Phylogeny of Poaceae tribe Andropogoneae in Australia as a contribution to biological control research on gamba grass ( Andropogon gayanus )

Andropogon gayanus (gamba grass, Poaceae) is a large, tropical grass native to Africa, but introduced as a pasture plant across the tropics worldwide. It is considered invasive in northern Australia, and a research program into the potential of biological control of the species has recently been initiated. Because biological control agents are more likely to pose risks to non-target species closely related to the target weed than to distantly related species, risk management and experimental design in weed biological control require information on the evolutionary relationships of the target weed. Here, we inferred target sequence capture phylogenies of Poaceae tribe Andropogoneae with a focus on Australian lineages of the tribe, combining newly generated and previously published data. Our results place some lineages treated as incertae sedis in the most recent classification of Andropogoneae, including Australian endemics. Clausospicula extensa was retrieved as sister to Chrysopogon, and Spathia neurosa was nested in Dichanthium, but the position of Pseudopogonatherum was inconsistent across our analyses. Our analyses imply that subtribes Apludinae and Anthistiriinae as currently recognised may be non-monophyletic. Only 2 of 25 replicate specimen pairs of the same species failed to group together, confirming a high degree of reproducibility despite differences in bioinformatic approaches between our study and that used for previously published data. The revised phylogeny presented here supports the development of risk assessment plans for biological control and provides additional resources for broader Andropogoneae phylogeny.