A phylogenetic study of Laeliinae (Orchidaceae) based on combined nuclear and plastid DNA sequences.
OBJECTIVE
Laeliinae are a neotropical orchid subtribe with approx. 1500 species in 50 genera. In this study, an attempt is made to assess generic alliances based on molecular phylogenetic analysis of DNA sequence data.


METHODS
Six DNA datasets were gathered: plastid trnL intron, trnL-F spacer, matK gene and trnK introns upstream and dowstream from matK and nuclear ITS rDNA. Data were analysed with maximum parsimony (MP) and Bayesian analysis with mixed models (BA).


RESULTS
Although relationships between Laeliinae and outgroups are well supported, within the subtribe sequence variation is low considering the broad taxonomic range covered. Localized incongruence between the ITS and plastid trees was found. A combined tree followed the ITS trees more closely, but the levels of support obtained with MP were low. The Bayesian analysis recovered more well-supported nodes. The trees from combined MP and BA allowed eight generic alliances to be recognized within Laeliinae, all of which show trends in morphological characters but lack unambiguous synapomorphies.


CONCLUSIONS
By using combined plastid and nuclear DNA data in conjunction with mixed-models Bayesian inference, it is possible to delimit smaller groups within Laeliinae and discuss general patterns of pollination and hybridization compatibility. Furthermore, these small groups can now be used for further detailed studies to explain morphological evolution and diversification patterns within the subtribe.
Departamento de Ciências Biológicas, Universidade Estadual de Feira de Santana, 44036-900, Feira de Santana, Bahia, Brazil. vcassio@gmx.de
Cássio
C
van den Berg
Wesley E
WE
Higgins
Robert L
RL
Dressler
W Mark
WM
Whitten
Miguel A
MA
Soto-Arenas
Mark W
MW
Chase
D001483:Base Sequence; D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics*; D030541:Databases, Genetic; D029595:Orchidaceae / Q000235:genetics*; D010802:Phylogeny; D018087:Plastids / Q000145:classification / Q000235:genetics*
D018744:DNA, Plant