title: Cryptic individual scaling relationships and the evolution of morphological scaling.
abstract: Morphological scaling relationships between organ and body size-also known as allometries-describe the shape of a species, and the evolution of such scaling relationships is central to the generation of morphological diversity. Despite extensive modeling and empirical tests, however, the modes of selection that generate changes in scaling remain largely unknown. Here, we mathematically model the evolution of the group-level scaling as an emergent property of individual-level variation in the developmental mechanisms that regulate trait and body size. We show that these mechanisms generate a "cryptic individual scaling relationship" unique to each genotype in a population, which determines body and trait size expressed by each individual, depending on developmental nutrition. We find that populations may have identical population-level allometries but very different underlying patterns of cryptic individual scaling relationships. Consequently, two populations with apparently the same morphological scaling relationship may respond very differently to the same form of selection. By focusing on the developmental mechanisms that regulate trait size and the patterns of cryptic individual scaling relationships they produce, our approach reveals the forms of selection that should be most effective in altering morphological scaling, and directs researcher attention on the actual, hitherto overlooked, targets of selection.
authors.affiliation: Department of Integrative Biology, Michigan State University, East Lansing, Michigan, 48824.
authors.forename: Austin P
authors.initials: AP
authors.lastname: Dreyer
authors.affiliation: Department of Biology, Lake Forest College, Lake Forest, Illinois, 60045.
authors.forename: Omid
authors.initials: O
authors.lastname: Saleh Ziabari
authors.affiliation: College of Biological Sciences, University of Minnesota, St Paul, Minnesota, 55108.
authors.forename: Eli M
authors.initials: EM
authors.lastname: Swanson
authors.affiliation: Department of Statistics and Probability, Michigan State University, East Lansing, Michigan, 48824.
authors.forename: Akshita
authors.initials: A
authors.lastname: Chawla
authors.affiliation: Department of Biology and Biochemistry, University of Houston, Houston, Texas, 77204.
authors.forename: W Anthony
authors.initials: WA
authors.lastname: Frankino
authors.affiliation: Department of Biology, Lake Forest College, Lake Forest, Illinois, 60045. shingleton@lakeforest.edu.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Shingleton
mesh_terms: D000818:Animals; D049628:Body Size / Q000235:genetics*; D008957:Models, Genetic; D010641:Phenotype; D012641:Selection, Genetic
keywords: Allometry; body proportion; body size; mathematical modelling; morphological scaling; nutrition; shape