Plant 237

Silene dioica (L.) Clairv. (Caryophyllaceae)


Red campion

Female flower of Silene dioica

Red campion, a hairy, short-lived herbaceous perennial, is native throughout western, central and northern Europe. Red campion is dioecious (i.e., separate male and female plants) and, like humans, gender is determined by sex chromosomes; females are XX and males are XY.

The flowers open during the day and are dark pink to red with five petals; each deeply-notched petal narrows to a long point at the base. The gender of red campion plants is easily determined; male flowers have five, yellow stamens sticking up above the petals, whilst female flowers have five prominent white stigmas.

Other than a few minor reports of uses as a folk medicine or providing a splash of colour to damp meadows, roadsides and woodlands, red campion has no direct human uses. Yet, it has attracted the attention of scientists for hundreds of years. The reason for this is that its biology makes it a valuable model organism for studying plant-pollinator and plant-pathogen interactions, sex chromosome evolution and plant speciation.

Red campion is parasitized by a fungal pathogen, in the genus Microbotryum, which causes anther smut in many other members of the carnation family. The pathogen (Microbotryum violaceum), once thought to be a single species, is now known to comprise numerous closely related species that are specialised to different hosts. Microbotryum sterilises red campion flowers; the anthers of male flowers produce fungal spores in place of pollen and female flowers produce spore-bearing anthers. Infected plants are obvious; flower centres are black with soot-like spores (hence the name 'smut'). Spores are transmitted from diseased to healthy plants by pollinating insects, which has led to Microbotryum being described as a 'plant venereal disease'. Consequently, the Silene-Microbotryum is used to study the transmission of sexual diseases, together with their persistence in, and effects on, the regulation of population size.

Red campion is also a model for studying hybridisation. When this species comes into contact with its close relative white campion (Silene latifolia) hybridisation frequently occurs. The product is a pink-flowered campion Silene x hampeana that may also backcross with its parental species producing complex hybrid populations. Despite their ease of hybridisation and their close genetic similarities, the two parental species are morphologically and ecologically distinct; white campion plants flower most prolifically in the evening and are most frequently found in hedgerows, disturbed habitats and field margins. The questions provoked by such observations have evolutionary implications across many different organisms.

Further reading

Minder AM et al. 2007. Genetic structure of hybrid zones between Silene latifolia and Silene dioica (Caryophyllaceae): evidence for introgressive hybridization. Molecular Ecology 12: 2504-2516.

Antonovics, J. (2005) Plant venereal diseases: insights from a messy metaphor. The New Phytologist 165: 71-80.

Stephen Harris