Ehrhartoideae. --The ehrhartoid grasses (subfamily Ehrhartoideae), as presently classified, comprise the tribes Ehrharteae, Oryzeae, Phyllorachideae and Streptogyneae (Judziewicz & Clark, 2007), although only the first two were placed in this subfamily previously on the basis of molecular sampling (GPWG, 2001). The subfamily comprises 21 genera and 111 species in GrassWorld (Table 2).
The tribe Ehrharteae is an Old World group comprising the four genera Ehrharta Thunb (27 species), Microlaena R.Br. (4 species), Tetrarrhena R.Br. (6 species) and Zotovia. Edgar & Connor (2 species). A taxonomic revision of the group based on phenetics (Willemse, 1982) placed them together in Ehrharta on the basis that “all the characters on which these genera have been delimited against each other are too variable within the genera to be reliable for such delimitations.” Cladistic work based on ITS1, trnL-F and morphological data, was later undertaken on the group and although, from early results, the diversity could be represented by a single lineage (Verboom, Linder & Stock, 1998), later published topologies of the group (Verboom, Linder & Stock 2003) revealed that three of the originally recognized genera (Ehrharta, Tetrarrhena and Zotovia) were resolved as being monophyletic, whereas Microlaena was shown to be polyphyletic. The genus Ehrharta is the largest in the tribe and is almost restricted to the Cape floral kingdom. Tetrarrhena is found only in temperate Australia and Zotovia only in New Zealand. Microlaena, is fairly widespread in Australasia, Asia and the Pacific (and introduced elsewhere) and probably will be taxonomically split because of its polyphyletic composition. Two of the species, M. tasmanica and M. avenacea are nested together with the two species of Zotovia (and also Ehrharta avenacea from Reunion), whereas the type species Microlaena stipoides and the New Zealand endemic M. polynoda form a
sister group to the Tetrarrhena clade.
The tribe Oryzeae, as currently circumscribed , is a distinct and monophyletic lineage (Duistermaat, 1987; Kellogg & Watson, 1993), although it has historically included genera now placed outside the tribe (Duistermaat, 1987; Guo & Ge, 2005). Within the tribe however, the monophyly of some traditional genera has been supported by molecular work, but not others (Ge, 2002, Guo & Ge, 2005). The Oryzeae used to be grouped together with the Ehrharteae as a large rice tribe (Oryzeae sens. lat.), but since their separation by Tateoka (1963) the number of genera recognized in the tribe has varied from 10 to 13. Recent work has demonstrated the existence of two clades, one including the genera Oryza L., Leersia Sw. and Porteresia Tateoka (the Oryzinae) and the remainder of the genera comprising the Zizaniinae, consisting of the genera Zizania L., Luziola Juss., Zizaniopsis Doell & Asch., Chikusichloa Koidzumi, Rhynchorza Baillon, Hygroryza Nees, Potamophila R.Br., Prosphytochloa Schweick. and Maltebrunia Kunth. Within the Oryzinae the genus Leersia is monophyletic, based on the most recent molecular data (Guo & Ge, 2005) as is a clade including Oryza and Porteresia. Within the Zizaniinae three clades are produced – one including Prosphytochloa,
Potamophila and Chikusichloa, the second Rhynchoryza and Zizania and the third Zizaniopsis and Luziola. Hygroryza produced ambiguous results in this analysis and Maltebrunia was not sampled. The Oryzeae is represented geographically in all continents and in some cases apparent close relatives (Potamophila, Prosphytochloa and Chikusichloa) can come from three different continental regions, a distribution difficult to explain. The morphological synapomorphy of the tribe is the one-flowered spikelet consisting of a lemma, palea and two basal bracts, sometimes called glumes but appearing more as expanded pedicel apices (Terrel et al., 2001).
Eh Ehrharteae Or Oryzeae Ph Phyllorachideae St Streptogyneae Zi Zizaniieae
Zi Chikusichloa
Eh Ehrharta
Ph Humbertochloa
Zi Hygroryza
Or Leersia
Zi Luziola
Or Maltebrunia
Eh Microlaena
Or Oryza
Ph Phyllorachis
Or Porteresia
Zi Potamophila
Or Prosphytochloa
Zi Rhynchoryza
St Streptogyna
Suddia
Eh Tetrarrhena
Zi Zizania
Zi Zizaniopsis
Eh Zotovia