Assignment Given the Network Model Reconsider the Nature of Evolutionary Processes

If the network model (e.g., Fig. 15.1b) proves to be more nearly correct for many taxonomic groups, then the challenges for systematics and evolutionary biology will be entirely different (McCarthy, 2008). First, phylogeneticists would have to admit that their dream of reconstructing a branched tree of life had been merely a pipedream, and they would have to accept the new and probably far more difficult challenge of working out the precise history of reticulation events for each organismal group and how such reticulate genealogical histories have idiosyncratically distributed particular bits and pieces of DNA from disparate sources to extant taxa. Traditional concepts of species, phylogeny, ancestry, and classification, as well as the significance of reproductive isolation, would all have to be reevaluated. Biologists would have to embrace the notion that biological processes falling somewhat outside the standard neo-Darwinian paradigm for speciation (such as interspecific hybridization and the reproductive stabilization of genetic-recombinant derivatives) could play major and previously underappreciated roles in evolution. They would have to reevaluate the origins of genetic variation on which natural selection acts and how novel phenotypic adaptations and different forms of life mechanistically come into being. In short, major shifts in evolutionary thought would be required, and this would open wonderful opportunities for the eventual emergence of a grandly updated evolutionary synthesis, 21st-century style.

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