Complex, nongradual responses to environmental conditions are commonplace in nature and perhaps most extreme in polyphenic insects where continuous variation in nutrition experienced in early development gives rise to discrete alternative castes or morphs. This research shows that the hedgehog (Hh) pathway has acquired a novel and highly unusual role in the nutrition-dependent regulation of polyphenic development of a beetle. Experimental repression of Hh signaling returns a highly discontinuous response to nutrition to its presumed ancestral, gradual state. Our results suggest that recruitment of the Hh signaling pathway may have been a key step in the evolution of trait thresholds and the corresponding origin of alternative phenotypes and complex allometries.
“If you put these two pathways together,” Moczek said, “the result is the first comprehensive developmental genetic explanation of a nutrition-dependent developmental threshold, a phenomenon that biologists have been trying to explain for a very long time.”
My comment: We put the two pathways together in the molecular epigenetics section of our 1996 Hormones and Behavior review. We did not specifically state that ecological variation in the supply of food was the link from molecular epigenetics to all RNA-mediated cell type differentiation, which we showed was controlled by the physiology of reproduction. Somethings need not be said to an audience of biologically informed peers.
The fact that all morphological and behavioral species traits are nutrition-based is something that these authors must want their biologically uninformed audience to know.
See for comparison: Nutrient-dependent/pheromone-controlled adaptive evolution: a model
My comment: Why doesn’t everyone already know that nutrition-dependent developmental thresholds are controlled by the physiology of reproduction in all living genera? Why are Kijimoto and Moczek simply restating the well-known fact as if they had discovered it? Is the discovery of the pathway more important than acknowledging the fact that we linked everything known about molecular epigenetics to the pathway ~20 year ago. The pathway does not vary in species from microbes to humans. That is the point Kijimoto and Moczek (2016) are trying to make clear.
By not making any claims about mutations and natural selection they also make it clear why we did not make any claims about mutations and natural selection in our 1996 review. All claims about mutations and natural selection require a belief in magic that has now been compared to facts about energy-dependent RNA-mediated cell type differentiation. Virus-driven energy theft causes the mutations, which are linked to all pathology. It is not possible to link mutations to the creation of one species from another via natural selection. Olfaction; the innate immune system; biophysically constrained energy-dependent protein folding chemistry, and RNA-mediated amino acid substitutions link ecological variation to the physiology of reproduction and supercoiled DNA, which protects all organized genomes from virus-driven entropy.
Secreting and Sensing the Same Molecule Allows Cells to Achieve Versatile Social Behaviors 2014
Feedback loops link odor and pheromone signaling with reproduction 2005
Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors 2012
Human pheromones: integrating neuroendocrinology and ethology 2001
See also the discussion of You are what you eat: IU biologists map genetic pathways of nutrition-based species traits on the Creationism FB group.
See also the discussion of Mutation-driven evolution