TY - JOUR
T1 - Evolution of reproductive structures in grasses (Poaceae) inferred by sister-group comparison with their putative closest living relatives, Ecdeiocoleaceae
AU - Rudall, Paula J.
AU - Stuppy, Wolfgang
AU - Cunniff, Jennifer
AU - Kellogg, Elizabeth A.
AU - Briggs, Barbara G.
PY - 2005/9
Y1 - 2005/9
N2 - Despite much recent activity in the phylogeny and developmental genetics of grasses, the enigmatic homologies of their reproductive structures remain largely unresolved, partly because their highly derived morphology has resulted in a unique associated terminology. Outstanding questions include whether grass lodicules and stamens are derived from a single perianth or stamen whorl, respectively, whether the grass caryopsis is homologous with a nut, and how the scutellum evolved. We investigated the reproductive structures of the putative sister group of grasses, the southwestern Australian family Ecdeiocoleaceae, which includes two genera, Ecdeiocolea and Georgeantha. The zygomorphic arrangement of the four (rather than six) stamens in male flowers of Ecdeiocolea indicates that they may represent three outer stamens plus the adaxial inner stamen. Within Ecdeiocoleaceae, characters such as the highly unusual nucellus structure of Ecdeiocolea are autapomorphic. Sister-group comparisons indicate that some characteristic grass features, notably the scutellum, do not occur in their putative closest relatives and that more data are needed on early-diverging grass genera to resolve these issues. The grass caryopsis could represent one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria, Joinvillea, and Ecdeiocolea.
AB - Despite much recent activity in the phylogeny and developmental genetics of grasses, the enigmatic homologies of their reproductive structures remain largely unresolved, partly because their highly derived morphology has resulted in a unique associated terminology. Outstanding questions include whether grass lodicules and stamens are derived from a single perianth or stamen whorl, respectively, whether the grass caryopsis is homologous with a nut, and how the scutellum evolved. We investigated the reproductive structures of the putative sister group of grasses, the southwestern Australian family Ecdeiocoleaceae, which includes two genera, Ecdeiocolea and Georgeantha. The zygomorphic arrangement of the four (rather than six) stamens in male flowers of Ecdeiocolea indicates that they may represent three outer stamens plus the adaxial inner stamen. Within Ecdeiocoleaceae, characters such as the highly unusual nucellus structure of Ecdeiocolea are autapomorphic. Sister-group comparisons indicate that some characteristic grass features, notably the scutellum, do not occur in their putative closest relatives and that more data are needed on early-diverging grass genera to resolve these issues. The grass caryopsis could represent one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria, Joinvillea, and Ecdeiocolea.
KW - Caryopsis
KW - Ecdeiocolea
KW - Flower
KW - Georgeantha
KW - Grasses
KW - Monocots
KW - Poaceae
KW - Scutellum
UR - http://www.scopus.com/inward/record.url?scp=23944499773&partnerID=8YFLogxK
U2 - 10.3732/ajb.92.9.1432
DO - 10.3732/ajb.92.9.1432
M3 - Article
AN - SCOPUS:23944499773
SN - 0002-9122
VL - 92
SP - 1432
EP - 1443
JO - American Journal of Botany
JF - American Journal of Botany
IS - 9
ER -