More Smut - Sex-change in Campion Flowers

A while back I posted some pictures of the smut fungus Microbotryum violaceum infecting the anthers of white campion .The flower above is a pink campion - probably a hybrid between white campion Silene latifolia and red campion Silene dioica - whose stamens are also full of the brown fungal spores. Both red and white campions exist as separate male and female plants. This fungus fills the anthers of male plants with its spores which are carried from flower to flower by pollinating insects, but it also brings about a change in the sex of female flowers, so that the female structures are suppressed and appendages called staminodes develop into stamen-like structures that produce the fungal spores and attract insects that are fooled into thinking they are collecting pollen grains. So, when the whole local population has been infected with the sex-changing smut fungus, how do you separate the genuine males from the gender switching females? 

 

 You need to look closely, under the microscope. If the 'stamens' are simply full of fingal spores, like those above, then you are looking a gender-switching female, but.....

 

......  if there are a few large pollen grains amongst the tiny fungal spores, then you are looking at a genuine male plant that was infected after the pollen grains began to develop.

A smutty tale of exploitation and sex-change

You can easily spot campion flowers that have been infected with anther smut fungus Microbotryum violaceum, because the flower petals are stained with the purplish-brown spores of the fungus (top photograph) that multiply in the plant’s stamens – a symptom that is particularly conspicuous in white campion Silene alba. When the anther smut infects its host it proliferates in the stamens, producing tens of thousands of minute, spiny spores (middle photograph) that are then carried from flower to flower by pollinating insects, like the drone fly that’s visiting the red campion Silene dioica flower in the bottom photograph. Hijacking the plant's stamens and pollinators to produce and spread its spores around would be a remarkable adaptation, but this fungus goes one step further in exploiting its host. Campion plants are either male or female and only males have the stamens that the fungus needs for development of its spores, but when the fungal spores infect a female campion - that wouldn’t normally produce stamens in which the fungal spores proliferate - it induces the female plant to change sex and become male, producing stamens where its spores can multiply.