Came across this paper that came out yesterday:
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Great abstract. Glad someone is explicitly stating the role of interspecific competition.
I also agree that it is a great abstract. As many of us have been saying for a while, macroevolution is essentially microevolution combined with speciation. The author also does a great job of explaining the impact of intra- and interspecies competition.
The one remaining problem is how to define macroevolution in terms of phyletic gradualism (i.e. anagenesis).
I don’t think that’s the lesson of the abstract, and presumably of the paper. The author favors definition 3, which doesn’t involve microevolution. I think you’re implicitly assuming definition 1 or 2. And by definition 3, macroevolution has nothing to do with anagenesis.
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Abstract
“Definitions of macroevolution fall into three categories: (1) evolution of taxa of supraspecific rank; (2) evolution on the grand time‐scale; and (3) evolution that is guided by sorting of interspecific variation (as opposed to sorting of intraspecific variation in microevolution). Here, it is argued that only definition 3 allows for a consistent separation of macroevolution and microevolution. Using this definition, speciation has both microevolutionary and macroevolutionary aspects: the process of morphological transformation is microevolutionary, but the variation among species that it produces is macroevolutionary, as is the rate at which speciation occurs. Selective agents may have differential effects on intraspecific and interspecific variation, with three possible situations: effect at one level only, effect at both levels with the same polarity but potentially different intensity, and effects that oppose between levels. Whereas the impact of all selective agents is direct in macroevolution, microevolution requires intraspecific competition as a mediator between selective agents and evolutionary responses. This mediating role of intraspecific competition occurs in the presence of sexual reproduction and has therefore no analogue at the macroevolutionary level where species are the evolutionary units. Competition between species manifests both on the microevolutionary and macroevolutionary level, but with different effects. In microevolution, interspecific competition spurs evolutionary divergence, whereas it is a potential driver of extinction at the macroevolutionary level. Recasting the Red Queen hypothesis in a macroevolutionary framework suggests that the effects of interspecific competition result in a positive correlation between origination and extinction rates, confirming empirical observations herein referred to as Stanley’s rule.”
This sentence would be difficult to explain to a YEC yearning to understand Evolution - -
“…Speciation has both microevolutionary and macroevolutionary aspects: the process of morphological transformation is microevolutionary, but the variation among species that it produces is macroevolutionary, as is the rate at which speciation occurs.”
The usual irony is left vaguely treated: much of the change that occurs to a population that differentiates into 2 or more species is technically micro-evolution in the sense that it is only the last bit of change that creates the reproductive differences that make two or more sub-populations genetically distinct. Up until that reproductive compatibility is definitively curtailed, the changes are “micro” - - breeding within the sub-populations is still technically possible.
Ernst Mayr would have noted that it is only the last bit of “micro” change that seals off one species from another. This is very difficult to explain to the typical YEC.
Once speciation occurs, and especially under environmental stresses, speciated sub-populations can begin to dramatically differentiate in appearance from the original population of common ancestors!