title: Complex constraints on allometry revealed by artificial selection on the wing of Drosophila melanogaster.
abstract: Precise exponential scaling with size is a fundamental aspect of phenotypic variation. These allometric power laws are often invariant across taxa and have long been hypothesized to reflect developmental constraints. Here we test this hypothesis by investigating the evolutionary potential of an allometric scaling relationship in drosophilid wing shape that is nearly invariant across 111 species separated by at least 50 million years of evolution. In only 26 generations of artificial selection in a population of Drosophila melanogaster, we were able to drive the allometric slope to the outer range of those found among the 111 sampled species. This response was rapidly lost when selection was suspended. Only a small proportion of this reversal could be explained by breakup of linkage disequilibrium, and direct selection on wing shape is also unlikely to explain the reversal, because the more divergent wing shapes produced by selection on the allometric intercept did not revert. We hypothesize that the reversal was instead caused by internal selection arising from pleiotropic links to unknown traits. Our results also suggest that the observed selection response in the allometric slope was due to a component expressed late in larval development and that variation in earlier development did not respond to selection. Together, these results are consistent with a role for pleiotropic constraints in explaining the remarkable evolutionary stability of allometric scaling.
authors.affiliation: Norwegian Institute for Nature Research, 7485 Trondheim, Norway; Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway; Department of Biological Science, Florida State University, Tallahassee, FL 32306; geir.bolstad@nina.no.
authors.forename: Geir H
authors.initials: GH
authors.lastname: Bolstad
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306;
authors.forename: Jason A
authors.initials: JA
authors.lastname: Cassara
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306;
authors.forename: Eladio
authors.initials: E
authors.lastname: Márquez
authors.affiliation: Department of Biology, CEES & EVOGENE, University of Oslo, 0316 Oslo, Norway.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Hansen
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306;
authors.forename: Kim
authors.initials: K
authors.lastname: van der Linde
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306;
authors.forename: David
authors.initials: D
authors.lastname: Houle
authors.affiliation: Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway;
authors.forename: Christophe
authors.initials: C
authors.lastname: Pélabon
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D004331:Drosophila melanogaster / Q000033:anatomy & histology* / Q000235:genetics; D008957:Models, Genetic; D010641:Phenotype; D012641:Selection, Genetic; D000068618:Selective Breeding; D014921:Wings, Animal / Q000033:anatomy & histology* / Q000254:growth & development
keywords: allometry; artificial selection; comparative analyses; developmental constraints; pleiotropy