Conclusions
The plastome analysis provided an informative phylogenetic reconstruction but partial colonization reconstruction of Lobelia columnaris . Overall, three groups are in West-Central Africa.
According to our phylogenomic calibration, the ancestor of L. columnaris arrived in West Central Africa (ca. 1.5 Ma) during the Cameroon line’s youngest volcanoes’ uplift. The Pleistocene climatic oscillations led to the divergence of the Cameroon and Bioko populations into three clades. Likely, South Bioko was forest refugia during the interglacial periods. Here, we show that the biogeographic history ofL. columnaris does not follow the progression of ages of our sky islands.
In more recent times, Bioko’s central depression likely functions as a geographic barrier to further isolate the population groups discovered in our analysis (South Bioko versus North Bioko-Cameroon). Moreover, grazing, burning, and deforestation are threatening Afromontane forest patches with L. columnaris in mainland Cameroon.
Data accessibility We are working the data storage from the plastomes generated in this study. Data will be deposited in GeneBank