Intraspecific variation and evolutionary trends in Capparis spinosa L. (Capparaceae)

Abstract

In order to investigate the variability of the polymorphic Capparis spinosa L., a comparative study was carried out in Sicily on subsp. spinosa and subsp. rupestris. Autecology, phenology, quantitative morphology, plant architecture and leaf development of several populations were examined. These data reveal a parapatric distribution of the two subspecies and support their present taxonomic treatment. Subsp. spinosa is widespread on clay soils and shows remarkable intrapopulational variation. It is characterized by shortened reproductive and vegetative periods, high shoot growth rate, winter-desiccating shoot system and stipular thorns. Subsp. rupestris, less variable and linked with carbonatic and volcanic outcrops, shows prolonged phenological patterns, slow growth rate, woody habit and caducous stipules. A noteworthy phenotypic convergence with subsp. rupestris was observed in individuals of subsp. spinosa growing in rocky habitats. The evolutionary trends of Capparis spinosa in the Mediterranean region are discussed.