Phosphorus limitation does not drive loss of bony lateral plates in freshwater stickleback (Gasterosteus aculeatus).
Connecting the selective forces that drive the evolution of phenotypes to their underlying genotypes is key to understanding adaptation, but such connections are rarely tested experimentally. Threespine stickleback (Gasterosteus aculeatus) are a powerful model for such tests because genotypes that underlie putatively adaptive traits have been identified. For example, a regulatory mutation in the Ectodysplasin (Eda) gene causes a reduction in the number of bony armor plates, which occurs rapidly and repeatedly when marine sticklebacks invade freshwater. However, the source of selection on plate loss in freshwater is unknown. Here, we tested whether dietary reduction of phosphorus can account for selection on plate loss due to a growth advantage of low-plated fish in freshwater. We crossed marine fish heterozygous for the 16 kilobase freshwater Eda haplotype and compared the growth of offspring with different genotypes under contrasting levels of dietary phosphorus in both saltwater and freshwater. Eda genotype was not associated with growth differences in any treatment, or with mechanisms that could mitigate the impacts of phosphorus limitation, such as differential phosphorus deposition, phosphorus excretion, or intestine length. This study highlights the importance of experimentally testing the putative selective forces acting on phenotypes and their underlying genotypes in the wild.
['Archambeault|Sophie L|SL|0000-0001-9409-7541', 'Durston|Daniel J|DJ|', 'Wan|Alex|A|', 'El-Sabaawi|Rana W|RW|', 'Matthews|Blake|B|', 'Peichel|Catherine L|CL|0000-0002-7731-8944']
D000483:Alleles D000818:Animals D001846:Bone Development D001842:Bone and Bones D004032:Diet D005260:Female D005618:Fresh Water D006579:Heterozygote D006720:Homozygote D007422:Intestines D008136:Longevity D008297:Male D010758:Phosphorus D054712:Salinity D012623:Seawater D023701:Smegmamorpha
phosphorus threespine stickleback Ectodysplasin (Eda) Ecological stoichiometry growth trade-off hypothesis salinity