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Helianthemum oelandicum var. oelandicum is an endemic taxon on the Baltic island of Öland, SE Sweden. Plants can be classified into two morphs: the bristled morph (with bristles and with or without scattered stellate hairs) and the glabrous morph (without bristles and stellate hairs). In crosses between plants assumed to be homozygous for the trait that characterises the phenotypes of the two morphs, offspring in F1 could not be distinguished from the bristled morph. Segregation in F2 did not deviate from the expected 3:1 ratio (bristled morphs/glabrous morphs), indicating one major gene with a dominant allele for the phenotype of the bristled morph and a recessive allele for the phenotype of the glabrous morph. Besides the Mendelian inheritance of presence/absence of hairs, the density of hairs appeared to be further modified by quantitative genes. The frequency of the recessive allele for the phenotype of the glabrous morph varied among local populations and showed a geographical structure, both on local and regional scales. Possible mechanisms behind the spatial variation in indumentum are discussed. [ABSTRACT FROM AUTHOR]

Helianthemum oelandicum var. canescens (Hartm.) Fr. is an endemic taxon with a restricted distribution (less than 10 km) in the southernmost part of the Baltic island of Öland, SE, Sweden. The taxon varies with respect to stellate hairs. Most plants can be classified into two morphs, the stellated morph (with a dense carpet of stellate hairs on the abaxial surface of the leaves) and the bristled morph (without a carpet of stellate hairs). In crosses between plants assumed to be homozygous for the trait that characterises the phenotypes of the two morphs, F1 offspring was indistinguishable from the bristled morph. Segregation in F2 did not deviate from the expected 3:1 ratio (bristled morph/stellated morph), indicating one major gene with a dominant allele for the phenotype of the bristled morph and a recessive allele for the phenotype of the stellated morph. Besides the Mendelian inheritance of the presence/absence of a whitish cover of stellate hairs, the density of hairs appeared to be further modified by quantitative genes. The frequency of the recessive allele for the phenotype of the stellated morph varied among populations and showed a geographical structure. Possible mechanisms behind the spatial variation in indumentum are discussed. [ABSTRACT FROM AUTHOR]

The usefulness of features of leaf hairs in distinguishing subgenera and sections is well documented in both Rhododendron and Solanum. In this analysis of the taxa of Solanum sect. Basarthrum (23 species), and of a sample of closely related taxa from sect. Petota (22 species), it is shown that such features serve to delineate subsectional groups such as series and some species as well. Section Basarthrum has an unexpected diversity of hair types. Although this group has been characterized by 2-celled 'bayonet hairs', more than one half of the taxa in the section bear multicellular 'finger hairs', and 3 species also possess branched hairs. Thus, major rearrangements of the species previously assigned to sect. Basarthrum are indicated or supported by pubescence features. The taxa studied from series Etuberosa and Juglandifolia (both of sect. Petota) show hair types that a) are relatively primitive for the section, and b) show linkage between sects. Petota and Basarthrum. [ABSTRACT FROM AUTHOR]