Pollen morphology of selected Brazilian species of Abolboda Humb. et Bonpl. (Xyridaceae): a statistical approach

Previous studies on Abolboda pollen did not conduct statistical analyses of morphological data. Here, the pollen morphology of four Brazilian species and three varieties, represented by 13 herbarium specimens, is described. Pollen grains were treated by 60% lactic acetolysis, measured and photographed under light and scanning electron microscopy. A multivariate analysis was performed for the first time to find possible features that aid the specific and infraspecific delimitation within this genus. Abolboda is characterised by pollen grains in monads that are spheroidal, large to very large sized (59.9 mu m [A. abbreviata] to 158.9 mu m [A. pulchella]), inaperturate and atectate. The nexine is very thick. The spine shape and the width of its base have been considered specific and infraspecific diagnostic features; however, at present, they are not considered consistent characters with a systematic value. The combination of pollen size, nexine thickness, and dimensions of the sexine excrescences ('inverted funnelform shaped' spines, 'obconical shaped' spines, and baculum-like, pilum-like or verruca-like elements) are the most important characteristics at the species level and for grouping the varieties. This study presents informative morphological data useful for future phylogenetic optimisation and contributes to the systematics of the Abolboda genus.