AUTHOR=Tkach Natalia , Nobis Marcin , Schneider Julia , Becher Hannes , Winterfeld Grit , Jacobs Surrey W. L. , Röser Martin 

TITLE=Molecular Phylogenetics and Micromorphology of Australasian Stipeae (Poaceae, Subfamily Pooideae), and the Interrelation of Whole-Genome Duplication and Evolutionary Radiations in This Grass Tribe

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.630788

DOI=10.3389/fpls.2020.630788

ISSN=1664-462X

ABSTRACT=<p>The mainly Australian grass genus <italic>Austrostipa</italic> (tribe Stipeae) comprising approximately 64 species represents a remarkable example of an evolutionary radiation. To investigate aspects of diversification, macro- and micromorphological variation in this genus, we conducted molecular phylogenetic and scanning electron microscopy (SEM) analyses including representatives from most of <italic>Austrostipa</italic>’s currently accepted subgenera. Because of its taxonomic significance in Stipeae, we studied the lemma epidermal pattern (LEP) in 34 representatives of <italic>Austrostipa.</italic> Plastid DNA variation within <italic>Austrostipa</italic> was low and only few lineages were resolved. Nuclear ITS and <italic>Acc1</italic> yielded comparable groupings of taxa and resolved subgenera <italic>Arbuscula</italic>, <italic>Petaurista</italic>, and <italic>Bambusina</italic> in a common clade and as monophyletic. In most of the <italic>Austrostipa</italic> species studied, the LEP was relatively uniform (typical maize-like), but six species had a modified cellular structure. The species representing subgenera <italic>Lobatae</italic>, <italic>Petaurista</italic>, <italic>Bambusina</italic> as well as <italic>A. muelleri</italic> from subg. <italic>Tuberculatae</italic> were well-separated from all the other species included in the analysis. We suggest recognizing nine subgenera in <italic>Austrostipa</italic> (with number of species): <italic>Arbuscula</italic> (4), <italic>Aulax</italic> (2), <italic>Austrostipa</italic> (36), <italic>Bambusina</italic> (2), <italic>Falcatae</italic> (10), <italic>Lobatae</italic> (5), <italic>Longiaristatae</italic> (2), <italic>Petaurista</italic> (2) and the new subgenus <italic>Paucispiculatae</italic> (1) encompassing <italic>A. muelleri</italic>. Two paralogous sequence copies of <italic>Acc1</italic>, forming two distinct clades, were found in polyploid <italic>Austrostipa</italic> and <italic>Anemanthele</italic>. We found analogous patterns for our samples of <italic>Stipa</italic> s.str. with their <italic>Acc1</italic> clades strongly separated from those of <italic>Austrostipa</italic> and <italic>Anemanthele</italic>. This underlines a previous hypothesis of <xref ref-type="bibr" rid="B129">Tzvelev (1977)</xref> that most extant Stipeae are of hybrid origin. We also prepared an up-to-date survey and reviewed the chromosome number variation for our molecularly studied taxa and the whole tribe Stipeae. The chromosome base number patterns as well as dysploidy and whole-genome duplication events were interpreted in a phylogenetic framework. The rather coherent picture of chromosome number variation underlines the enormous phylogenetic and evolutionary significance of this frequently ignored character.</p>