Isozyme differentiation in the endemic genus Argyranthemum (Asteraceae: Anthemideae) in the Macaronesian Islands
Article
Francisco-Ortega, J, Crawford, DJ, Santos-Guerra, A et al. (1996). Isozyme differentiation in the endemic genus Argyranthemum (Asteraceae: Anthemideae) in the Macaronesian Islands
. PLANT SYSTEMATICS AND EVOLUTION, 202(3-4), 137-152. 10.1007/BF00983379
Francisco-Ortega, J, Crawford, DJ, Santos-Guerra, A et al. (1996). Isozyme differentiation in the endemic genus Argyranthemum (Asteraceae: Anthemideae) in the Macaronesian Islands
. PLANT SYSTEMATICS AND EVOLUTION, 202(3-4), 137-152. 10.1007/BF00983379
The genus Argyranthemum (Asteraceae: Anthemideae) comprises 38 taxa and is restricted to the archipelagos of the Canaries, Selvagens, Madeira, and Desertas in the Macaronesian biogeographic region. An electrophoretic study, including 17 enzyme loci and at least one population of each of the described taxa, was carried out. High identity (low distance) values between taxa (mean of 0.893) were obtained despite the old age of the islands, their close proximity to the African continent, and the fact that Argyranthemum is the most species-rich and variable genus in Macaronesia. These results suggest that the genus is monophyletic and that it has evolved very rapidly in these islands. There is little correspondence between taxonomy and neighbor-joining analysis based on Roger's genetic distances, but in several instances populations from the same islands cluster together despite being from different species or even different sections. It is suggested that repeated genetic bottlenecks associated with the founding of new populations during radiation of the genus resulted in lineage sorting of ancestral allozyme polymorphisms. Because every population has a high average identity with all other populations, lineage sorting could result in populations of different taxa being slightly more similar than populations of the same taxon. Gene flow between different species on the same island could account for some populations clustering by island of origin rather than taxonomic disposition. Average allozyme diversity within populations (0.098) is 50% higher than the mean total diversity for species endemic to oceanic islands.
