Three taxa that nested within the PACCAD clade ( Eriachne, Gynerium, and Micraira) were classified as incertae sedis (of uncertain placement). The GPWG also increased taxon sampling over those of previous phylogenetic studies to include representatives of 62 genera, 30 of which fell within a group described under the newly established PACCAD (Panicoideae, Arundinoideae, Chloridoideae, Centothecoideae, Aristidoideae, Danthonioideae) clade. For comparative purposes we will refer to their results for three plastid sequences ( ndhF, rbcL, trnK/matK), and not their eight-dataset analysis, as these did not differ in subfamilial arrangement, or provide further resolution. Subsequent work by the Grass Phylogeny Working Group (GPWG) addressed weak support within and among the grass subfamilies by making use of informative characters in seven molecular datasets along with a morphological dataset. A previous study utilized the plastid gene sequence ndhF, which supported a monophyletic PACC (Panicoideae, Arundinoideae, Chloridoideae, Centothecoideae) clade, as well as indicating the polyphyletic nature of Arundinoideae. The sister group to the BEP clade has been variously defined as the PACC, PACCAD, PACCMAD, or PACMAD clade with different constituent subfamilies. The PACMAD clade is of particular interest in this study because despite its paramount economic and ecological importance, phylogenetic relationships among its major lineages remain uncertain. The current phylogenetic classification of Poaceae includes a deep grade of three lineages: Anomochlooideae, Pharoideae, and Puelioideae, as well as the crown grasses represented by the BEP (Bambusoideae, Ehrhartoideae, Pooideae) and PACMAD (Panicoideae, Aristidoideae, Chloridoideae, Micrairoideae, Arundinoideae, Danthonioideae) clades. Poaceae have been the subject of numerous phylogenetic studies due to their economic and ecological importance, as well as their dominance in major terrestrial biomes.
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