Palynology and systematics of Ranunculiflorae

Abstract

The pollen morphological variation in the families of the Ranunculiflorae (Berberidaceae, Fumariaceae, Lardizabalaceae Menispermaceae Nelumbonaceae, Papaveraceae and Ranunculaceae) is summarised and discussed in relation to the systematics of the group. The pollen grains are generally dispersed as monads, but permanent tetrads occur in a few instances. Aperture numbers range from one, in spiraperturate pollen of Berberis and some species of Anemone and in the rare monosulcate grains that occur in some individuals of Nelumbo, to three in the majority of species, to many. These tricolpate-derived forms range from zonocolpate to pantocolpate and pantoporate forms. With the exception of some Papaver species, the occurrence of endoapertures appears restricted to Menispermaceae, where they are generally present. The ornamentation is generally punctate to microreticulate, often with spinules or striate to striate-reticulate. The exine stratification is generally tectate-columellate, with a granular infratectum in some taxa, and the endexine is well developed. Pollen grains of Ranunculiflorae exhibit successiformy and spiralization, two of the evolutionary patterns that were first recognised and defined by Van Campo (1967, 1976). These pollen morphological patterns result in a high level of homoplasy (similarity arising through convergent or parallel evolution). Many of the palynological characters are autapomorphic and thus serve to identify distinctive taxa (such as Berberis or Fumaria). Fewer characters can clearly be recognised as synapomorphies at the familial or subfamilial level, especially in the absence of a detailed character analysis integrating palynological and other kinds of evidence. One potentially important character that may not be subject to extensive homoplasy is the occurrence of a compound layer of striae (sensu Nowicke & Skvarla 1982) in contrast to psilate, punctate or microreticulate ornamentation with scabrae or microechinae.