The monophyletic tribe Cercideae is one of the earliest branching lineages in Leguminosae, sister to the rest of the family. It is a highly varied and complex group which has undergone many taxonomic re-organisations, and is currently the subject of further systematic studies. The pollen
of the Cercideae has long been known to be diverse and varied, but problematic species and generic delimitations have previously hindered our understanding of the similarities, differences, evolution and taxonomic significance of the various pollen structures found within the tribe. This study
aims to better understand the complexities of the pollen morphological variation by assessing them with regard to recent phylogenetic studies, and also to provide pollen characters that will help to gain more resolution in systematic studies. Approximately 250 pollen samples from tribe Cercideae
were studied using light as well as scanning and transmission electron microscopy, with 58 of those samples taken from 55 species of 12 genera matching those analysed in a recent molecular phylogeny. The distribution of morphological structures is examined by mapping them onto a recently published
molecular phylogenetic tree. Using the molecular phylogeny to show pollen diversity and distribution, we provide an overview of pollen morphology in the Cercideae. The first branching lineages in tribe Cercideae have an unspecialised pollen type, whereas the more variable and distinct pollen
types are found in the more derived lineages, in Schnella, Lasiobema, Phanera and Bauhinia s.str. There is a high degree of specialisation in surface ornamentation, wall structure and aperture type in these groups when compared to other caesalpinioid taxa. The Cercideae
is currently the subject of much research. This overview of pollen structure presents a summary of the distribution of pollen morphological variation, providing data which allows the structural variation in pollen to be compared and contrasted in evolutionary and taxonomic contexts. It also
provides potential autapomorphic and synapomorphic palynological characters of use in phylogenetic analyses and taxonomy.
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Document Type: Research Article
Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, U.K.;, Email: [email protected]
Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, U.K.
Publication date: 28 April 2014
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