Allozymes aid Antirrhinum assignment
One of the functions of taxonomy is to help us understand the evolutionary relationships between organisms. Furthermore, the range of tools available to taxonomists is becoming ever more versatile, especially as different types of molecular analysis can be utilized to investigate relatedness. All this is evident in the paper by Mateu-Andrés and Segarra-Moragues from Valencia and Zaragozo, Spain (pp. 647-655). They have worked on groups of species within the genus Antirrhinum in which the use of morphological characters to assign certain species to sub-generic groups has proved difficult. The authors used a proteomic approach (looking at differences in protein populations) and in particular focused on eight enzymes that are readily assayable in gelo after electrophoresis. The electrophoretic banding patterns exhibited by these enzymes revealed 14 loci (i.e. some of the enzymes were encoded by more than one genetic locus) providing a total of 51 alleles across the range of species and sub-species studied. Based on a detailed analysis of the distribution of the alleles, the authors calculated genetic distances between the species and sub-species and this in turn led to the construction of a dendrogram. The dendrogram clearly demarcates the two groups of species, previously named subsections Streptosepalum and Antirrhinum. The authors were then able to re-assign particular species between the two groups and to lower the rank of one 'species' to that of sub-species. The data have thus thrown light on the evolution and divergence of these groups in the genus Antirrhinum. In respect of speciation, it is noted that all the species studied are inter-fertile but pollinators can distinguish between them. Hybrids are thus rare and, for some pairs of species, this is reinforced by geographical separation. Thus we have a snapshot in the process of speciation: as the authors comment, reproductive isolation leads to gradual divergence until reproductive barriers appear.
Professor J.A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
