title: Evolution of the Genotype-to-Phenotype Map and the Cost of Pleiotropy in Mammals.
abstract: Evolutionary studies have long emphasized that the genetic architecture of traits holds important microevolutionary consequences. Yet, studies comparing the genetic architecture of traits across species are rare, and discussions of the evolution of genetic systems are made on theoretical arguments rather than on empirical evidence. Here, we compared the genetic architecture of cranial traits in two different mammalian model organisms: the gray short-tailed opossum, Monodelphis domestica, and the laboratory mouse, Mus musculus We show that both organisms share a highly polygenic genetic architecture for craniofacial traits, with many loci of small effect. However, these two model species differ significantly in the overall degree of pleiotropy, N, of the genotype-to-phenotype map, with opossums presenting a higher average N They also diverge in their degree of genetic modularity, with opossums presenting less modular patterns of genetic association among traits. We argue that such differences highlight the context dependency of gene effects, with developmental systems shaping the variational properties of genetic systems. Finally, we also demonstrate based on the opossum data that current measurements for the relationship between the mutational effect size and N need to be re-evaluated in relation to the importance of the cost of pleiotropy for mammals.
authors: Department of Biology, Washington University in St Louis, Missouri 63130 arthur.porto@utrgv.edu.|South Texas Diabetes and Obesity Institute, The University of Texas Rio Grande Valley, Brownsville, Texas 78520.
authors: Arthur
authors: A
authors: Porto
authors: Department of Biology, Loyola University Chicago, Illinois 60660.
authors: Ryan
authors: R
authors: Schmelter
authors: South Texas Diabetes and Obesity Institute, The University of Texas Rio Grande Valley, Brownsville, Texas 78520.
authors: John L
authors: JL
authors: VandeBerg
authors: Laboratório de Evolução de Mamíferos, Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, 05508-090, Brazil.
authors: Gabriel
authors: G
authors: Marroig
authors: Department of Biology, Loyola University Chicago, Illinois 60660.
authors: James M
authors: JM
authors: Cheverud
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D058685:Genetic Pleiotropy; D005838:Genotype; D051379:Mice; D008957:Models, Genetic; D048309:Monodelphis / Q000235:genetics
keywords: complexity; genetic architecture; marsupials