Wesley E. Higgins

A phylogenetic study of Laeliinae (Orchidaceae) based on combined nuclear and plastid DNA sequences

BACKGROUND AND AIMS 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). KEY 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.

The conservation dilemma

Aunque el Estado de Florida (Estados Unidos) ha adoptado las directrices de la UICN en cuanto a la aplicacion de los criterios de conservacion relacionados a su fauna, existe un vacio en terminos de que ciertas especies pueden ser protegidas a pesar de no encontrarse en la lista de especies amenazadas y recibir algun nivel de proteccion. El Parque Nacional Everglades (Florida) es un habitat critico para un numero de especies raras y otras varias docenas enlistadas como En Peligro o Amenazadas. Sin embargo, un dilema es la interaccion entre especies. En este caso, la mosca endemica Melanagromyza miamensis oviposita sus huevos en la inflorescencia de la orquidea Trichocentrum undulatum. En ella, las larvas se desarrollan gen- eralmente matando al tallo. Este es un ejemplo de la interaccion entre dos especies, una ampliamente dis- tribuida pero localmente incluida bajo la categoria de Criticamente Amenazada (CR) ( T. undulatum) y la especie endemica ( M. miamensis ). De esta manera, se utiliza este ejemplo para demostrar la complejidad en el desarrollo de un plan de manejo.