A plastid tree can bring order to the chaotic generic taxonomy of Rytidosperma Steud. s.l. (Poaceae).
Rytidosperma s.l., wallaby grasses and allies, is in dire need of a single, unanimously accepted generic taxonomy. Motivated by the desire to establish a generic classification that complies with phylogeny, we investigated how much phylogenetic signal is contained within a plastid (cpDNA) tree, given that the nrDNA tree (ITS) was uninformative and that a phylogenetic hypothesis based on a single genome may not be reliable. We find that the plastid tree is significantly different from a morphological cladogram and show that this is the result of homoplasy in the morphological dataset. Treated individually, several morphological characters fit the plastid tree very well. Similarly, we find a good fit of the plastid tree with ecological and distribution characters and with biogeographical patterns in the Southern Hemisphere. We conclude that a significant level of the species phylogeny is resolved by the plastid tree and are confident it can form a sound basis for a reconsideration of generic limits. None of the currently recognised seven genera in the Rytidosperma clade is monophyletic. Therefore, we propose combining the segregate genera in Australasia within a broadly construed Rytidosperma, including all the species from Australia, New Guinea, New Zealand and South America.
Humphreys
Aelys M
AM
Institute of Systematic Botany, Zollikerstrasse 107, CH-8008 Zurich, Switzerland. aelys.humphreys@systbot.uzh.ch
Pirie
Michael D
MD
Linder
H Peter
HP
D044362:Australasia; D001499:Bayes Theorem; D018742:DNA, Chloroplast / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D017753:Ecosystem; D019143:Evolution, Molecular; D005843:Geography; D008957:Models, Genetic; D010802:Phylogeny; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013020:South America
D018742:DNA, Chloroplast; D018744:DNA, Plant; D004275:DNA, Ribosomal