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

Abstract

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 twoArgyranthemum populations of putative hybrid origin on Tenerife, the Canary Islands, were investigated using chromosomal, morphometric, and fertility analyses of cultivated progeny families and artificial F1 and F2 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 montaneA. broussonetii and the coastalA. frutescens. The montane species was the chloroplast donor in one of the valleys and the coastal species in the other.