PLANT LIFE-HISTORY AND DISEASE SUSCEPTIBILITY - THE OCCURRENCE OF USTILAGO-VIOLACEA ON DIFFERENT SPECIES WITHIN THE CARYOPHYLLACEAE

1 Simple models of host-pathogen systems suggest that the ranges of potential hosts for pathogens with no transmission across generations and no free-living stages are likely to be restricted to perennial species, especially longer-lived ones. 2 Data from the empirical literature on the relationship between the presence of anther-smut diseases and host life span in the Caryophyllaceae shows that the distribution of Ustilago violacea among host species within the Caryophyllaceae is closely related to the life span of its host species (the proportion of perennial species on which anther-smuts have been reported is five times higher than the proportion of annuals). 3 The distribution of anther-smuts is also related to host flower morphology and breeding system. There are no reports of anther-smuts from the subfamily Paronychioideae whose members lack petals and are mostly selfing and/or produce cleistogamous flowers. In the two subfamilies for which anther smuts are reported, the percentage of species on which anther-smuts have been recorded is higher in the Silenoideae (where pollinators are primarily Lepidopterans and large bees) than the Alsinoideae (pollinated by flies or other small insects). 4 The results of this study show the importance of considering host and pathogen life histories as well as physiological and biochemical mechanisms in explaining the evolution and ecology of pathogen host ranges.