Biogeographical and evolutionary aspects of a Guineo-Congolian bushcricket tribe: Revision of the genera Cestromoecha Karsch, 1893 and Poreuomena Brunner von Wattenwyl, 1878, with the description of new species (Orthoptera, Tettigoniidae, Phaneropterinae)

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Abstract

The genera Cestromoecha and Poreuomena of the tribe Poreuomenini in Phaneropterinae are revised and new generic characters are given for both genera, and six new species are described in Poreuomena. The newly described species are P. biaculeata sp. nov., P. eala sp. nov., P. gracilicercata sp. nov., P. ivoriana sp. nov., P. matthaei sp. nov., and P. tshuapa sp. nov. Based on characters defining the two genera, three species so far listed under Cestromoecha are transferred to Poreuomena: P. crassipes Karsch, 1890, P. laeglae (Massa, 2015), and P. magnicerca (Massa, 2013). One species of Cestromoecha, C. mundamensis Karsch, 1896, is synonymised with C. tenuipes (Karsch, 1890) since no morphological differences were detected between the type specimens. Thus, two species remain with Cestromoecha, and Poreuomena now contains 16 species. Morphological closely-related species of Poreuomena suggest rapid speciation in the Congo Basin due to several expansions and shrinkages of the Guineo-Congolian forest belt since the Oligocene. At least two different morphological lineages are discernible. On the other hand the genus Cestromoecha Karsch, 1893 is a species-poor taxon.

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Tectonic uplift and Eastern Africa aridification.

Pierre Sepulchre, Gilles Ramstein, Frédéric Fluteau … (2006)

The history of Eastern African hominids has been linked to a progressive increase of open grassland during the past 8 million years. This trend was explained by global climatic processes, which do not account for the massive uplift of eastern African topography that occurred during this period. Atmosphere and biosphere simulations quantify the role played by these tectonic events. The reduced topographic barrier before 8 million years ago permitted a zonal circulation with associated moisture transport and strong precipitation. Our results suggest that the uplift itself led to a drastic reorganization of atmospheric circulation, engendering the strong aridification and paleoenvironmental changes suggested by the data.

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Palaeobotanical studies from tropical Africa: relevance to the evolution of forest, woodland and savannah biomes.

Thomas Jacobs (2004)

Fossil plants provide data on climate, community composition and structure, all of which are relevant to the definition and recognition of biomes. Macrofossils reflect local vegetation, whereas pollen assemblages sample a larger area. The earliest solid evidence for angiosperm tropical rainforest in Africa is based primarily on Late Eocene to Late Oligocene (ca. 39-26 Myr ago) pollen assemblages from Cameroon, which are rich in forest families. Plant macrofossil assemblages from elsewhere in interior Africa for this time interval are rare, but new work at Chilga in the northwestern Ethiopian Highlands documents forest communities at 28 Myr ago. Initial results indicate botanical affinities with lowland West African forest. The earliest known woodland community in tropical Africa is dated at 46 Myr ago in northern Tanzania, as documented by leaves and fruits from lake deposits. The community around the lake was dominated by caesalpinioid legumes, but included Acacia, for which this, to my knowledge, is the earliest record. This community is structurally similar to modern miombo, although it is different at the generic level. The grass-dominated savannah biome began to expand in the Middle Miocene (16 Myr ago), and became widespread in the Late Miocene (ca. 8 Myr ago), as documented by pollen and carbon isotopes from both West and East Africa.

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Molecular phylogenetics reveal multiple tertiary vicariance origins of the African rain forest trees

Thomas Couvreur, Lars W Chatrou, Marc SM Sosef … (2008)

Background Tropical rain forests are the most diverse terrestrial ecosystems on the planet. How this diversity evolved remains largely unexplained. In Africa, rain forests are situated in two geographically isolated regions: the West-Central Guineo-Congolian region and the coastal and montane regions of East Africa. These regions have strong floristic affinities with each other, suggesting a former connection via an Eocene pan-African rain forest. High levels of endemism observed in both regions have been hypothesized to be the result of either 1) a single break-up followed by a long isolation or 2) multiple fragmentation and reconnection since the Oligocene. To test these hypotheses the evolutionary history of endemic taxa within a rain forest restricted African lineage of the plant family Annonaceae was studied. Molecular phylogenies and divergence dates were estimated using a Bayesian relaxed uncorrelated molecular clock assumption accounting for both calibration and phylogenetic uncertainties. Results Our results provide strong evidence that East African endemic lineages of Annonaceae have multiple origins dated to significantly different times spanning the Oligocene and Miocene epochs. Moreover, these successive origins (c. 33, 16 and 8 million years – Myr) coincide with known periods of aridification and geological activity in Africa that would have recurrently isolated the Guineo-Congolian rain forest from the East African one. All East African taxa were found to have diversified prior to Pleistocene times. Conclusion Molecular phylogenetic dating analyses of this large pan-African clade of Annonaceae unravels an interesting pattern of diversification for rain forest restricted trees co-occurring in West/Central and East African rain forests. Our results suggest that repeated reconnections between the West/Central and East African rain forest blocks allowed for biotic exchange while the break-ups induced speciation via vicariance, enhancing the levels of endemicity. These results provide an explanation for present day distribution patterns and origins of endemicity for African rain forest trees. Moreover, given the pre-Pleistocene origins of all the studied endemic East African genera and species, these results also offer important insights for setting conservation priorities in these highly diversified but threatened ecosystems.