Niche divergence facilitated by fine‐scale ecological partitioning in a recent cichlid fish adaptive radiation

Abstract

Ecomorphological differentiation is a key feature of adaptive radiations, with a general trend for specialization and niche expansion following divergence. Ecological opportunity afforded by invasion of a new habitat is thought to act as an ecological release, facilitating divergence, and speciation. Here, we investigate trophic adaptive morphology and ecology of an endemic clade of oreochromine cichlid fishes (Alcolapia) that radiated along a herbivorous trophic axis following colonization of an isolated lacustrine environment, and demonstrate phenotype‐environment correlation. Ecological and morphological divergence of the Alcolapia species flock are examined in a phylogenomic context, to infer ecological niche occupation within the radiation. Species divergence is observed in both ecology and morphology, supporting the importance of ecological speciation within the radiation. Comparison with an outgroup taxon reveals large‐scale ecomorphological divergence but shallow genomic differentiation within the Alcolapia adaptive radiation. Ancestral morphological reconstruction suggests lake colonization by a generalist oreochromine phenotype that diverged in Lake Natron to varied herbivorous morphologies akin to specialist herbivores in Lakes Tanganyika and Malawi.

Heterogeneity in food-web interactions of fish in the Mwanza Gulf, Lake Victoria: a quantitative stable isotope study

“…However, there are some caveats, such as the fact that our samples were preserved in (Kaehler & Pakhomov, 2001;Cummings et al, 2010;Syvärante et al, 2011;Ford et al, 2016) and effects are species-specific (Kelly et al, 2006;Syvärante et al, 2008). The C:N ratios of our taxa ranged between 3.1 and 4.4, indicating relatively low lipid contents between taxa (Supplementary Table S1) and thus a minimal lipid effect on d 13 C values.…”

Gene(s) and individual feeding behavior: Exploring eco‐evolutionary dynamics underlying left‐right asymmetry in the scale‐eating cichlid fish Perissodus microlepis

“…Only the δ 13 C, but not the δ 15 N signatures were significantly associated with differentiation between two phenotypes (asymmetric/symmetric). Both groups mainly feed on primary consumers (algae‐eater fishes’ scales or copepods, fishes and insects’ larvae, Nshombo et al., 1985; Takeuchi et al., 2016), resulting in related trophic levels, that are reflected in analogous δ 15 N values, similarly to what was reported for some recently diverged species (e.g., Ford et al., 2016; Malinsky et al., 2015). …”

“…Similar or lower sample sizes had previously been successful in detecting feeding differences in other fish species (e.g., Ford et al., 2016; Kavembe et al., 2016; Manousaki et al., 2013) and the selection of the most extreme specimens contributes to maximize the power of finding differences between groups. The diet during the period over which a tissue is synthesized determines the stable isotope signatures of the tissue.…”

The effects of land use disturbance vary with trophic position in littoral cichlid fish communities from Lake Tanganyika

“…Stable isotope ratios are expressed in parts per mil (‰) with the δ symbol using the equation: δ (‰) = (R sample/R standard − 1) × 1,000, where R = 15 N/ 14 N or 13 C/ 12 C.We aimed to sample 15 individuals of each cichlid species from each site followingFord et al (2016); however, for a third of species at all sites we obtained fewer individuals due to naturally lower density of certain species during sampling, with eight individuals the minimum analysed. Three to 12 individuals of baseline invertebrate species and three replicates of the multispecies algae sample were analysed at each site.…”

“…Isotopic niche is commonly used to compare differences between species ecological niche (e.g Ford et al, 2016;Hata, Shibata, Omori, Kohda, & Hori, 2015;Muschick, Indermaur, & Salzburger, 2012)Ford et al, 2016;Hata, Shibata, Omori, Kohda, & Hori, 2015;Muschick, Indermaur, & Salzburger, 2012)…”