Phylogenetically informative pollen structures of 'caesalpinioid' pollen (Caesalpinioideae, Cercidoideae, Detarioideae, Dialioideae and Duparquetioideae: Fabaceae)

We provide an overview of phylogenetically useful pollen structures in five out of the new six subfamily classification of the legume family (Fabaceae). A large and diverse range of pollen structures occurs in the five subfamilies under review. These were, until recently, all part of a much larger subfamily Caesalpinioideae, except for the 'mimosoid clade ', previously recognized as subfamily Mimosoideae, but now part of a recircumscribed subfamily Caesalpinioideae. We do not here present any pollen data on subfamily Papilionoideae, and only consider preliminary data for pollen of the 'mimosoid clade '. The most common pollen structures, and those that particularly identify each subfamily, are discussed, compared and illustrated for the five subfamilies: Caesalpinioideae, Cercidoideae, Detarioideae, Dialioideae and Duparquetioideae. Tricolporate pollen with perforate to microreticulate surface ornamentation occurs in at least some species of all the subfamilies under study except Duparquetioideae. The distribution of pollen structural diversity between and within the subfamilies is discussed. The aperture type, pollen-unit, polarity, symmetry, surface ornamentation and grain size of pollen in each subfamily is described and compared. Apertures are found to be more reliable sources of phylogenetic information than surface ornamentation.