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Cladistic and phenetic analyses of leaf and other morphological characters of Gunnera strongly support monophyly of the genus, with the Saxifragaceae s.str. as the closest sister group. This morphologically based phylogeny provides a more coherent understanding of the evolutionary history of Gunnera than do recent phylogenetic hypotheses based on genetic data sets with Myrothamnaceae as the sister group. Simple, crenate, palinactinodromously veined leaves lacking freely ending veinlets and tricolpate, tectate-perforate pollen with a reticulate exine indicate a shared ancestry. Within the genus Gunnera all six traditionally recognized subgenera are monophyletic, as supported by leaf architectural apomorphies. The monotypic subgenus Ostenigunnera is the sister group to the other five subgenera, which can be divided into two principal lineages. One lineage includes the subgenera Milligania and Misandra, characterized by a prostate stoloniferous habit with small, low-rank leaves and exclusively unisexual flowers, whereas the other lineage includes the subgenera Perpensum, Pseudo-Gunnera, and Panke, all of which possess at least some hermaphroditic flowers and larger, high-rank leaves. When the phylogeny of the subgenera is considered in light of biogeography and the fossil record, a number of cladogenetic events can be explained by continental vicariance in the Late Cretaceous. The African Perpensum became distinct from the other large-leafed lineage with the separation of the African continent ca. 90 Ma. The two small-leafed lineages, the subgenera Milligania and Misandra, split with the separation of New Zealand from Western Gondwana, about 80 Ma. Pseudo-Gunnera became isolated from Panke prior to this time, when Panke fossils occur in North America. Gunnera probably arose out of an early herbaceous radiation of tricolpate eudicots having close affinity to the basal Saxifragaceae, especially the genus Chrysosplenium.
In the 1990s Rubiaceae became a hot spot for systematists, mainly due to the comprehensive treatment of the family by Robbrecht in 1988. Next to the exploration of macromolecular characters to infer the phylogeny, the palynology of Rubiaceae finally received the attention it deserves. This article aims to present a state-of-the-art analysis of the systematic palynology of the family. The range of variation in pollen morphology is wide, and some of the pollen features are not known from other angiosperm taxa; e.g., a looplike or spiral pattern for the position of apertures in pantoaperturate grains. We compiled an online database at the generic level for the major pollen characters and orbicule presence in Rubiaceae. An overview of the variation is presented here and illustrated per character: dispersal unit, pollen size and shape, aperture number, position and type, sexine ornamentation, nexine pattern, and stratification of the sporoderm. The presence/absence and morphological variation of orbicules at the generic level is provided as well. The systematic usefulness of pollen morphology in Rubiaceae is discussed at the (sub)family, tribal, generic, and infraspecific levels, using up-to-date evolutionary hypotheses for the different lineages in the family. The problems and opportunities of coding pollen characters for cladistic analyses are also treated.