Adaptive radiation of barbs of the genusLabeobarbus(Cyprinidae) in the East African river

Abstract

Large African barbs of the genus Labeobarbus are widely distributed in African freshwaters, and exhibit profound phenotypic plasticity that could be a prerequisite for adaptive radiation. Using morphological, molecular, and stable isotope analyses, we investigated whether an adaptive radiation has occurred in a riverine assemblage of the L. gananensis complex. This complex is composed of six phenotypically distinct sympatric forms inhabiting the Genale River (Ethiopian highlands, East Africa). Of the six forms, five were divergent in their mouth morphology, corresponding to 'generalized', 'lipped', 'scraping' (two forms) and 'large-mouthed' phenotypes.Stable isotope analysis revealed differences in 15N and 13C among these forms, representing different foraging strategies (omnivorous, scraping and piscivorous). Phylogenetic analysis of two mtDNA markers confirmed the monophyly of L. gananensis, suggesting an intra-riverine radiation. However, the Genale assemblage appears to have originated through a combination of allopatric and sympatric events. Some of the specialized forms within this drainage originated independently from the local generalized forms in three different river regions within local 'miniflocks' composed of two to three sympatric forms. Our study shows that adaptive radiation in rivers can be enhanced by a combination of sympatric speciation and temporal geographic isolation, leading to local sympatric speciation followed by migration.

Infirm effect of phylogeny on morphometric features in a cryptic Gobio species complex

“…Namely, the gms did not showed any congruence with the results of phylogenetic works, whilst the gmb and dbm verified the phylogenetic subdivisions of individuals. Therefore, our results are in correspondence with other notes showing that even low level of phylogenetic differences can manifest in morphological (and functional) features (e.g., Adams et al, 2007;Levin et al, 2019). At the same time, we have to note that the results of three-way PERMANOVA showed (Table 2) that phylogenetic subdivision may have less importance in the formulation of morphometric differences than sexual dimorphism, although this later feature is not so pronounced in this species group (Nowak et al, 2010).…”

Natural toxic impact and thyroid signalling interplay orchestrates riverine adaptive divergence of salmonid fish

“…Nevertheless, the riverine fish flocks have been discovered. The most well‐known examples are the sympatric assemblages of barbs (Levin et al., 2019), cichlids (Pialek et al., 2019; Schwarzer et al., 2011) and mormyrids (Arnegard et al., 2010; Feulner et al., 2008; Sullivan et al., 2002). Compared to the lacustrine flocks, these cases have been dramatically less studied.…”

Association between Labeobarbus spp. (Teleostei: Cyprinidae) and environmental variables in the Luhoho basin (Eastern Congo River basin; DRC)

“…The differences in substrate composition at the localities where L. longidorsalis and L. brauni were found (cobble and pebble vs . boulder: Supporting Information Table S2a,b) provide a novel insight into the understanding of the ecology of Labeobarbus populations with a Var .‐mouth phenotype and illustrates that having a similar Var .‐mouth phenotype does not necessarily imply a similar use of hard rocky substrate types (see also Levin et al ., 2019). In general, nonetheless, the results point to the association of the Var ‐mouth species with some forms of hard rocky substrate.…”

“…In various Ethiopian rivers, Labeobarbus forms with divergent mouth morphologies were found to differ in stable isotope signals, indicating different feeding strategies (Levin et al ., 2019). An additional study uncovered recurrent patterns of ecological diversification in mouth phenotypes in four Ethiopian highland rivers, indicative of parallel adaptive radiation (Levin et al ., 2020).…”