Evaluation of some methods for hybrid analysis, exemplified by hybridization in Argyrantheimim (Asteraceae)

Abstract

A grouping of transformations is proposed: 1) “Element transformations”, aimed at changing relations between elements within a single character vector; and 2) “vector transformations”, aimed at changing relations between different character vectors. Logarithmic element transformation seemed suitable for revealing variation in size characters.Principal coordinate analysis (PCO) was appropriate for determination of dimensionality and structural extremes (parentage). Due to polynomial distortions, however, variation in extreme populations was underestimated and variation in intermediate populations exaggerated.A “character index”, the mean of a specimen's ranged characters, is suggested to replace Anderson's hybrid index. Knowledge of parentage and parental maxima, but not of variation in pure parental populations, is required. The character index combined with modified Gay triangles was found suitable for revealing the structure of the material, which showed mainly one‐dimensional variation. The material analysed comprised Argyranthemum broussonetü, A. frutescens, a hybrid swarm and experimental F1 hybrids between these species; and A. sundingü, which was found to be a stabilized hybrid derivative, probably evolved by hybrid speciation with external barriers.