Polyploid evolution in arctic-alpine Draba (Brassicaceae)

• Published in: Sommerfeltia
• Main Author: Brochmann, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 1992
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.2478/som-1992-0003; https://www.sciendo.com/pdf/10.2478/som-1992-0003

Abstract The mainly arctic-alpine genus Draba is well known for its complex morphological and chromosomal vanation. This paper reviews a larger study of Nordic Draba, aimed to provide insights into evolutionary processes that confound taxonomic relationships in the genus. The populations analyzed were referred to 16 currently recognized species of the sections Draba (petals white), Chrysodraba (petals yellow), andDrabella (petals yellow), and investigated using enzyme electrophoresis, restriction site analysis of cpDNA and rDNA, and analysis of chromosome numbers, artificial and natural hybrids, reproductive biology, habitat differentiation, and morphology. Section Draba comprises three diploids and seven polyploids (4x-10x) based on x = 8, sect. Chrysodraba comprises five polyploids (4x-16x) based on x = 8, and sect. Drabella comprises D. crassifolia, which probably is octoploid based on x = 5. Artificial F 1 hybrids were obtained in 19 interspecific combinations. Later-generation hybrids were obtained in seven of these combinations. The genetic data suggest that 1) all polyploids are genetic allopolyploids, i.e., they show disomic inheritance and are highly fixed-heterozygous; 2) several of the polyploids have originated recurrently, some of them even polyphyletically; 3) some of the alloploid populations may have originated from cross-incompatible, sibling species that all belong to a single diploid taxonomic species; 4) interspecific gene flow across chromosome number barriers is possible and probably occurs in natural situations; 5) each of three of the polyploids represents an independent alloploid lineage, whereas sect. Draba and two species of sect. Chrysodraba form an intricate phylogenetic network; 6) some of the polyploids have originated locally, others have migrated repeatedly into the Nordic area; and 7) the phenotypic expression of genes encoding taxonomically important morphological characters does not follow consistent patterns in hybrids; this result may explain the discrepancies between ...