Flora of Cameroon - Annonaceae Vol 45.

Annonaceae is a major pantropical family with 113 genera and about 2550 species. Cameroon is one of the most biodiverse countries in Africa but its flora remains incompletely known. In this volume of the Flora of Cameroon, we describe 166 native taxa representing 163 species in 28 native genera within the family Annonaceae. A total of 22 species (about 13%) are endemic to the country. We provide keys to all native genera, species, and infraspecific taxa. For each species a detailed morphological description and a map of its distribution in Cameroon are provided. Distribution maps and diversity analyses are based on a taxonomically verified database of 2073 collections. Across Africa, Cameroon is a center of diversity for Annonaceae harboring one of the highest numbers of species and genera. For example, Cameroon harbors the highest number of African species for the only pantropical genus of Annonaceae, Xylopia. Annonaceae are found across all 10 administrative regions of Cameroon but diversity is concentrated within the tropical rain forest areas situated in the south and South-West. The areas around Bipindi and Mount Cameroon show the highest levels of diversity, but this is correlated with collection effort. Line drawings and/or photographs accompany most species. One species new to science Uvariopsisetugeana Dagallier & Couvreur sp. nov. is described. We also undertake a number of nomenclatural changes such as lectotypifications, six new synonymies and two new combinations (Uvariaanisotricha (Le Thomas) Couvreur, comb. nov.; Uvariodendronfuscumvar.giganteum (Engl.) Dagallier & Couvreur, comb. nov.).

RésuméLes Annonacées sont une grande famille pantropicale avec 113 genres et 2550 espèces. Le Cameroun est l'un des pays les plus riches en biodiversité d'Afrique mais sa flore reste incomplètement connue. Dans ce volume de la Flore du Cameroun, nous décrivons 166 taxons représentant 163 espèces dans 28 genres au sein de la famille des Annonaceae. Au total, 22 espèces (environ 13%) sont endémiques du pays. Nous fournissons une clé de tous les genres et espèces et des infra-espèces au sein des genres. Pour chaque espèce une description morphologique détaillée et une carte de sa répartition au Cameroun sont fournies. Les cartes de distribution et les analyses de diversité sont basées sur une base de données taxonomiquement vérifiée de 2073 collections. À travers l'Afrique, le Cameroun est un centre de diversité pour les Annonacées abritant l'un des plus grands nombres d'espèces et de genres. Par exemple, le Cameroun abrite le plus grand nombre d'espèces africaines pour le seul genre pantropical d'Annonaceae, Xylopia. Les Annonaceae sont présentent dans les 10 régions du Cameroun, mais la plus grande diversité est concentrée dans les régions abritant la forêt tropicale humide située au sud et au sud-ouest. Les zones autour de Bipindi et du Mont Cameroun présentent les niveaux de diversité les plus élevés, mais cela est corrélé à l'effort de collecte. Des dessins et/ou des photographies accompagnent la plupart des espèces. Une espèce nouvelle pour la science Uvariopsisetugeana Dagalier & Couvreur sp. nov. est décrite. Nous entreprenons également un certain nombre de changements nomenclaturaux tels que des lectotypifications, six nouvelles synonymies et deux nouvelles combinaisons (Uvariaanisotricha (Le Thomas) Couvreur, comb. nov.; Uvariodendronfuscumvar.giganteum (Engl.) Dagalier & Couvreur, comb. nov.).

Individualistic evolutionary responses of Central African rain forest plants to Pleistocene climatic fluctuations.

Understanding the evolutionary dynamics of genetic diversity is fundamental for species conservation in the face of climate change, particularly in hyper-diverse biomes. Species in a region may respond similarly to climate change, leading to comparable evolutionary dynamics, or individualistically, resulting in dissimilar patterns. The second-largest expanse of continuous tropical rain forest (TRF) in the world is found in Central Africa. Here, present-day patterns of genetic structure are thought to be dictated by repeated expansion and contraction of TRFs into and out of refugia during Pleistocene climatic fluctuations. This refugia model implies a common response to past climate change. However, given the unrivalled diversity of TRFs, species could respond differently because of distinct environmental requirements or ecological characteristics. To test this, we generated genome-wide sequence data for >700 individuals of seven codistributed plants from Lower Guinea in Central Africa. We inferred species' evolutionary and demographic histories within a comparative phylogeographic framework. Levels of genetic structure varied among species and emerged primarily during the Pleistocene, but divergence events were rarely concordant. Demographic trends ranged from repeated contraction and expansion to continuous growth. Furthermore, patterns in genetic variation were linked to disparate environmental factors, including climate, soil, and habitat stability. Using a strict refugia model to explain past TRF dynamics is too simplistic. Instead, individualistic evolutionary responses to Pleistocene climatic fluctuations have shaped patterns in genetic diversity. Predicting the future dynamics of TRFs under climate change will be challenging, and more emphasis is needed on species ecology to better conserve TRFs worldwide.

Phylogenomic approaches reveal how climate shapes patterns of genetic diversity in an African rain forest tree species.

The world's second largest expanse of tropical rainforest is in Central Africa, and it harbours enormous species diversity. Population genetic studies have consistently revealed significant structure across Central African rainforest plants. In particular, previous studies have repeatedly demonstrated a north-south genetic discontinuity around the equatorial line, in a continuous expanse of rainforest where a climatic inversion is documented. Here, we took a phylogeographic approach by sequencing 351 nuclear markers in 112 individuals across the distribution of the African rainforest tree species Annickia affinis (Annonaceae). We showed for the first time that the north-south divide is the result of a single, major colonization event across the climatic inversion from an ancestral population located in Gabon. We suggested that differences in ecological niche of populations located on either side of this inversion may have contributed to this phylogenetic discontinuity. We found evidence for inland dispersal, predominantly in northern areas, and variable demographic histories among genetic clusters, indicating that populations responded differently to past climate change. We show how newly developed genomic tools can provide invaluable insights into our understanding of tropical rainforest evolutionary dynamics.