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RESEARCH PRODUCT

Genecological and isozyme studies in Senecio vernalis Waldst. & Kit. and S. vulgaris L. var. vulgaris (Asteraceae) from Central Europe and Israel

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Summary Genecological evidence and evidence obtained from an isozyme survey suggest a considerable amount of intraspecific differentiation in Senecio vernalis . Plants of this species from Israel were found to differ strikingly from those of C European (German) origin in most of the traits investigated, e.g., in the possession of pronounced seed dormancy, which seems to be governed by a single gene, a shorter life cycle, lack of rosette growth correlated with stem elongation prior to budding, a larger number of smaller capitula with fewer (disc) florets, and an ephemeral habit with plants only flowering soon after the first winter rains. Both accessions achieved a similar reproductive potential by different means. Electrophoretic analysis of eleven isozyme loci using seven different enzyme systems demonstrated that S. vernalis from Israel and C Europe fit the general pattern that has emerged from plant isozyme studies involving presumed source populations and colonizers derived from these. Thus, the allelic diversity of C European S. vernalis represented a subset of the variation present in S. vernalis from Israel. Historical and ecological factors, interspecific hybridization, and the phylogenetic relationship between the two accessions are discussed as possible causes of the variation in isozyme patterns observed. It is evident that the study of exclusively C European material of S. vernalis by previous workers has concealed phenotypic similarities between Israeli S. vernalis and the closely related S. vulgaris var. vulgaris in speed of development, and probably also photoperiodic response, and several vegetative traits. The presence of pronounced seed dormancy and a strongly abbreviated life cycle in Mediterranean material of both S. vernalis and S. vulgaris var. vulgaris are considered major adaptations to environmental conditions imposed by the Mediterranean climate, leading to similarities in habit. The phylogenetic implications of the present observation of both isozyme and phenotypic variability are briefly discussed.