Abstract

Segregation of genetic variation into species is traditionally viewed as the principal unit of evolution while intraspecific hybridization was regarded as a mistake in nature. Nevertheless, intraspecific hybridization is common between many plant species and recent studies have suggested that hybridization may be beneficial to individuals. hybridization is also of interest as it influence species that are interacting with the hybridising species, for example herbivores that need to decide whether or not to forage on hybrids between host plants and non-host plants. To understand how herbivores are influenced by hybridization, and how herbivory influences hybrid plants, I have studied the inheritance of plant resistance characters, foraging preference and performance of herbivores (leaf beetles and voles) and the degree of herbivore damage on pure and hybrid willows. The studied willow species, Salix caprea, S. repens and S. aurita differ in secondary metabolite composition. The results show that both studied groups of secondary metabolites, phenolic glucosides and condensed tannins, are additively inherited in hybrids between S. repens and S. caprea, while condensed tannins are equal in S. caprea, S. aurita and hybrids between the two parental species (Paper I and II). There is no common response of the studied herbivore community. Instead, it seems that specialist herbivores either discriminate against hybrids and non-host parental species or do not separate between hybrids and host parental species. In contrast, generalists usually show either intermediate preference for hybrids, or do not discriminate between hybrids and parental species. One generalist species shows a preference that indicates a breakdown in resistance (Paper II, III, and IV). When adding together the effects of all herbivores, it appears that herbivores inflict more damage to hybrids than parental species (Thesis, paper II and VI).

Keywords

Leaf beetles; voles; performance; preference; plant resistence; phenolics; phenolic glucosides; condensed tannins

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2002, number: 259
ISBN: 91-576-6343-2
Publisher: Swedish University of Agricultural Sciences

Authors' information