Genetic differentiation in the genus Lithops L. (Ruschioideae, Aizoaceae) reveals a high level of convergent evolution and reflects geographic distribution.

Southern Africa is one of the hot spots for plant biodiversity, with ca. 80% of species endemic to this area. Rapid and recent radiations in Southern African plant genera were triggered by fine-scale differences in climate, topography and geology. The genus Lithops (Ruschioideae, Aizoaceae) contains 37 species and is widely distributed in Southern Africa. Species delimitation within the genus is challenging because the limited number of morphological characters in these reduced succulents varies intensely between populations, presumably as adaptations to local geological environments. We analysed phylogenetic relationships within Lithops using non-coding chloroplast DNA (trnS-trnG intergenic spacer), nuclear ribosomal internal transcribed spacer (nrITS) sequences and AFLP data. Genetic variability of the sequence data was very low, but AFLP data detected nine clades within Lithops that do not fit current morphology-based taxonomy. Two of these clades are separated by their distribution on the northern and eastern border of the distribution area, and four clades are found in the Gariep Centre in the estuary of the Orange River. Morphological similarities, especially colour of leaves, evolved repeatedly within the clades, thus we hypothesise that closely related species became adapted to different soil types in a mosaic-like geological environment. One-third of the species are found in the Gariep Centre, characterised by extremely diverse edaphic habitats.

Morphology and nrITS phylogeny of the genus Pinguicula L. (Lentibulariaceae), with special attention to embryo evolution.

The genus Pinguicula (Lentibulariaceae) is unusual within the dicot order Lamiales because of the occurrence of both embryos with two cotyledons and those with just one cotyledon. In order to elucidate the infrageneric relationships and the evolutionary history of the embryo, we analysed (1) the internal transcribed spacers ITS1 and ITS2 of the nuclear ribosomal DNA (nrITS) of 29 Old and New World taxa of Pinguicula, and (2) the morphological and anatomical characters of the seeds. We suggest that the cotyledon number and spermoderm structure were quite unstable in the evolution of Pinguicula. Although basal nodes of the nrITS tree are sensitive to taxon sampling, all tree topologies found in this study imply homoplasy in the cotyledon number.

Genetic diversity in natural and anthropogenic inland populations of salt-tolerant plants: random amplified polymorphic DNA analyses of Aster tripolium L. (Compositae) and Salicornia ramosissima Woods (Chenopodiaceae).

Eight populations of Aster tripolium (Compositae) and six of Salicornia ramosissima (Chenopodiaceae) from inland, naturally salt-contaminated habitats and anthropogenic salt-polluted sites in central Germany (Thuringia, Anhalt-Saxony) were analysed using random amplified polymorphic DNA (RAPD) markers to investigate the patterns of genetic variation. In both species, the genetic diversity observed in the younger, anthropogenic sites caused by potash mines during the last century was found to be not significantly lower than in the older, naturally salt-contaminated habitats. Therefore, it is speculated that the loss of genetic diversity caused by founder effects on the anthropogenic habitats was balanced by successive colonization events, actual gene flow between populations, or the rapid growth of populations on the secondary habitats after colonization. Analyses of molecular variance (amova) of the RAPD markers, neighbour-joining clustering of populations based on Reynolds' co-ancestry distances, and Mantel tests indicate that: (i) anthropogenic habitats were colonized independently; (ii) genetic differentiation among populations of S. ramosissima is more pronounced than in A. tripolium, which is considered to be mainly due to biological differences between the two species; and (iii) the geographical pattern of genetic diversity was considerably modulated by historical events and/or population genetic effects.