The impact of multiple molecular and morphological data sets on the phylogenetic reconstruction of subtribe Neurachninae (Poaceae: Panicoideae: Paniceae)

Abstract

The taxonomy of Neurachninane has been unstable, with its member genera consisting of Ancistrachne, Calyptochloa, Cleistochloa, Dimorphochloa, Neurachne, Paraneurachne and Thyridolepis, changing since its original circumscription that comprised only the latter three genera. Recent studies on the phylogeny of Neurachninae have focused primarily on molecular data. We analysed the phylogeny of Neurachninae on the basis of molecular data from seven molecular loci (plastid markers: matK, ndhF, rbcL, rpl16, rpoC2 and trnLF, and ribosomal internal transcribed spacer, ITS) and morphological data from 104 morphological characters, including new taxonomically informative micromorphology of upper paleas. We devised an impact assessment scoring (IAS) protocol to aid selection of a tree for inferring the phylogeny of Neurachninae. Combining morphological and molecular data resulted in a well resolved phylogeny with the highest IAS value. Our findings support reinstatement of subtribe Neurachninae in its original sense, Neurachne muelleri and Dimorphochloa rigida. We show that Ancistrachne, Cleistochloa and Dimorphochloa are not monophyletic and Ancistrachne maidenii, Calyptochloa, Cleistochloa and Dimorphochloa form a new group, the cleistogamy group, united by having unique morphology associated with reproductive dimorphism.

A review of the classification and taxonomic and geographic distribution of cleistogamy in Australian grasses

“…), one oryzoid (Microlaena R.Br.) and four panicoid ('the cleistogamy group') have been recorded with dimorphic axillary CL spikelets (Clifford 1962;Connor and Matthews 1977;Thompson and Fabillo 2021) (Tables 5 and 7). The degree of difference between the terminal and axillary spikelets of the taxa varies from relatively small to distinctive (Table 2).…”

“…Species in 'the cleistogamy group' share unique morphology and the group consists of 11 putative species from Calyptochloa C.E.Hubb., Cleistochloa s.l., Dimorphochloa s.l. and Ancistrachne maidenii (Hamilton) Vickery that all occur predominantly in shady habitats, mostly on shallow sandy soils derived from sandstone (Thompson and Fabillo 2021; Table 3). The species occur within the latitude range 5-36°S, covering tropical, subtropical and temperate climate zones, with only Cleistochloa subjuncea C.E.Hubb.…”

“…Presence of cleistogenes has been used to separate species of Enneapogon (Weiller and Lazarides 2005). CL morphology has also been shown to discriminate groups of genera (Thompson and Fabillo 2021).…”

“…highly modified obligately CL spikelets hidden in basal leaf sheaths or subterranean respectively. Other CL structural peculiarities found in grasses include types of inflorescences (including amphigamy, different inflorescences in different places on the same plant (Chase 1918;Uphof 1938;Campbell et al 1983;Thompson and Fabillo 2021;Fig. 1); CH and CL in different positions in the same terminal inflorescence; synchronicity of the CH and CL flowering; CH and CL on different plants, variations in diaspore morphology and dispersal mechanisms, caryopses (larger size, dormancy, germination) and greater seedling adaptability (Hackel 1906;Laude 1949;Clay 1982Clay , 1983aClay , 1983bCampbell et al 1983;Clay and Antonovics 1985;Clay and Antonovics 1986;Bartholomew 1987;Adkins et al 2002).…”

Cryptachne E.J.Thomps. (Poaceae: Panicoideae: Cleistochloinae), a new genus for Queensland with three new species

“…Cleistogamy is found in c. 3% of grass species and c. 10% of the genera worldwide, and 14% of the species and 30% of genera in Thompson 2021bThompson , 2021cThompson , 2022b. Molecular and morphological datasets generated phylogenetic and phenetic analyses of this eroup (Thompson & Fabillo 2021;Thompson 2021c). Dimorphochloa appears to be not monophyletic based on these initial analyses (Thompson & Fabillo 2021); however, more extensive molecular sampling is still required of extra-Australian taxa, before a final classification can be achieved combining both datasets.…”