Morphological and ITS sequence divergence between taxa of Cuminia (Lamiaceae), an endemic genus of the Juan Fernandez Islands, Chile

Morphological and ITS sequence divergence were assessed between the two presently recognized taxa of the endemic genus Cuminia (Lamiaceae), on Masatierra of the Juan Fernandez Islands. Morphological studies were based on leaf morphology of 51 individuals. Individuals of C, fernandezia have narrow and lanceolate leaves with cuneate to acute bases and apices, whereas individuals of C. eriantha have broadly ovate leaves with rounded bases and acute to obtuse apices. The two taxa can also be distinguished by the presence of pubescence. Cuminia eriantha has hairs on the leaves, young stems, floral peduncles, calyx, and corolla. Alternatively, C. fernandezia is glabrous except for tuft hairs on the nodes, and hairs on calyx teeth and corolla tubes. The ITS 1 and 2 regions of the five plants of Cuminia sequenced are a total of 451 bp long. All plants have identical ITS-I but pubescent and glabrous plants are consistently different in ITS-2 sequence, revealing 1.3% total sequence divergence between the species. Both morphological and molecular data support the taxonomic recognition of two taxa, and the small but consistent differences appear to justify species status for the two entities. The pubescent populations represent C. eriantha and the glabrous ones are C, fernandezia. It is hypothesized that the species diverged from a common ancestral immigrant to the islands, when Masatierra was much larger and more ecologically diverse than it now is. The two taxa seem to maintain their identities with no evidence of hybridization, even though they often grow in close proximity to one other on the island. Each population consists only of glabrous or pubescent plants, with no mixed population detected.