Characterizing the Phylogenetic Tree Community Structure of a Protected Tropical Rain Forest Area in Cameroon.

Tropical rain forests, the richest terrestrial ecosystems in biodiversity on Earth are highly threatened by global changes. This
paper aims to infer the mechanisms governing species tree assemblages by characterizing the phylogenetic structure of a
tropical rain forest in a protected area of the Congo Basin, the Dja Faunal Reserve (Cameroon). We re-analyzed a dataset of
11538 individuals belonging to 372 taxa found along nine transects spanning five habitat types. We generated a dated
phylogenetic tree including all sampled taxa to partition the phylogenetic diversity of the nine transects into alpha and beta
components at the level of the transects and of the habitat types. The variation in phylogenetic composition among
transects did not deviate from a random pattern at the scale of the Dja Faunal Reserve, probably due to a common history
and weak environmental variation across the park. This lack of phylogenetic structure combined with an isolation-bydistance
pattern of taxonomic diversity suggests that neutral dispersal limitation is a major driver of community assembly in
the Dja. To assess any lack of sensitivity to the variation in habitat types, we restricted the analyses of transects to the terra
firme primary forest and found results consistent with those of the whole dataset at the level of the transects. Additionally
to previous analyses, we detected a weak but significant phylogenetic turnover among habitat types, suggesting that
species sort in varying environments, even though it is not predominating on the overall phylogenetic structure. Finer
analyses of clades indicated a signal of clustering for species from the Annonaceae family, while species from the
Apocynaceae family indicated overdispersion. These results can contribute to the conservation of the park by improving our
understanding of the processes dictating community assembly in these hyperdiverse but threatened regions of the world.