DiscussionPhylogenetic relationship of populations
The ancestor of L. columnaris spread from East Africa via the Congo’s Basin to establish in West-Central Africa approximately 5.5 Ma (Knox & Li 2017). The genealogical relationships among populations ofL. columnaris in the present day were resolved with the analyses of plastomes. However, populations within South Bioko’s subclade do not have high bootstrap values or posterior probabilities, possibly because these populations diverged recently, and the plastome may not be the right marker to show a robust phylogenetic resolution at this fine scale.
We hypothesized that the populations on Bioko shared the same common ancestor. However, our results refute the hypothesis. Our outcome clearly shows an early colonization event in South Bioko. A second divergence separated the populations of North Bioko and Cameroon. According to this result, Bioko’s two populations are not a monophyletic group suggesting that the evolutionary history of the island populations is more complex.
We found a phylogeographic pattern with three clades distributed on the six sky islands. Remarkably, the two clades located in Bioko do not share a more recent common ancestor. The third clade in Cameroon shares a more recent common ancestor with populations in North Bioko.