Molecular phylogenetic analyses of nuclear and plastid DNA sequences support dysploid and polyploid chromosome number changes and reticulate evolution in the diversification of Melampodium (Millerieae, Asteraceae).
Chromosome evolution (including polyploidy, dysploidy, and structural changes) as well as hybridization and introgression are recognized as important aspects in plant speciation. A suitable group for investigating the evolutionary role of chromosome number changes and reticulation is the medium-sized genus Melampodium (Millerieae, Asteraceae), which contains several chromosome base numbers (x=9, 10, 11, 12, 14) and a number of polyploid species, including putative allopolyploids. A molecular phylogenetic analysis employing both nuclear (ITS) and plastid (matK) DNA sequences, and including all species of the genus, suggests that chromosome base numbers are predictive of evolutionary lineages within Melampodium. Dysploidy, therefore, has clearly been important during evolution of the group. Reticulate evolution is evident with allopolyploids, which prevail over autopolyploids and several of which are confirmed here for the first time, and also (but less often) on the diploid level. Within sect. Melampodium, the complex pattern of bifurcating phylogenetic structure among diploid taxa overlain by reticulate relationships from allopolyploids has non-trivial implications for intrasectional classification.
Blöch
Cordula
C
Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria. cordula.bloech@univie.ac.at
Weiss-Schneeweiss
Hanna
H
Schneeweiss
Gerald M
GM
Barfuss
Michael H J
MH
Rebernig
Carolin A
CA
Villaseñor
José Luis
JL
Stuessy
Tod F
TF
D019659:Asteraceae / Q000145:classification / Q000235:genetics*; D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D019143:Evolution, Molecular; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D011123:Polyploidy; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer