many small daisy-like yellow flower blooms and green leaves in a rocky landscape

The genus Tolpis (Asteraceae-sunflower family) in the Macaronesian islands is being used as a system for studying evolution and diversification on oceanic islands.

These investigations are in collaboration with John Kelly, Mark Mort, and Arnoldo Santos. Results show that sporophytic self-compatiibility (SI) is the common and ancestral condition with variation in the “leakiness” of the system (pseudo-self-compatibility, PSC). There has also been the evolution of true self-compatibility (SC) and associated changes in floral morphology (selfing syndrome) in one species.  Thus, Tolpis is contrary to Baker’s law, namely, that island colonists are generally SC and self-pollinating. One line of investigation is on the association of breeding system with colonization following natural disturbances within the archipelago. Genomic studies with John Kelly on hybrids synthesized in the greenhouse show that breeding system is controlled by one major locus, and investigations are continuing to locate and characterize the S-locus. When this is accomplished, it will be possible to determine whether SC has originated once or multiple times in the Canary Islands, and the role of paucity of compatible mates in limiting seed set in small populations. During numerous expeditions to the Canary Islands the past two decades, hundreds of populations have been observed and material collected for study. One new species was recently described, and several more novelties await description.


  • Dan Crawford