Multiple diploid hybrid speciation of the Canary Island endemic Argyranthemum sundingii (Asteraceae)

There are several well-documented examples of multiple hybrid origins of polyploid species. Herein we report the first, to our knowledge, explicit example of a species that most probably has originated recurrently by diploid hybrid speciation. Genetic relationships and stabilization of two Argyranthemum populations of putative hybrid origin on Tenerife, the Canary Islands, were investigated using chromosomal, morphometric, and fertility analyses of cultivated progeny families and artificial F sub(1) and F sub(2) hybrids. These data were compared to a recently published chloroplast DNA phylogeny of the genus, in which the same populations were included. The results suggest that the two populations must be referred to a single species, A. sundingii, which is diploid, fully fertile, genetically stabilized, and occurs in an ecologically intermediate habitat opened by deforestation, and that this species has originated at least twice following local hybridization in two valleys. The same parental species were involved in each origin; the montane A. broussonetii and the coastal A. frutescens. The montane species was the chloroplast donor in one of the valleys and the coastal species in the other.