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.).

Floral evolution by simplification in Monanthotaxis (Annonaceae) and hypotheses for pollination system shifts.

Simplification by reduction has occurred many times independently in the floral evolution of angiosperms. These reductions have often been attributed to changes in reproductive biology. In the angiosperm plant family Annonaceae, most species have flowers with six petals, and many stamens and carpels. In the genus Monanthotaxis several deviations from this pattern have been observed, including flowers that contain three petals and three stamens only. New DNA sequences were generated for 42 specimens of Monanthotaxis. Five chloroplast markers and two nuclear markers for 72 out of 94 species of Monanthotaxis were used to reconstruct a phylogeny of the genus, which revealed several well-supported, morphologically distinct clades. The evolution of four quantitative and two qualitative floral characters was mapped onto this phylogeny, demonstrating a reduction in flower size and number of flower parts in Monanthotaxis. A large variation in stamen forms and numbers, strong correlations between petal size, stamen and carpel number, combined with a non-gradual mode of evolution and the sympatric co-occurrence of Monanthotaxis species from different clades suggest that the high diversity in the African rainforest of this genus is caused by switches in pollination systems.

Correlated evolutionary rates across genomic compartments in Annonaceae.

The molecular clock hypothesis is an important concept in biology. Deviations from a constant rate of nucleotide substitution have been found widely among lineages, genomes, genes and individual sites. Phylogenetic research can accommodate for these differences in applying specific models of evolution. Lineage-specific rate heterogeneity however can generate bi- or multimodal distributions of substitution rates across the branches of a tree and this may mislead phylogenetic inferences with currently available models. The plant family Annonaceae is an excellent case to study lineage-specific rate heterogeneity. The two major sister subfamilies, Annonoideae and Malmeoideae, have shown great discrepancies in branch lengths. We used high-throughput sequencing data of 72 genes, 99 spacers and 16 introns from 24 chloroplast genomes and nuclear ribosomal DNA of 23 species to study the molecular rate of evolution in Annonaceae. In all analyses, longer branch lengths and/or higher substitution rates were found for the Annonoideae compared to the Malmeoideae. The Annonaceae had wide variability in chloroplast length, ranging from minimal 175,684bp to 201,723 for Annonoideae and minimal 152,357 to 170,985bp in Malmeoideae, mostly reflecting variation in inverted-repeat length. The Annonoideae showed a higher GC-content in the conserved parts of the chloroplast genome and higher omega (dN/dS)-ratios than the Malmeoideae, which could indicate less stringent purifying selection, a pattern that has been found in groups with small population sizes. This study generates new insights into the processes causing lineage-specific rate heterogeneity, which could lead to improved phylogenetic methods.

A nonet of novel species of Monanthotaxis (Annonaceae) from around Africa.

As part of an ongoing revision of the genus Monanthotaxis Baill. (Annonaceae), nine new species are described and one variety is reinstated to species rank. Two new species from West Africa (Monanthotaxis aquila P.H.Hoekstra, sp. nov. and Monanthotaxis atewensis P.H.Hoekstra, sp. nov.), four new species from Central Africa (Monanthotaxis couvreurii P.H.Hoekstra, sp. nov., Monanthotaxis latistamina P.H.Hoekstra, sp. nov., Monanthotaxis tripetala P.H.Hoekstra, sp. nov. and Monanthotaxis zenkeri P.H.Hoekstra, sp. nov.), one new species from Tanzania (Monanthotaxis filipes P.H.Hoekstra, sp. nov.), one new species from the area around Maputo (Monanthotaxis maputensis P.H.Hoekstra, sp. nov.), one new species from the Comoro Islands (Monanthotaxis komorensis P.H.Hoekstra, sp. nov.) and Monanthotaxis klainei (Engl.) Verdc. var. angustifolia (Boutique) Verdc. is raised to species level leading to the replacement name Monanthotaxis atopostema P.H.Hoekstra, nom. nov. (not Monanthotaxis angustifolia (Exell) Verdc.). Complete descriptions, comparisons with related species, ecological information and IUCN conservation assessments are given for the new species. Five species were classified as critical endangered, two species as endangered, one as vulnerable and one as least concern, warranting the need of further collecting and studying those species.