Using genetic analyses to understand population structure and genet assignment of a clonal forest-floor herb

Clonal plants produce genetically identical offspring through vegetative growth. When referring to clonal offspring, a “ramet” refers to a single physiological individual produced by clonal propagation whereas a “genet” refers to a group of ramets that originate from a single seed. Some clonal plant species produce new ramets on the tips of belowground rhizomes, which causes difficulties determining distributions of individual ramets and in assigning these to genets. Not only does this process require excavation of belowground plant organs, it can be incredibly difficult in situations where the elongated rhizomes of ramets from multiple genets are intermingled. Genotyping offers a solution to this problem, using genetic markers to assign ramets to corresponding genets. 

In a recent study published in AoBP, Tsujimoto et al. investigated how ramets belonging to different genets were distributed in a natural population of Carrdamine leucantha in Hokkaido, Japan. This species is characterized by exceptionally long stoloniferous rhizomes, reaching up to 1.2 m long. The rhizomes between mother and daughter ramets become disconnected within 1–2 years, meaning that a single genet can quickly develop into a group of widespread disconnected ramets. Using genome-wide SNP markers, the authors identified 61 genets in the population although there was inequality both in terms of the size of these genets and in their distribution. It is thought that these variations were likely caused by genet age. The authors concluded that RAD-seq can provide data that allows robust genet assignment for species such as C. leucantha. They hope that future work in this area will aid in understanding exactly how large genets become dominant.