A plastid tree can bring order to the chaotic generic taxonomy of Rytidosperma Steud. s.l. (Poaceae)

Abstract

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.

Absence of mammals and the evolution of New Zealand grasses

“…Figure 3 shows a simplified version of that tree, with duplicated species pruned and indicating the presence of leaf abscission and distribution in New Zealand. Relationships obtained are congruent with previous estimates of the danthonioid phylogeny [14,15]. The time-calibrated tree of the subfamily, estimated in BEAST and showing 95 per cent highest posterior densities of node ages, is provided in electronic supplementary material, figure S2.…”

“…To take into account phylogenetic and branch-length uncertainty in our analyses, we generated here a set of optimal trees by combining two recently published datasets [14,15]. The final matrix comprised 299 accessions (representing approx.…”

Flowering Plants. Monocots

“…The circumscription of this genus was addressed by Humphreys et al (2010), who show that it is monophyletic in the original sense of Steudel (1853Steudel ( -1854 Annuals or perennials, caespitose, less than 35 cm tall. Inflorescence branches branched.…”

IX. Subfamily Danthonioideae N.P. Barker & H.P. Linder (2001)

“…The circumscription of this genus was addressed by Humphreys et al (2010), who show that it is monophyletic in the original sense of Steudel (1853Steudel ( -1854 …”