Historical Biogeography of Sub-Saharan African Spleenworts

Abstract

Aim

Ferns are globally distributed, yet the number of studies examining the historical evolution of African taxa is relatively low. Investigation of the evolution of African fern diversity is critical in order to understand patterns and processes that have global relevance (e.g., the pantropical diversity disparity [PDD] pattern). This study aims to examine when and from where a globally distributed fern lineage arrived in sub-Saharan Africa, to obtain a better understanding of potential processes contributing to patterns of diversity across the region.

Location

Global, sub-Saharan Africa.

Taxon

Asplenium (Aspleniaceae).

Methods

We analysed five loci from 537 Asplenium taxa using a maximum likelihood (IQ-Tree) phylogenetic framework. For age estimation, we performed penalised likelihood as implemented in treePL, and executed a Bayesian analysis using BEAST. Biogeographical analyses were carried out using BioGeoBEARS.

Results

Most dispersals into Africa occurred within the last ~55 myr, with the highest diversity of sub-Saharan African taxa concentrated in two clades, each of which descended from an Asian ancestor. Additional dispersals to sub-Saharan Africa can be found throughout the phylogeny. Lastly, potential cryptic species diversity exists within Asplenium as evidenced by several polyphyletic taxa.

Main Conclusions

We recover multiple dispersals of Asplenium to sub-Saharan Africa, with two major lineages likely diversifying after arrival.