Premium
Crossing relationships and chromosome numbers of Nordic populations of Draba (Brassicaceae), with emphasis on the D. alpina complex
Author(s) -
Brochmann Christian,
Borgen Liv,
Stedje Brita
Publication year - 1993
Publication title -
nordic journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.333
H-Index - 33
eISSN - 1756-1051
pISSN - 0107-055X
DOI - 10.1111/j.1756-1051.1993.tb00023.x
Subject(s) - biology , botany , ploidy , hybrid , chromosome , brassicaceae , genetics , gene
101 populations of Nordic Draba were investigated for chromosome numbers and crossing relationships. The populations were referred to 16 currently recognized species of Sect. Draba , Sect. Chrysodraba (including the D. alpina complex with D. alpina, D. oxycarpa , and D. corymbosa ), and Sect. Drabella . The chromosome data suggest that all populations and species are homoploid. Three species are diploid, and 13 species are polyploids ranging from tetraploid to 16‐ploid. Draba alpina is decaploid, D. oxycarpa is octoploid, and D. corymbosa is 16‐ploid. The chromosome numbers of D. micropetala (n = 16,4x) and D. adamsii (n = 24,2n = 48, 6x) of Sect. Chrysodraba and D. cinerea (n = 24, 6x) of Sect. Draba were determined for the first time based on Nordic material. The relationships inferred from the crossing data largely agree with those inferred from previously published molecular data, but correspond poorly to relationships inferred from morphology. Inter‐populational F 1 hybrids in D. fladnizensis were entirely sterile, suggesting that this predominantly inbreeding diploid species comprises at least two sibling species, possibly isolated by genic barriers. Sterile to semifertile F 1 hybrids with intermediate chromosome numbers were obtained in 19 interspecific combinations. F 2 hybrids were obtained in seven of these combinations. Both Sect. Chrysodraba and the D. alpina complex are probably polyphyletic. The crossing data suggest that the morphologically very similar polyploids D. alpina (10x) and D. oxycarpa (8x) do not have any diploid progenitors in common, and that Sect. Draba forms an intricate allopolyploid complex that also includes D. alpina and D. corymbosa of Sect. Chrysodraba. Draba corymbosa (16x) is probably an intersectional, polyphyletic alloploid derived from D. alpina (10x) and various hexaploids of Sect. Draba . Crossing data also suggest that D. norvegica (6x) is one of the progenitors of the Nordic endemic D. cacuminum (8x). The phenotypic expression of genes encoding taxonomically important indument characters did not follow consistent patterns in interspecific hybrids. This result may explain the discrepancy between genetic and taxonomic relationships in Nordic Draba , and supports the use of wide taxonomic concepts in this highly reticulate genus.