The genus Sorbus (Maloideae, Rosaceae) in Europe and in North Africa: Morphological analysis and systematics

A multivariate morphometric study of the genus Sorbus, from 127 herbarium specimens in Europe and North Africa and nine populations in Spain, shows that twelve species may be easily recognized in the area: S. in the area: S. torminalis, S. latifolia, S. semiincisa, S. aria, S. intermedia, S. minima, S. sudetica, S. chamaemespilus, S. aucuparia, S. hybrida, S. meinichii and S. domestica. Twenty-seven described taxa were very difficult to discriminate using the standard morphological and statistical methods. Some useful characters are: petiole length, leaf-nerve angle, leaf-tooth length, bud and seed shape, fruit structure, presence of tanniferous-cell groups, large sclereids and starch grains in the fruit. The fruit of S. torminalis has a multi-layered cuticle, not previously reported in Sorbus. We detect-ed tetraploidy in S. torminalis and two other sexuals: S. aria and S. chamaemespilus. The geography and the population structure of taxa in S and C Europe does not permit their reproductive isolation; hence a large number of intermediate forms occur. Considering the difficulty in assessing the reproductive isolation of microspecies and in differentiating them morphologically, the use of a taxonomic species concept is proposed in Sorbus. Finally, a key to the species is provided.