Phylogeny and phylogeography of Altolamprologus: ancient introgression and recent divergence in a rock-dwelling Lake Tanganyika cichlid genus

Stephan Koblmüller,Kristina M Sefc,Lawrence Makasa,Maarten Van Steenberge,Maarten P M Vanhove,Erik Verheyen,Christian Sturmbauer,Bruno Nevado

doi:10.1007/s10750-016-2896-2

Abstract

Stenotopic specialization to a fragmented habitat promotes the evolution of genetic structure. It is not yet clear whether small-scale population structure generally translates into large-scale intraspecific divergence. In the present survey of mitochondrial genetic structure in the Lake Tanganyika endemic Altolamprologus (Teleostei, Cichlidae), a rock-dwelling cichlid genus comprising A. compressiceps and A. calvus, habitat-induced population fragmentation contrasts with weak phylogeographic structure and recent divergence among genetic clades. Low rates of dispersal, perhaps along gastropod shell beds that connect patches of rocky habitat, and periodic secondary contact during lake level fluctuations are apparently sufficient to maintain genetic connectivity within each of the two Altolamprologus species. The picture of genetic cohesion was interrupted by a single highly divergent haplotype clade in A. compressiceps restricted to the northern part of the lake. Comparisons between mitochondrial and nuclear phylogenetic reconstructions suggested that the divergent mitochondrial clade originated from ancient interspecific introgression. Finally, ‘isolation-with-migration’ models indicated that divergence between the two Altolamprologus species was recent (67–142 KYA) and proceeded with little if any gene flow. As in other rock-dwelling cichlids, recent population expansions were inferred in both Altolamprologus species, which may be connected with drastic lake level fluctuations.

Highlights

The genetic structure within a species is often predicted by components of the species’ ecology and life history traits (Wiens & Donoghue, 2004)
77 hayplotypes were detected in 150 samples; 12 were exclusive to A. calvus, 62 to A. compressiceps, 1 to A. sp. ‘‘shell’’ and 2 haplotypes were shared between A. calvus and A. compressiceps
The statistical parsimony network and the Bayesian phylogenetic inference (BI) tree revealed two peculiar features of the phylogenetic relationships among mitochondrial control region haplotypes of Altolamprologus, which had to be explored before enquiring into the phylogeography of Altolamprologus

Summary

Introduction

The genetic structure within a species is often predicted by components of the species’ ecology and life history traits (Wiens & Donoghue, 2004). Young et al, 1996; Row et al, 2010; Kajtoch et al, 2014) This contrast is evident when the different species occur in the same region. In the two East African lakes Malawi and Tanganyika, stenotopic cichlid species inhabiting the discontinuous rocky littoral consistently show remarkable genetic population differentiation, even across very short geographic distances Differentiation is lower and only occurs on a larger geographic scale in less specialized species and species that inhabit the intermediate habitat, i.e. the transition between rocky and sandy habitat surrounding the rocky habitat patches (Koblmuller et al, 2007a, 2009; Sefc et al, 2007; Kotrschal et al, 2012).

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Discussion

Conclusion