title: Foraging environment determines the genetic architecture and evolutionary potential of trophic morphology in cichlid fishes.
abstract: Phenotypic plasticity allows organisms to change their phenotype in response to shifts in the environment. While a central topic in current discussions of evolutionary potential, a comprehensive understanding of the genetic underpinnings of plasticity is lacking in systems undergoing adaptive diversification. Here, we investigate the genetic basis of phenotypic plasticity in a textbook adaptive radiation, Lake Malawi cichlid fishes. Specifically, we crossed two divergent species to generate an F3hybrid mapping population. At early juvenile stages, hybrid families were split and reared in alternate foraging environments that mimicked benthic/scraping or limnetic/sucking modes of feeding. These alternate treatments produced a variation in morphology that was broadly similar to the major axis of divergence among Malawi cichlids, providing support for the flexible stem theory of adaptive radiation. Next, we found that the genetic architecture of several morphological traits was highly sensitive to the environment. In particular, of 22 significant quantitative trait loci (QTL), only one was shared between the environments. In addition, we identified QTL acting across environments with alternate alleles being differentially sensitive to the environment. Thus, our data suggest that while plasticity is largely determined by loci specific to a given environment, it may also be influenced by loci operating across environments. Finally, our mapping data provide evidence for the evolution of plasticity via genetic assimilation at an important regulatory locus, ptch1. In all, our data address long-standing discussions about the genetic basis and evolution of plasticity. They also underscore the importance of the environment in affecting developmental outcomes, genetic architectures, morphological diversity and evolutionary potential.
authors: Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
authors: Kevin J
authors: KJ
authors: Parsons
authors: Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA, 01003, USA.
authors: Moira
authors: M
authors: Concannon
authors: Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA, 01003, USA.
authors: Dina
authors: D
authors: Navon
authors: Department of Biology, University of Massachusetts, Amherst, MA, 01003, USA.
authors: Jason
authors: J
authors: Wang
authors: Department of Biology, University of Massachusetts, Amherst, MA, 01003, USA.
authors: Ilene
authors: I
authors: Ea
authors: Fundamentals of Science Research Program, Ossining High School, Ossining, NY, 10562, USA.
authors: Kiran
authors: K
authors: Groveas
authors: Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
authors: Calum
authors: C
authors: Campbell
authors: Department of Biology, University of Massachusetts, Amherst, MA, 01003, USA.
authors: R Craig
authors: RC
authors: Albertson
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D023681:Cichlids / Q000235:genetics*; D004777:Environment; D005247:Feeding Behavior; D005828:Genetics, Population; D006824:Hybridization, Genetic; D010641:Phenotype; D040641:Quantitative Trait Loci
keywords: cichlid; craniofacial; cryptic genetic variation; phenotypic plasticity; quantitative trait loci