestrial Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands
2. ²Alterra, Center for Ecosystem Studies, PO Box 47, 6700 AA Wageningen, The Netherlands

Correspondence: JMM van Damme, Netherlands Institute of Ecology, Center for Terrestrial Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands. E-mail: j.vandamme@nioo.knaw.nl

Received 21 April 2003; Revised 10 October 2003; Accepted 30 November 2003; Published online 12 May 2004.

Abstract

The mode of inheritance of the male sterility trait is crucial for understanding the evolutionary dynamics of the sexual system gynodioecy, which is the co-occurrence of female and hermaphrodite plants in natural populations. Both cytoplasmic (CMS) and nuclear (restorer) genes are known to be involved. Theoretical models usually assume a limited number of CMS genes with each a single restorer gene, while reality is more complex. In this study, it is shown that in the gynodioecious species Plantago coronopus two new CMS–restorer polymorphisms exist in addition to the two that were already known, which means four CMS–restorer systems at the species level. Furthermore, three CMS types were shown to co-occur within a single population. All new CMS types showed a multilocus system for male fertility restoration, in which both recessive and dominant restorer alleles occur. Our finding of more than two co-occurring CMS–restorer systems each with multiple restorer genes raises the question how this complex of male sterility systems is maintained in natural populations.