Transposable elements vs mutation-driven evolution
October 9, 2013 | James Kohl
Mutation-driven evolution, page 196: “…natural selection is an evolutionary process initiated by mutation.”
In my October 7, 2013 blog post “The peppered moth example (revisited)” I wrote: “There is probably no better example of ignorance in the context of biologically based cause and effect, than the peppered moth.”
On October 9, 2013, we read Evolution in Color: From Peppered Moths to Walking Sticks by Carl Zimmer, who tells us: “… the evidence in favor of natural selection on peppered moths continued to accumulate. For one thing, Britain and other countries cleaned up their air in the late 1900s, and trees went from dark to light. Now natural selection’s balance shifted: black became a liability. And, as you’d predict, the dark moths went from common back to rare again.”
My comment: As indicated in my quote (above) from the book Mutation-driven evolution, the peppered moth was a model of how mutations supposedly led to the color change that enabled natural selection via predation. See for example this comment “A greater understanding of the peppered moth’s genetics will “complete the package” of research on “the best example of adaptation involving natural selection that we have”, says Bruce Grant, a retired population geneticist…” That comment was echoed in the context of mutations theory here: “Robert Reed, an evolutionary developmental biologist at the University of California… said: ‘The fact that the carbonaria mutation maps to the same region as butterfly wing pattern genes is amazing.
What is “amazing” about the “best example of adaptation involving mutation-initiated natural selection that we have” is that no one attempted to explain how the mutation that initiated the natural selection came and went. It arrived with the pollution and somehow effected what was claimed to be a population-wide color change in a moth species. But the moth species changed color again when the pollution was controlled. The mutation-initiated natural selection that comes and goes defies explanation via any current perspective on mutation-driven evolution, unless a a second mutation caused the change back to the original color.
The changes can, however, be explained without any theory about the involvement of mutations that come and go in moths or any other species. We now know that transposable elements (TEs) profoundly alter genome structure, function and evolution. We can use what’s known to explain the changes in the peppered moths and in other insect.
Background: Lepidoptera is a large order of insects that includes moths and butterflies. Bombyx mori is the moth species that was the first lepidopteran to have its genome sequenced. Heliconius melpomene is a lepidopteran butterfly species. The H. melpomene genome is the third lepidopteran genome to be sequenced. The TE landscape of H. melpomene is distinct compared to B. mori (see for review: Lavoie et al, 2013).
Explaining adaptive evolution sans mutations. In B. mori, differences in the TE landscape compared to H. melpomene correlate with differences between the behavior of males and females that are pheromone-dependent. That fact literally helped to define the term “pheromones” in 1959. Others may now be aware of experimental evidence that shows species-specific mutations are not likely to be fixed in the DNA of the organized genome of any species. That biological fact means mutations cannot contribute anything whatsoever to natural selection. Given current knowledge of biological facts that can be compared to evolutionary theories, which have never been supported by experimental evidence, the role of TEs in pheromone-controlled adaptive evolution via sexual selection for pheromones may become clearer.
Explaining nutrient-dependent pheromone-controlled adaptive evolution via TEs. Most people intuitively grasp one of the basic principles of biology, which is that nutrients are required to support life. Naturally, that means nutrients must be selected in all species. The metabolism of nutrients to species-specific pheromones controls reproduction. The levels of biological organization, which are required to link sensory cause to behavioral affect in species from microbes to man, incorporate the role of TEs in the nutrient-dependent pheromone-controlled reproduction of lepidoptera. Indeed, the TEs probably come from what organism eat and are transposed based on feedback loops that allow pheromones to control the amount of transposed elements by controlling reproduction.