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Pleistocene origin and colonization history of Lobelia columnaris Hook. f. (Campanulaceae: Lobelioideae) across sky islands of West Central Africa
  • Miguel Perez Perez,
  • Wen-Bin Yu
Miguel Perez Perez
Northern Arizona University - Flagstaff Mountain Campus
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Wen-Bin Yu
Xishuangbanna Tropical Botanical Garden
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Abstract

We aimed to infer the phylogenetic relationships of populations of Lobelia columnaris using chloroplast genomes and estimate the divergence time to reconstruct its historical colonization on the sky islands of Bioko and Cameroon. Specifically, we aim to answer the following questions: (1) What is the phylogenetic relationship among Bioko Island and Cameroon populations? (2) Are the older populations found on the older sky islands? (3) Does the colonization history reflect the age of the sky islands? We assembled novel plastomes from 20 individuals of L. columnaris from five mountain systems. The plastome data was explored with phylogenetic analyses using Maximum likelihood and Bayesian Inference. The complete plastome size varied from 164,609 bp to 165,368 bp. The populations of L. columnaris have a monophyletic origin, subdivided into three plastome-geographic clades. The plastid phylogenomic results and age of the sky islands indicate that L. columnaris colonized first along the Cameroon Volcanic Line’s young sky islands. The earliest divergent event (1.54 Ma) split the population in South Bioko from those on the mainland and North Bioko. The population of South Bioko was likely isolated during cold and dry conditions in forest refugia. Presumably, the colonization history occurred during the middle-late Pleistocene from South Bioko’s young sky island to North Bioko and the northern old sky islands in Cameroon. Furthermore, the central depression with lowland forest between North and South Bioko is a current geographic barrier that keeps separate the populations of Bioko from each other and the mainland populations. The Pleistocene climatic oscillations led to the divergence of the Cameroon and Bioko populations into three clades. L. columnaris colonized the older sky island in mainland Cameroon after establishing South Bioko’s younger sky islands. The biogeography history was an inverse progression concerning the age of the Afromontane sky islands.

Peer review status:ACCEPTED

24 Jan 2021Submitted to Ecology and Evolution
27 Jan 2021Submission Checks Completed
27 Jan 2021Assigned to Editor
30 Jan 2021Reviewer(s) Assigned
13 Mar 2021Review(s) Completed, Editorial Evaluation Pending
06 Apr 2021Editorial Decision: Revise Minor
04 Jun 20211st Revision Received
04 Jun 2021Submission Checks Completed
04 Jun 2021Assigned to Editor
04 Jun 2021Review(s) Completed, Editorial Evaluation Pending
04 Jun 2021Reviewer(s) Assigned
16 Jun 2021Editorial Decision: Revise Minor
27 Jul 20212nd Revision Received
28 Jul 2021Submission Checks Completed
28 Jul 2021Assigned to Editor
28 Jul 2021Review(s) Completed, Editorial Evaluation Pending
02 Aug 2021Editorial Decision: Accept