Comparative ITS and AFLP analysis of diploid Cardamine (Brassicaceae) taxa from closely related polyploid complexes.
OBJECTIVE
Diploid representatives from the related polyploid complexes of Cardamine amara, C. pratensis and C. raphanifolia (Brassicaceae), were studied to elucidate phylogenetic relationships among the complexes and among the individual taxa included.


METHODS
Two independent molecular data sets were used: nucleotide sequences from the internal transcribed spacers (ITS) of nrDNA, and amplified fragment length polymorphism (AFLP) markers. Seventeen diploid taxa from the studied groups were sampled.


RESULTS
Both ITS and AFLP analyses provided congruent results in inferred relationships, and revealed two main lineages. While the C. amara group, consisting of C. wiedemanniana and four subspecies of C. amara, was resolved as a well-supported monophyletic group, taxa from the C. pratensis and C. tenera groups (the latter representing diploid taxa of the complex of C. raphanifolia) all appeared together in a single clade/cluster with no support for the recognition of either of the groups. Intra-individual polymorphisms and patterns of nucleotide variation in the ITS region in C. uliginosa and C. tenera, together with the distribution of AFLP bands, indicate ancient hybridization and introgression among these Caucasian diploids.


CONCLUSIONS
The lack of supported hierarchical structure suggests that extensive reticulate evolution between these groups, even at the diploid level, has occurred (although an alternative explanation, namely ancestral polymorphism in ITS data, cannot be completely excluded). Several implications for the investigation of the polyploid complexes of concern are drawn. When tracing origins of polyploid taxa, a much more complex scenario should be expected, taking into account all relatives as potential parents, irrespective of the group in which they are classified.
Marhold
Karol
K
Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 14, SK-845 23 Bratislava, Slovak Republic. karol.marhold@savba.sk
Lihová
Judita
J
Perný
Marián
M
Bleeker
Walter
W
D001483:Base Sequence; D005075:Biological Evolution; D019607:Brassicaceae / Q000145:classification* / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000235:genetics*; D004171:Diploidy; D008969:Molecular Sequence Data; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D011123:Polyploidy; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D021903:DNA, Ribosomal Spacer