A dated phylogeny and collection records reveal repeated biome shifts in the African genus Coccinia (Cucurbitaceae)

Background: Conservatism in climatic tolerance may limit geographic range expansion and should enhance the effects of habitat fragmentation on population subdivision. Here we study the effects of historical climate change, and the associated habitat fragmentation, on diversification in the mostly sub-Saharan cucurbit genus Coccinia, which has 27 species in a broad range of biota from semi-arid habitats to mist forests. Species limits were inferred from morphology, and nuclear and plastid DNA sequence data, using multiple individuals for the widespread species. Climatic tolerances were assessed from the occurrences of 1189 geo-referenced collections and WorldClim variables. Results: Nuclear and plastid gene trees included 35 or 65 accessions, representing up to 25 species. The data revealed four species groups, one in southern Africa, one in Central and West African rain forest, one widespread but absent from Central and West African rain forest, and one that occurs from East Africa to southern Africa. A few individuals are differently placed in the plastid and nuclear (LFY) trees or contain two ITS sequence types, indicating hybridization. A molecular clock suggests that the diversification of Coccinia began about 6.9 Ma ago, with most of the extant species diversity dating to the Pliocene. Ancestral biome reconstruction reveals six switches between semi-arid habitats, woodland, and forest, and members of several species pairs differ significantly in their tolerance of different precipitation regimes. Conclusions: The most surprising findings of this study are the frequent biome shifts (in a relatively small clade) over just 6 - 7 million years and the limited diversification during and since the Pleistocene. Pleistocene climate oscillations may have been too rapid or too shallow for full reproductive barriers to develop among fragmented populations of Coccinia, which would explain the apparently still ongoing hybridization between certain species. Steeper ecological gradients in East Africa and South Africa appear to have resulted in more advanced allopatric speciation there

The fate of thorium dioxide injected into the coelom of the sedentary polychaete, Sabellastarte Longa (Kinberg)

Zoologica Africana 5(2): 339-34

Holocene Environmental Change at Wonderwerk Cave, South Africa: Insights from Stable Light Isotopes in Ostrich Eggshell

Sparse records and discontinuous and/or poor chronologically resolved data hinder construction of reliable palaeoenvironmental sequences for the interior of South Africa. Wonderwerk Cave occupies a central position in the interior where the Kalahari Thornveld/dry woodland vegetation and generally arid conditions are expected to be sensitive to subtle past climate perturbations, and evidence from this site has been key to forming views on environmental change in the interior. A compilation of existing data including principal component analysis of pollen suggested broad trends, ranging from variably arid and open in the early Holocene to moister conditions from about 7500 to 5000 years, followed by aridity thereafter. In an effort to better establish the nature and timing of shifts from the Late Pleistocene sequence onwards, we analyse carbon and oxygen isotope ratios in a robust sample of ostrich eggshell from Wonderwerk Cave. The resulting data are then placed within a temporal framework established by Bayesian modelling of existing radiocarbon dates and compared against shifts in the Wonderwerk cultural sequence. Several shifts and trends in aridity include an arid to moist shift in layer 4b near 6000 years, coincident with a cultural shift within the Wilton assemblage, and thereafter an aridification trend culminating at about 2000 years with the appearance of the ceramic LSA