The Genetics of Self-Compatibility and Associated Floral Characters inTolpis(Asteraceae) in the Canary Islands

Abstract

Members of the genus Tolpis (Asteraceae) endemic to the Canary Islands comprise a monophyletic group with the dispersal of one species to the Cape Verde Islands. Most species are self-incompatible or pseudo-self-compatible perennials. However, one species, Tolpis coronopifolia, consists of self-compatible annual plants with several floral features typical of the selfing syndrome. The evolution of self-compatibility and the selfing syndrome was studied by producing synthetic hybrids between self-incompatible/pseudo-self-compatible and self-compatible plants to determine the genetic architecture of breeding system and floral trait differences. There was a correlation between self-compatibility and selfing floral traits in the F2 generation. Self-incompatibility in Tolpis appears to be controlled by a locus of major effect but with modifier loci affecting seed set. Segregation of floral traits indicates that they are controlled by multiple loci. The high molecular similarity between plants with the two breeding systems suggests that divergence of the self-compatible T. coronopifolia from self-incompatible/pseudo-self-compatible ancestors has been recent. The association between breeding system and floral features likely results from pleiotropy or close linkage and may have facilitated the rapid evolution of the morphologically distinct self-compatible T. coronopifolia.