Evolution, religion, and ignorance.

[Angrboda]

I'm not even sure what "existing variation potential" means. It seems like another offshoot of whatever mechanism you think exists that prevents the crossing of species lines, to me. Any variation is evolution, and I'd like to know how you demonstrate and quantify that this is due to some nebulous "potential."

I should have said genetic diversity.
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.

Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment. Those individuals are more likely to survive to produce offspring bearing that allele. The population will continue for more generations because of the success of these individuals.

The lizards adapted to a new environment. We don't know if these adaptations were due to new mutations, as you propose, or from existing genetic diversity. Considering the number of changes and the speed of change, genetic diversity seems like a more likely explanation.

This seems to result in a Hobbesian choice for the macroevolution advocate. If the species divergence is rapid, within an observable time frame, there's reason to suspect the change occurred as a result of pre-existing genetic diversity. If the change occurs outside of an observable time frame, the definitions of species which depend on reproductive compatibility often cannot be applied, and arguments from morphology and taxonomy have to suffice, and those definitions of species cannot establish macroevolution at the genetic level. And a criticism at this level can be aimed at ring species, as a species can contain enough genetic diversity for descendants of two linneages to develop post-zygotic reproductive incompatibility while retaining gene level reproductive compatibility. That two populations in a ring species don't interbreed is not sufficient to demonstrate the type of genetic level reproductive incompatibility that macroevolution requires. It's not even clear whether genetic incompatibility between arms of a ring species demonstrates the kind of genetic change required for macroevolution as commonly proposed. I don't buy the creationist explanations derived from reproductive isolation being a result of the fall, but naturalistic explanations may exist. (The Grey Tree Frog example is a possible counter-example, but again, nobody saw that speciation event either.)