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The consensus tree derived by analysis of just the restriction site character set is almost completely resolved except within the PACC clade (there is also a polytomy within the Bambuseae and another within the Agrostideae).
1995) indicated that the trichotomy within the BOP clade in the consensus tree reflects two alternative equally parsimonious structures; in one tree Pooideae and Bambuseae were resolved as sister taxa, with Ehrhartoideae as the sister group of that clade, and in the other Bambuseae and Ehrhartoideae were resolved as sister taxa, with Pooideae as the sister group of that clade.
9) are present among all early-diverging herbaceous lineages just beyond the point of divergence of Anomochloa and Streptochaeta ([ILLUSTRATION FOR FIGURE 3 OMITTED], nodes 4-13), and in Chusquea Kunth of the Bambuseae.
Spikelets with single fertile florets occur in early-diverging lines (Phareae) and in nearly all later-diverging herbaceous lines (Olyreae, Parianeae, Ehrharta, Oryzeae) before the point of divergence of Brachyelytrum, Pooideae, and the PACC clade, and this condition appears to be plesiomorphic in the Bambuseae.
The other two occurrences of "pseudospikelets" are in the Bambuseae, where they are accounted for by independent origins in Bambusa and Guadua [ILLUSTRATION FOR FIGURE 3 OMITTED], or in larger clades that include these genera.
One general interpretation of the spikelet is that it is homologous in most grasses, the exceptions being Streptochaeta, Anomochloa, and some Bambuseae (Clayton, 1990; for alternative interpretations, see Schuster, 1910; Nunez, 1968; Clifford, 1987).
Later reversions to the multiple-flowered condition then might have occurred within Bambuseae, Pooideae, and the PACC clade.
Thus, the trees and character state distributions in the present results lend some support to Clayton's (1990) interpretation of the evolution of the grass spikelet, with the caveat that all multiple-flowered spikelets present in living grasses, in Bambuseae, Pooideae, and the PACC clade, may represent reversions, while the plesiomorphic multiple-flowered spikelet no longer survives.
The inner whorl of stamens was regained in some Bambuseae in either case, and in Ehrhartoideae (under Alternative Topology 2).