Pattern and timing of diversification in the African freshwater fish genus Distichodus (Characiformes: Distichodontidae)

Abstract

Background: Distichodus is a clade of tropical freshwater fishes currently comprising 25 named species distributed continent-wide throughout the Nilo-Sudan and most Sub-Saharan drainages. This study investigates the phylogenetic relationships, timing of diversification, and biogeographic history of the genus from a taxonomically comprehensive mutilocus dataset analyzed using Maximum Likelihood and Bayesian methods of phylogenetic inference, coalescence-based species-tree estimation, divergence time estimation, and inference of geographic range evolution. Results: Analyses of comparative DNA sequence data in a phylogenetic context reveal the existence of two major clades of similar species-level diversity and provide support for the monophyletic status of most sampled species. Biogeographic reconstruction on a time-scaled phylogeny suggest that the origins of the genus date back to the late Oligocene and that current geographic distributions are the result of a Congo Basin origin followed by dispersal and range expansion into adjacent ichthyofaunal provinces at different times during the evolutionary history of the group. Conclusions: We present the most comprehensive phylogenetic, chronological, and biogeographic treatment yet conducted for the genus. The few instances of species paraphyly (D. teugelsi, D. fasciolatus) revealed by the resulting phylogenies are likely a consequence of post-divergence introgressive hybridization and/or incomplete lineage sorting due to recent speciation. Historical biogeographic findings are both in agreement and conflict with previous studies of other continent-wide African freshwater fish genera, suggesting a complex scenario for the assemblage of Africa's continental ichthyofaunal communities.

Following the Mangroves: diversification in the banded lampeye Aplocheilichthys spilauchen (Duméril, 1861) (Cyprinodontiformes: Procatopodidae) along the Atlantic coast of Africa

“…Studies on the evolution of the Congo River drainage (Beadle, 1981;Burke, 1996;Giresse, 2005;Goudie, 2005;Stankiewicz & de Wit, 2006;Runge, 2007), deposition patterns in the Congo deep sea fan (Lavier et al, 2001;Leturmy et al, 2003;Lucazeau et al, 2003;Anka & Séranne, 2004;Anka et al, 2009;Savoye et al, 2009) and freshwater fish diversification in the basin (Goodier et al, 2011;Schwarzer et al, 2011;Alter et al, 2015Alter et al, , 2017Arroyave et al, 2020;Stiassny & Alter, in press) reveal a complex geologic history for the most diverse river basin in Africa. In the western basin, sedimentary studies suggest a protracted history of shifting and intermittent outflow of the Congo River into the Atlantic during the Cenozoic.…”

Cast netting new species: Integrative taxonomy of Distichodus notospilus (Characiformes: Distichodontidae) discovers new species and overlooked areas of endemism in Central Africa

“…Two mitochondrial markers (CO1 and CYTB) and one nuclear marker (MYH6) were examined for specimens collected in Equatorial Guinea and from borrowed comparative material following published methods (Arroyave & Stiassny, 2011;Arroyave et al 2020).Published sequences from D. notospilus, D. maculatus Boulenger, D. kolleri Holly, and D. affinis Günther, were also included in the analyses (Calcagnotto et al 2005;Arroyave & Stiassny, 2011;Sonet et al 2019;Arroyave et al 2020). PartitionFinder2 (Lanfear et al 2017) was used to determine the best model of evolution for each codon position in the datasets.…”

“…Distichodus mbiniensis is readily distinguished from the larger-bodied, higher-scale count Distichodus spp. (group B in Arroyave et al 2020;D. antonii, D. atroventralis, D. fasciolatus, D. lusosso, D. mossambicus, D. sexfasciatus, D. langi, D. rostratus, D. engycephalus, D. kasaiensis, D. ingae, D. polli, D. petersii, D. nefasch, D. brevipinnis, and D. schenga) in having fewer lateral line scales (40-42 versus >60) and in achieving a smaller maximum standard length (<15 cm versus >30 cm).…”

“…This new species is also distinguished from the smaller-bodied, lower-scale count Distichodus spp. (group A in Arroyave et al 2020) in the following ways. Distichodus mbiniensis is distinguished from D. decemmaculatus and D. teugelsi in having two rows of teeth on the lower jaw versus one.…”

“…2 & 3). The published sequences from the Ntem River populations are from previous studies (Arroyave et al 2020;Calcagnotto et al 2005) and these tissues/sequences may need to be verified and additional markers are needed since CO1 was not published from the upper Ntem R. population. Additional specimens from the Ntem River drainage and the smaller coastal rivers in Cameroon are needed to further understand the relationships observed herein.…”