Research

Although not widely grown in gardens, Erodium is a popular plant for rock gardens and alpine plantings. When a plant which appeared to be a hybrid was seen growing by enthusiasts, the opportunity was taken to study it further. The name Erodium x variabile A C Leslie was first suggested in 1980, by Dr Alan Leslie at the RHS, for plants found to be intermediate in character between E. corsicum Léman and E. reichardii (Murray) DC. These had been noticed in cultivation for some time. Erodium corsicum and E. reichardii are low-growing perennials from the Mediterranean, with E. x variabile being intermediate between them, particularly with respect to leaf shape and growth form.

Since the hybrid was described however, some alpine enthusiasts have doubted its existence. Attempts to produce it deliberately failed, leading some to believe that the plants were merely selected forms of either reputed parental species. This led to inconsistency and confusion in the styling of the names. As the morphological evidence for hybrid origin was very strong, the RHS's Advisory Panel on Nomenclature and Taxonomy were instrumental in instigating research into the plants genetic material (DNA), to see whether its existence could be proven.

A joint venture was established between the Botany Departments of the RHS and the University of Reading to ascertain whether the parental DNA sequences could be distinguished. The nuclear (ITS) and chloroplast (TrnL-F) genomes were studied for the E. corsicum/E. reichardii group and its cultivars. Plant chloroplasts contain DNA, and are usually inherited from the female parent. In a pure breeding species, both parents would have the same chloroplast type. However where two species hybridise, the female parent can be detected even when it is not known which was the seed-producing plant. By contrast, nuclear DNA can be inherited from either parent, but for the region studied, the male parent has been shown to dominate.

The DNA sequences of Erodium corsicum and E. reichardii showed consistent differences in both regions studied. Chloroplast DNA sequences showed Erodium corsicum to be the female, seed parent of E. x variabile. Nuclear DNA sequences showed Erodium reichardii to be the male, pollen parent of E. x variabile.

The differing inheritance of the DNA sequences supports the hybrid origin of E. x variabile from E. corsicum and E. reichardii. When combined with the morphological differences, this provides ample support for the use of the name Erodium x variabile. This will help to bring stability to the names of these Erodium and the affiliation of the cultivar names.

Back to Introduction to research