Rosid Rosid

The complete sequence of Vitis vinifera revealed that the rosid clade derives from a hexaploid ancestor. At present, no analysis of complete genome sequence is available for an asterid, the other large eudicot clade, which includes the economically important species potato, tomato and coffee. To elucidate the genomic history of asterids, we compared the sequence of an 800 kb region of diploid Coffea genome to the orthologous regions of V. vinifera, Populus trichocarpa and Arabidopsis thaliana. We found a very high level of collinearity between around 80 genes of the three rosid species and Coffea. Collinearity comparisons between orthologous and paralogous regions indicates that (1) the Coffea (and consequently all asterids) and rosids share the same hexaploid ancestor; (2) the diploidization process (loss of duplicated and redundant copies from the whole genome duplication) was very advanced in the most recent common ancestor of rosids and asterids. Finally, no additional polyploidization events were detected in the Coffea lineage. Differences in gene loss rates were detected among the three rosid species and linked to the divergence in protein sequences.

The Normapolles complex, characterised by its oblate and triaperturate pollen, constitutes an important and diverse element of many Late Cretaceous and Early Cainozoic floras of the Northern Hemisphere. Based on the dispersed pollen record alone it has been difficult to assess systematic affinities, but relationships with Fagales have been proposed. Over the past twenty years several exquisitely preserved Late Cretaceous reproductive structures with Normapolles type pollen in situ have been described. In this study we provide a summary and new information of these floral structures. Further, a new genus, Dahlgrenianthus, is described from the Late Cretaceous of southern Sweden. The genus includes the type species Dahlgrenianthus suecicus, a number of reproductive structures referred to Dahlgrenianthus sp., and Dahlgrenianthus trigonus (Knobloch et Mai) comb. nov. from the Maastrichtian flora of Walbeck, Germany. Dahlgrenianthus comprises small flowers with pentamerous perianth and androecium and a tricarpellate gynoecium. It is distinguished from all other Normapolles floral structures in its hypogynous floral organisation. All Normapolles floral structures described so far are thought to be related to various members of the core Fagales, but the group is obviously not monophyletic. The stratigraphic range of the Normapolles taxa and other fagalean fossils strongly suggests that all major fagalean lineages were present by the Cenomanian or earlier.

Barbeya is a monotypic genus in the Horn of Africa and adjacent parts of Arabia. It is usually treated as the familyBarbeyaceae and regarded as an aberrant member ofUrticales. Dirachma, with one species on Socotra and one in Somalia, is usually treated as the familyDirachmaceae, inGeraniales, but a position inMalvales has also been suggested. Analyses of molecular data, from bothrbcL andtrnL-F, indicate thatBarbeya andDirachma are closely related inter se as well as toRhamnaceae andElaeagnaceae. In an analysis based on morphologyBarbeya groups withElaeagnaceae, andDirachma withRhamnaceae andUlmaceae. In a combined molecular and morphological analysisBarbeya is the sister group ofElaeagnaceae andDirachma is the sister group of the wholeBarbeya-Elaeagnaceae-Rhamnaceae clade. However, the support for these arrangements is weak and, rather than mergingBarbeyaceae withDirachmaceae as suggested by the molecular analysis or withElaeagnaceae as suggested by the morphological and combined analyses, it seems best to retain bothBarbeyaceae andDirachmaceae in their present circumscriptions, but in both cases in completely new positions in the angiosperm system. The results are compatible with a new circumscription ofRhamnales comprisingRhamnaceae, Elaeagnaceae, Dirachmaceae andBarbeyaceae.