Which sex is most sensitive to a sexually transmitted disease?: A case study of the Microbortyum vioalaceum-Silene dioica association
(English)Manuscript (Other academic)
In contrast to the many studies that have addressed whether herbivores discriminate between male and female plants of dioecious plant species, only a few studies have asked whether the two sexes differ in susceptibility to fungal attack. Most of these have dealt with the anther smut Microbotryum violaceum-Silene association and have generally reported a change from male to female biased disease frequencies in parallel to increasing overall disease frequencies. We followed the study system on nine island populations over seven years in a rising Bothnian archipelago. We found an overall pattern that female plants were more diseased than male plants with two exceptions. Disease frequencies were male biased on islands with low disease levels and in one of the seven study years. The change in disease frequencies from male to female bias confirm earlier studies suggesting that the relative contribution of the two components of infection risk, disease encounter and per contact infection probability can vary with population disease level. The change in the proportions of diseased males and females that was observed in one of the study years, followed a year of extreme weather conditions (prolonged drought). Both sexes showed a similar decline in flowering but diseased females decreased more than diseased males. This difference in response can be explained if considering that disease is more resource demanding in females than in males. Except for resources needed for mycelial growth and spore production, in females resources are also needed to restructure their sex expression and produce anthers. Thus in dioecious species traits that are sexually dimorphic are of great importance for understanding the outcome of interactions with natural enemies, including parasitic fungi.
Research subject Ecological Botany
IdentifiersURN: urn:nbn:se:umu:diva-21002OAI: oai:DiVA.org:umu-21002DiVA: diva2:210254