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Pair-flowered cymes in the Lamiales: structure, distribution and origin.
1Department of Structural and Functional Botany, Faculty Center of Biodiversity, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.
Annals of Botany
|July 26, 2013
Summary
Pair-flowered cymes (PFCs) are unique to Lamiales and found in Calceolariaceae, Sanango, Gesneriaceae, and Plantaginaceae. Their origin is likely a single synapomorphy, though molecular data suggest multiple origins are possible.
Area of Science:
- Plant evolutionary biology
- Inflorescence morphology
- Systematics of Lamiales
Background:
- Indeterminate thyrses, composed of axillary cymes, are common in Lamiales.
- Two cyme types exist: ordinary cymes and unique pair-flowered cymes (PFCs).
- The distribution, origin, and phylogeny of PFCs remain poorly understood.
Purpose of the Study:
- To investigate the occurrence and diversity of pair-flowered cymes (PFCs) within the Lamiales order.
- To explore the evolutionary origins and phylogenetic implications of PFCs.
Main Methods:
- Systematic screening of Lamiales taxa for the presence of PFCs, ordinary cymes, and single flowers.
- Morphological and developmental analysis of PFCs.
- Phylogenetic analysis incorporating data from related taxa like Peltanthera.
Main Results:
- PFCs exhibit significant morphological and developmental diversity.
- PFCs are found in Calceolariaceae, Sanango, Gesneriaceae, and within specific tribes of Plantaginaceae.
- Evidence suggests PFCs may have originated from paniculate inflorescences, with front flowers as remnants.
Conclusions:
- PFCs are likely a synapomorphy for a clade within Lamiales, with a probable single origin.
- The distribution pattern suggests PFCs may have been lost in parts of the Plantaginaceae.
- Molecular data present ambiguity, allowing for scenarios of single, double, or triple origins depending on phylogenetic interpretations.
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