Number of genes controlling a quantitative trait in a hybrid zone of the aposematic frog Ranitomeya imitator.
The number of genes controlling mimetic traits has been a topic of much research and discussion. In this paper, we examine a mimetic, dendrobatid frog Ranitomeya imitator, which harbours extensive phenotypic variation with multiple mimetic morphs, not unlike the celebrated Heliconius system. However, the genetic basis for this polymorphism is unknown, and not easy to determine using standard experimental approaches, for this hard-to-breed species. To circumvent this problem, we first develop a new protocol for automatic quantification of complex colour pattern phenotypes from images. Using this method, which has the potential to be applied in many other systems, we define a phenotype associated with differences in colour pattern between different mimetic morphs. We then proceed to develop a maximum-likelihood method for estimating the number of genes affecting a quantitative trait segregating in a hybrid zone. This method takes advantage of estimates of admixture proportions obtained using genetic data, such as microsatellite markers, and is applicable to any other system where a phenotype has been quantified in an admixture/introgression zone. We evaluate the method using extensive simulations and apply it to the R. imitator system. We show that probably one or two, or at most three genes, control the mimetic phenotype segregating in a R. imitator hybrid zone identified using image analyses.
Department of Applied Mathematics and Computer Science, Technical University of Denmark, Building 324/130, Matematiktorvet, 2800 Kgs Lyngby, Denmark jsve@dtu.dk.
Jacob S
http://orcid.org/0000-0001-6299-3843
JS
Vestergaard
Department of Biology, East Carolina University, Howell Science Complex N314, Greenville, NC 27858, USA.
Evan
E
Twomey
Department of Applied Mathematics and Computer Science, Technical University of Denmark, Building 324/130, Matematiktorvet, 2800 Kgs Lyngby, Denmark.
Rasmus
R
Larsen
Department of Biology, East Carolina University, Howell Science Complex N314, Greenville, NC 27858, USA.
Kyle
K
Summers
Department of Integrative Biology, University of California Berkeley, 4098 VLSB, Berkeley, CA 94720, USA.
Rasmus
R
Nielsen
D000818:Animals; D001001:Anura / Q000235:genetics*; D051456:Gene Flow; D014644:Genetic Variation; D016013:Likelihood Functions; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics; D019655:Quantitative Trait, Heritable
Ranitomeya imitator; hybridization; image analysis; quantitative phenotyping