East Gondwana ancestry of the sunflower alliance of families

The sunflower alliance of families comprises nearly 10% of all flowering plant species and includes the largest of all plant families, the sunflower family Asteraceae, which has 23,000 species, and the bellflower family Campanulaceae. Both are worldwide in distribution, but the majority of their species occur in the northern hemisphere. Recently it has been shown that a number of small, woody families from the Australian–Southwest Pacific area also belong in this relationship. Here we add yet another such family and present phylogenetic, biogeographic, and chronological analyses elucidating the origin of this large group of plants. We show that the ancestral lineages are confined to Malesia, Australia, New Guinea, and New Zealand and that the sunflower and bellflower families represent phylogenetically derived lineages within a larger group with a Cretaceous and southern-hemisphere, presumably East Gondwana, ancestry. Their highly derived position in the flowering plant phylogeny makes this significant for understanding the evolution of flowering plants in general.

Pollen profile from sediment core KB1, Holzminden, Northern Germany

The Nachtigall clay pit near Holzminden, northern Germany, is located in a subrosional basin filled with 43 m of interglacial, interstadial and stadial deposits adjacent to the Weser River. The succession separates the Older Middle Terrace from the Younger Middle Terrace of the Weser River. Nachtigall core KB1 (1998) mainly contains silt and clay with intercalated peat layers. The layers of fen peat and intercalated humic silt are between 36 and 22.5 m depth. According to palynological studies, the peat layers and some humic silts were deposited during interglacial and interstadial periods marked by forest vegetation, termed Nachtigall 1 and Nachtigall 2. They are subdivided by a stadial, termed Albaxen. The peat of Nachtigall 1 is interrupted twice by silt and clay strata (Allochthonous Unit I, II) which are reworked sediments of older glacial periods, possibly of late Elsterian or early Holsteinian age. The palynological sequences of Nachtigall and Göttingen/Ottostrasse show the same pattern. Moreover, the contemporaneous pollen profiles of Nachtigall and Göttingen/Ottostrasse can be compared with the Velay pollen sequence (France). The Nachtigall core section 36-26.02 m corresponds to Bouchet 2 - Bonnefond - Bouchet 3 in Velay. The profiles of Velay and Nachtigall are independently correlated to the MIS-timescale and correspond to MIS 7c, 7b, and 7a. TIMS 230Th/U-dating shows ages ranging from 227 + 9/-8 to 201 + 15/-13 ka, which are in good agreement with the inferred MIS 7 age.