Monday, March 20, 2017

[Ichthyology • 2017] Genomewide SNP Data Reveal Cryptic Phylogeographic Structure and Microallopatric Divergence in a Rapids-adapted Clade of Cichlids from the Congo River


Figure 7.  Variation in fin patterning across genetically defined lineages. Top: aquarium-held female and male Teleogramma brichardi.
In panel below (only females shown): (a) 
Teleogramma brichardi, (e) T. gracile, (g) Tobamaorum.  


Abstract

The lower Congo River is a freshwater biodiversity hot spot in Africa characterized by some of the world's largest rapids. However, little is known about the evolutionary forces shaping this diversity, which include numerous endemic fishes. We investigated phylogeographic relationships in Teleogramma, a small clade of rheophilic cichlids, in the context of regional geography and hydrology. Previous studies have been unable to resolve phylogenetic relationships within Teleogramma due to lack of variation in nuclear genes and discrete morphological characters among putative species. To sample more broadly across the genome, we analysed double-digest restriction-associated sequencing (ddRAD) data from 53 individuals across all described species in the genus. We also assessed body shape and mitochondrial variation within and between taxa. Phylogenetic analyses reveal previously unrecognized lineages and instances of microallopatric divergence across as little as ~1.5 km. Species ranges appear to correspond to geographic regions broadly separated by major hydrological and topographic barriers, indicating these features are likely important drivers of diversification. Mitonuclear discordance indicates one or more introgressive hybridization events, but no clear evidence of admixture is present in nuclear genomes, suggesting these events were likely ancient. A survey of female fin patterns hints that previously undetected lineage-specific patterning may be acting to reinforce species cohesion. These analyses highlight the importance of hydrological complexity in generating diversity in certain freshwater systems, as well as the utility of ddRAD-Seq data in understanding diversification processes operating both below and above the species level.


Figure 7.  Variation in fin patterning across genetically defined lineages. At top: aquarium-held female and male Teleogramma brichardi. In panel below (only females shown): (a) Teleogramma brichardi, (b) T. cf. brichardi, (c) T. cf. depressa, (d) T. depressa, (e) T. gracile, (f) T. monogramma, (g) T. obamaorum.   DOI: 10.1111/mec.13973


 S. Elizabeth Alter, Jason Munshi-South and Melanie L. J. Stiassny. 2017. Genomewide SNP Data Reveal Cryptic Phylogeographic Structure and Microallopatric Divergence in a Rapids-adapted Clade of Cichlids from the Congo River. Molecular Ecology. 26(5); 1401–1419. DOI: 10.1111/mec.13973

Water 'Walls' Spur Evolution of New Colorful Fish Species
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