Early Branching Angiosperms

1. Amborella trichopoda (Amborellales, Amborellaceae) is sister to all other angiosperms based on numerous molecular phylogenetic studies.  This plant is found only on the island of New Caledonia. It is dioecious with small unisexual flowers.  Its apocarpous ascidiate (growing like a tube) carpels are not postgenitally fused but sealed by secretion.  This and other primitive features, such as lack of vessels and numerous free perianth parts support its phylogenetic position at the base of angiosperms.
2. The next diverging clade of angiosperms is Nymphaeales (Nymphaeaceae - the water lily family).
3. The next clade contains several small families of woody plants placed in Austrobaileyales.  Taken together the ANITA GRADE is composed of Amborellaceae, Nymphaeaceae, Illiciaceae, Trimeniaceae and Austrobaileyaceae (flower, laminar stamen, carpels joined at their apices by secretions).
4. Relationships among the next groups are not well resolved, hence they are depicted as arising from a polytomy.  The four members of this polytomy are the monocots, magnoliids, Ceratophyllaceae, and the eudicots (the latter clade makes up 75% of all angiosperms).
5. The magnoliid clade includes four clades: Piperales (Piperaceae), Canellales, Laurales, and Magnoliales.  In this class we will focus most upon the latter two.  Some features of these plants are:
   
   • Floral parts spirally arranged
   • Perianth well developed, numerous, free
   • Usually many free stamens
   • Gynoecium usually apocarpous, with carpels generally plicate (folded down middle)
   • Many members with aromatic oils
   • pollen with one pore (monosulcate)
     
     

SIUC / College of Science / Elements of Plant Systematics

URL: http://www.plantbiology.siu.edu/PLB304/FamiliesLecture.html

Last updated: 25-Mar-08 / dln