Food odors and pheromones in flies (but not in flycatchers?)

Uncovering the genomic signatures of species differences in flycatchers. Speciation genetics (2013)  B Hansson.

Bill S. Hansson co-authored Attraction of Drosophila melanogaster males to food-related and fly odours

Abstract excerpt: “We showed that upwind flights are initiated by food odours. At shorter distances, males are attracted by volatiles produced by conspecifics. However, only odours produced by copulating flies attract males. This suggests either a synergistic effect of both male and female odours or changes in pheromone release during mating, that indicate the presence of sexually receptive females. Our findings demonstrate the essential role of food odours and pheromones for mate location in D. melanogaster.”

My comment: Is the same author/co-author suggesting that species differences in flies (D. melanogaster) might arise via different molecular mechanisms in flycatchers? If so, perhaps there is something to be said for mutations theory after all. But, I doubt it!

I’m more inclined to believe that the molecular mechanisms of speciation genetics are the same in species from microbes to man (as in my model).  Apparently, we can still rule out random mutations theory, however. For example, Hansson (2013) states:  “The divergence islands were non-randomly distributed across the genome and highly overrepresented towards chromosome ends.”

That suggests adaptive evolution occurs in flies and in flycatchers via the same non-random molecular mechanisms involving nutrient (e.g., food odors) and social odors (e.g., pheromones). But, until someone like Hansson clarifies how adaptive evolution occurs in some invertebrates but not vertebrates, most people may need to determine for themselves whether speciation is caused by food odors and pheromones (as in flies) or via unknown molecular mechanisms (as in flycatchers).

See also: Divergence of odorant signals within and between the two European subspecies of the house mouse. Behavioral Ecology (2008). “Our earlier studies documented mate preference and signal divergence between the 2 subspecies. Hence, we consider the role of the urinary odors as mating signals. We discuss how signal divergence between the 2 subspecies may relate to reproductive character displacement.”

And see: On the scent of speciation: the chemosensory system and its role in premating isolation.  Heredity (2009). “Although most studies of chemosensory speciation concern sexual isolation mediated by pheromone divergence, especially in Drosophila and moth species, other chemically based behaviours (habitat choice, pollinator attraction) can also play an important role in speciation and are likely to do so in a wide range of invertebrate and vertebrate species.”

My comment: If species divergence is not nutrient-dependent and pheromone-controlled in Drosophilia and moth species and in all invertebrates and in all vertebrates, like mice and flycatchers, what drives and controls species divergence? Is there a model for that?