Meadow thistle, Cirsium dissectum

Meadow thistle, Cirsium dissectum is a key species of the threatened marshy grassland habitat. Looking at the genetic patterns in individuals of meadow thistle in Britain and Ireland shows the intricate link between the habitat of the meadow thistle, its genetic diversity and how well it reproduces.

Populations of plants in fragmented landscapes are threatened by declining habitat quality and reductions in genetic diversity. However, the interactions of these major factors are rarely studied together for species conservation. Here we investigated, the interactions between population size, habitat quality, and genetic diversity for meadow thistle.

It was found that smaller populations had lower genetic diversity, and that reduced genetic diversity had a negative impact on seedling survival. Habitat quality also had a large effect on meadow thistle. Sites with tall vegetation, no bare soil and higher nutrient levels had smaller populations of meadow thistle, but flowering was promoted. Flowering was suppressed in heavily grazed sites with short vegetation.

To conserve meadow thistle, site management needs to maintain habitat variety so that meadow thistle can flower, but there is still bare ground available for seedlings to grow. When either seedling survival or flowering is reduced, negative results through reduced genetic diversity and lowered plant survival can be expected. 

This study therefore highlights the importance of considering both conservation genetics and habitat quality in the conservation of plant species.