Appendices & Glossary - Botanical Research Institute of Texas

APPENDIX FOUR
SUBFAMILIAL AND TRIBAL PHYLOGENY/CLASSIFICATION
OF EAST TEXAS POACEAE (GRASS FAMILY)
There has been a tremendous increase in the understanding of grass relationships in recent years, primarily
due to the advent of molecular systematics (e.g., Grass Phylogeny Working Group 2000, 2001).
As a consequence, there have been major changes in grass taxonomy. Many traditional relationships
have been shown to be based on superficial morphological similarities and convergent evolution. On
the other hand, early agrostologists, using limited characteristics, made significant breakthroughs
which are still considered correct today. Currently, the Poaceae is considered to be composed of twelve
subfamilies: Bambusoideae, Anomochlooideae, Pharoideae, Puelioideae, Ehrhartoideae, Centrothecoideae,
Pooideae, Arundinoideae, Danthonioideae, Aristidoideae, Chloridoideae, and Panicoideae
(Grass Phylogeny Working Group 2001), with representatives of nine of these occurring in East Texas.
The subfamilies, tribes, and genera of the 410 species of Poaceae found in East Texas are listed below.
While the relationships among the grass subfamilies are not perfectly known, much progress has
been made in this regard and is now widely available (Grass Phylogeny Working Group 2001;
www.virtualherbarium.org/grass/gpwg/default.htm). Based on multiple molecular data sets and
morphological data (Grass Phylogeny Working Group 2001), the three earliest diverging grass lineages
are the Anomochlooideae, Pharoideae, and Puelioideae, which together account for only 30 species
of grasses. All remaining extant grasses fall into a clade which is composed of two lineages, informally
known as the PACCAD clade and the BEP clade (Grass Phylogeny Working Group 2001) (Fig.
175). The largest group, the PACCAD clade, which consists of the Panicoideae, Arundinoideae,
Chloridoideae, Centothecoideae, Aristidoideae, and Danthonioideae, is now widely recognized as
monophyletic and contains more than half of all species of Poaceae (Kellogg 2003). The other large
group, the BEP clade, is composed of the Bambusoideae, Ehrhartoideae, and Pooideae. Its monophyly is
still an unresolved question, with placement of the Pooideae as sister to the PACCAD clade almost
equally parsimonious (Grass Phylogeny Working Group 2001). All East Texas grass species fall within
the BEP (three subfamilies) and PACCAD (six subfamilies) clades, and all nine subfamilies listed below
are now widely accepted as being monophyletic groups (Grass Phylogeny Working Group 2001). The
subfamilial and tribal placement of the genera given below follows Flora of North America North of
Mexico volumes 24 (Flora of North America Editorial Committee ined.) and 25 (Flora of North
America Editorial Committee 2003) and Grass Phylogeny Working Group (2001).
BEP GRASSES
Subfamily BAMBUSOIDEAE
Tribe Bambuseae
Arundinaria
Bambusa
Phyllostachys
Subfamily EHRHARTOIDEAE
Tribe Oryzeae
Leersia
Luziola
Oryza
Zizania
Zizaniopsis
Tribe Ehrharteae
Ehrhartia
Subfamily POOIDEAE
Tribe Triticeae
Aegilops
Elymus
Hordeum
Secale
Triticum
Tribe Bromeae
Bromus
Tribe Poeae
Briza
Cynosurus
Dactylus
Desmazeria
Festuca
Lolium
Parapholis
Phalaris
Poa
Schlerochloa
Vulpia
Tribe Aveneae (recognized by
Watson & Dalwitz 1992; put in
Poeae by Grass Phylogeny
Working Group 2001)
Agrostis
Aira
Alopecurus
Anthoxanthum
Avena
Cinna
Holcus
Koeleria
Limnodea