Pleurothallidinae, are we there yet?
Adam Philip Karremans1
1Lankester Botanical Garden, University of Costa Rica, P.O. Box 302-7050 Cartago, Costa Rica.
akarremans@gmail.com
With over 5200 accepted species today, Subtribe Pleurothallidinae is possibly the most species-rich of all orchids. DNA data has proven to be a powerful tool in placing the diverse species of Pleurothallidinae in a less subjective phylogenetic context. Nevertheless, floral similarity due to convergent evolution and floral dissimilarity as a consequence of adaptations to particular pollination systems renders many traditionally used morphological features uninformative.
Identifying morphological traits, either floral or vegetative, that can consistently diagnose diverse species groups is still challenging, but there are several diagnostic features that can be very helpful in placing species. With the availability of molecular data from more than one thousand species of Pleurothallidinae, it is now possible to assess the phylogenetic relationships amongst the vast majority of them, reducing most of the discussion to the interpretations of inclusiveness of generic circumscriptions by diverse authors. These disagreements are likely to persist as they are a consequence of different interpretations of the same evidence rather than the weight or quality of it.
What will hopefully prevail is a consistent use of the adequate phylogenetic framework, therefore how species are related to each other, rather than in what rank they are placed.
Key words: convergence, generic circumscription, Orchidaceae, Neotropics, species-rich.
Pushing the limits: assessing the performance of nrITS for phylogenetic reconstruction and molecular dating of orchids
Cássio van den Berg1
1Universidade Estadual de Feira de Santana. vcassio@uefs.br
The Internal Transcribed Spacer region of nrDNA is the most used DNA region for plant phylogenetic reconstruction. Many orchid phylogenies have been presented including only ITS, or with large ITS phylogenies coupled with reduced combined matrices, due to the fact that ITS generally provides reasonable levels of variation. Some questions were placed on ITS when presented as the only source of phylogenetic data, and there are reports of conflict between nuclear and plastid data. Despite this, there are no assessments of the impact using only ITS data for phylogenetic reconstruction and molecular dating. In this study we evaluate the use of only ITS instead of combined matrices, assessing whether combination of ITS with plastid or other regions indicates topological conflicts that exceed the random expectations due to differences in variation levels. We also assess how ITS performs in estimating molecular dating in relation to combined matrices. The assessment was carried out with matrices from subtribes Pleurothallidinae, Laeliinae, Cymbidieae and Cypripedioideae. The results indicated that the use of secondary structure modelling of ITS1 and ITS2 for alignment and modelling allow the use of ITS over broad phylogenetic distances within Orchidaceae. For molecular dating, ITS performs reasonably well in constrained matrices.
Key words: Internal Transcribed Spacer, modelling, Orchidaceae, phylogenetic conflict, RNA secondary structure.
Funded by: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Morphological diversity of pleurothallid roots Halisson Rafael Kedrovski 1 & Maria das Graças Sajo1
1UNESP-Rio Claro. h.r.kedrovski@hotmail.com
For orchids, when we combine the anatomical characters of roots it is possible to delimit taxa and point out synapomorphies, even if we consider homoplastic features, like those of the velamen.
Different phylogenetic studies enable us to interpret the state and the evolutionary direction of these characters. Neotropical micro-orchids of the subtribe Pleurothallidinae, which encompass 20% of the family’s species (~ 4000), are not all supposed to possess similar roots. We observed that the velamen-exodermis complex of their roots varies morphologically which, together with the cortex and vascular cylinder features, are useful to identify genera. Considering the phylogenetic uncertainties of the group, the root anatomy can add in the characterization of both suprageneric and infrageneric groups and can help in the delimitation of complex genera. Despite the difficulty in obtaining samples (plants are often rare, tiny and difficult to grow), a large effort is necessary to define limits in root morphology within diversified groups, such as Pleurothallidinae.
Key words: Pleurothallidinae, root anatomy, tilosome, velamen-exodermis complex, velamen stripes.
Evolution of Australia’s rich endemic orchid flora in time and space – phylogenomic insights Katharina Nargar1, Natascha Wagner2, Allison Mertin3, Lars Nauheimer4 & Mark Clements5
1Australian Tropical Herbarium & National Research Collections Australia (CSIRO), James Cook University, GPO Box 6811, Cairns, QLD 4878, Australia; 2Dept. of Systematics, Biodiversity and Evolution of Plants, Albrecht Haller Institute for Plant Sciences, Georg August University of Goettingen, Untere Klarspüle 2, 37073 Goettingen, Germany; 3School of Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia; 4Australian Tropical Herbarium, James Cook University, GPO Box 6811, Cairns, QLD 4878, Australia; 5Centre for Australian National Biodiversity Research, GPO Box 1700, Canberra, ACT 2601, Australia Center for Australian National Biodiversity Research, Australia. katharina.nargar@csiro.au
The Australian orchid flora comprises over 1,300 orchid species exhibiting high levels of endemicity with around 90% of species occurring nowhere else. Several orchid lineages underwent extensive diversification on the Australian continent, in particular within tribe Diurideae and subtribe Pterostylidinae – the latter two accounting for over 75% of the country’s orchid diversity.
However, the spatio-temporal evolution of the Australian orchid flora is still poorly understood.
Plastome data for 353 samples was generated via shotgun high-throughput sequencing, representing all genera and major intrageneric lineages within the eleven subtribes in Diurideae and 45% of the species diversity within Pterostylidinae. Phylogenetic tree inferences were carried out in RAxML and MrBayes based on 77 plastid protein coding regions. Divergence time estimations were conducted using fossil and secondary calibration points in BEAST. Key morphological and ecological traits were coded and character state changes traced along the phylogenies under the MK1 model using maximum likelihood. Ancestral range estimations were carried out based on the BEAST chronograms and the dispersal extinction cladogenesis model. This phylogenomic study yielded highly resolved and well supported phylogenetic reconstructions allowing novel insights into the evolution of key morphological and ecological traits and the assembly of the Australian orchid flora.
Key words: Diurideae, historical biogeography, Orchidaceae, phylogenomics, Pterostylidinae.