Erik Smets

Palynological characters and their phylogenetic signal in Rubiaceae

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 varíation 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.

The Floral Nectaries of Polygonum s.l. and related genera (Persicarieae and Polygoneae) : Position, Morphological Nature and Semophylesis

Summary A study of the floral nectaries of Polygonum s.l. and related genera revealed that all nectaries are of a receptacular nature (persistent, axial nectaries). Two nectary types, in which the nectariferous zones are in close positional relationship with the stamens, could be distinguished. The Persicarieae have conspicuous nectarsecreting emergences which can be free or variously fused; trichomes or papillae are usually present. Most Polygoneae possess nectarial zones which are not well developed externally; trichomes or papillae are absent or range from few to many. A phylogenetic trend is suggested starting from a Rheum -like ancestor with intrastaminal nectaries, through a Fagopyrum -like ancestor with free nectaries, to the Polygoneae on the one hand and the Persicarieae on the other. This trend is based on the existence of a centrifugal shift of the nectaries.

Intron evolution in a phylogenetic perspective: Divergent trends in the two copies of the duplicated def gene in Impatiens L. (Balsaminaceae)

The history of MADS box genes is well‐known in angiosperms. While duplication events and gene losses occur frequently, gene structure and intron positions are very conserved. We investigated all six introns in a duplicated MADS box gene (deficiens, def) in selected Impatiens taxa, thereby assessing intron features. For the first time, our study provides a comparison of molecular changes in all introns of a gene from a phylogenetic perspective. Interestingly, a uniform pattern of molecular evolution in the introns of each copy was not observed, but intron length increases, decreases, and size retention can be found in each copy. A tendency to accumulate long autapomorphic indels is also present, thus, a longer intron length does not reflect a higher number of parsimony‐informative characters. Substitution rates vary between introns of each gene copy. While four of the six introns of def1 exhibit a change in their substitution rate, five of the six def2 introns maintain their rates throughout the genus albeit at different levels. In MADS box genes several regulatory sequences are found residing in introns. Thus, presence of putative regulatory motifs was investigated. Most of them are not conserved in position and usually present in only one of the gene copies. In addition, the potential for phylogenetic reconstruction of introns in both def copies is shortly discussed.