Going with the flow? Diversification of gastropods reflects drainage evolution in Africa

Abstract

Aim The roles of geodynamics, climatic variability and landscape evolution in shaping aquatic biodiversity patterns on the African continent remain poorly understood. We studied the geographical origin and phylogenetic relationships of an Afrotropical freshwater snail genus to examine the role of drainage evolution on diversification and range evolution. The relevance of fish provinces in bio‐regionalization of invertebrates was explored, as well as the evolution of habitat specificity.

Location Africa including Madagascar.

Taxon Lanistes (Gastropoda: Ampullariidae).

Methods Based on a sampling covering the entire geographical range, we reconstructed a fossil‐calibrated multi‐locus molecular phylogeny using maximum likelihood and Bayesian inference approaches. After applying species delimitation methods, we estimated ancestral areas and habitats and examined rates of diversification through time using lineage through time plots.

Results RAxML and MrBayes analyses resulted in highly congruent topologies and a strongly supported phylogeny. Our BEAST analysis indicate that Lanistes probably originated in the Eocene about 50 Ma and the most recent common ancestor (MRCA) of all 23 Lanistes OTUs in our study may have inhabited an area including the Central African and adjacent Lower Guinean biogeographical regions. A steeper increase in species accumulation from the middle Miocene (c. 15 to 10 Ma), followed by a decrease towards the present was found. Sympatry and jump dispersal were the common cladogenetic events and only a single anagenetic dispersal event was detected. The biogeographical analyses further suggest that Madagascar was colonized from East Africa and that the Zambezi River was colonized at least twice independently. Seven species are confined to rivers and three live exclusively in lakes. The estimation of ancestral habitats suggested that the MRCA of all Lanistes probably evolved in a riverine habitat.

Main conclusions The diversification of Lanistes started in the Eocene and occurred at a constant pace apart from a possible climate‐related increase in the Miocene. This study highlights the significance of temporal geographical isolation of river systems and subsequent reconnection in clade diversification and of jump dispersal in range evolution. More comparative analyses across various taxa are needed to obtain a better understanding of African freshwater biodiversity.