Seed morphology and anatomy and its utility in recognizing subfamilies and tribes of Zingiberaceae.
OBJECTIVE
Recent phylogenetic analyses based on molecular data suggested that the monocot family Zingiberaceae be separated into four subfamilies and four tribes. Robust morphological characters to support these clades are lacking. Seeds were analyzed in a phylogenetic context to test independently the circumscription of clades and to better understand evolution of seed characters within Zingiberaceae.


METHODS
Seventy-five species from three of the four subfamilies were analyzed using synchrotron based x-ray tomographic microscopy (SRXTM) and scored for 39 morphoanatomical characters.


RESULTS
Zingiberaceae seeds are some of the most structurally complex seeds in angiosperms. No single seed character was found to distinguish each subfamily, but combinations of characters were found to differentiate between the subfamilies. Recognition of the tribes based on seeds was possible for Globbeae, but not for Alpinieae, Riedelieae, or Zingibereae, due to considerable variation.


CONCLUSIONS
SRXTM is an excellent, nondestructive tool to capture morphoanatomical variation of seeds and allows for the study of taxa with limited material available. Alpinioideae, Siphonochiloideae, Tamijioideae, and Zingiberoideae are well supported based on both molecular and morphological data, including multiple seed characters. Globbeae are well supported as a distinctive tribe within the Zingiberoideae, but no other tribe could be differentiated using seeds due to considerable homoplasy when compared with currently accepted relationships based on molecular data. Novel seed characters suggest tribal affinities for two currently unplaced Zingiberaceae taxa: Siliquamomum may be related to Riedelieae and Monolophus to Zingibereae, but further work is needed before formal revision of the family.
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109-1005 USA jcbenedi@umich.edu.
John C
JC
Benedict
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109-1005 USA Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109-1079 USA.
Selena Y
SY
Smith
Department of Earth Sciences, Royal Holloway University of London, London, UK, TW20 0EX.
Margaret E
ME
Collinson
Herbarium, Singapore Botanic Gardens, National Parks Board, Singapore 259569.
Jana
J
Leong-Škorničková
Department of Plant and Microbial Biology, Integrative Biology and the University and Jepson Herbaria, University of California, Berkeley, California 94750-2465 USA.
Chelsea D
CD
Specht
Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
Federica
F
Marone
Advanced Photon Source, Argonne National Laboratories, Argonne, Illinois 60439 USA.
Xianghui
X
Xiao
Advanced Light Source, Lawrence Berkeley National Laboratories, Berkeley, California 94720 USA.
Dilworth Y
DY
Parkinson
D005075:Biological Evolution; D012639:Seeds / Q000033:anatomy & histology* / Q000235:genetics; D017356:Synchrotrons; D014056:Tomography, X-Ray; D030521:Zingiberaceae / Q000033:anatomy & histology* / Q000235:genetics
aril; chalaza; embryo; ginger; micropyle; monocotyledon; operculum; seed coat; synchrotron-based x-ray tomographic microscopy (SRXTM); testa