P2.27 HERITABLE WITHIN-POPULATION VARIATION IN THE NUMBER OF GONADOTROPIN-RELEASING HORMONE NEURONS
A presentation by Katherine E Kaugars et al., from the recent SBN 2012 conference indicates that natural heritable variation in winter reproduction is due to differences in the number of GnRH neurons rather than to differences in activity of GnRH neurons.
This finding is consistent with my model of adaptive evolution via ecological, social, and neurogenic niche construction. In my model, the number of GnRH neurosecretory neurons in the mammalian brain determines subtle variations in GnRH secretion via a diet-responsive hypothalamic neurogenic niche. Transgenerational epigenetic inheritance helps to ensure that the epigenetic effect of nutrient chemicals is similar in similar species. But there are species-specific epigenetic effects of pheromones on the development of the brain and behavior that are responsible for speciation.
On the other hand, I guess random mutations could be responsible for speciation — at least according to some evolutionary theorists who are nevertheless unwilling to answer the question: Is there a model for that?