Phylogenies are primarily of interest for their own sake. Despite biologists’ longstanding interest in generating phylogenies from molecular and other data, additional uses for phylogenetic trees (beyond their mere reconstruction) had not yet been explored extensively.
comparative method; phylogenetic character mapping
Phylogenies are primarily of interest for their own sake. Despite biologists’ longstanding interest in generating phylogenies from molecular and other data, additional uses for phylogenetic trees (beyond their mere reconstruction) had not yet been explored extensively.
By the late 20th century, the field of molecular systematics (see Chapter 31) had grown and matured to the point where phylogenetic trees were routinely being generated for a wide diversity of taxonomic groups. Still, many phylogeneticists viewed their efforts merely as part of a larger effort to catalogue and systematize life’s extraordinary diversity. The stage was set for a new worldview that would integrate molecular phylogenetic findings with the traditional kinds of phenotypic data that had always been the main source of information about organismal relationships. More specifically, molecular phylogenies could be seen to provide the genealogical framework for interpreting the precise evolutionary histories of organismal phenotypic traits. In 1991, a seminal book by Paul Harvey and Mark Pagel crystallized this sentiment into what the authors referred to as “the comparative method”. In that same year, Daniel Brooks and Deborah McLennan expanded the comparative method to the field of ethology (behavior). In 2006, I christened this general method “phylogenetic character mapping”. PCM involves plotting the distributions of alternative phenotypes on molecular phylogenetic trees and thereby deducing ancestral character states at internal nodes and establishing their historical patterns of evolutionary interconversion.
The comparative method has become the de rigueur approach in molecular phylogenetics. Indeed, few researchers would now dispute that merely reconstructing a molecular phylogenetic tree is not the ultimate goal. If the tree is to be of any broader service, surely it must be in terms of understanding exactly how evolutionary conversions took place among particular morphological, physiological, or behavioral character states along nature’s myriad evolutionary pathways.
1. Brooks DR, McLennan DA. Phylogeny, Ecology, and Behavior: A Research Program in Comparative Biology Chicago, IL: University of Chicago Press; 1991.
2. Harvey PH, Pagel MD. The Comparative Method in Evolutionary Biology Oxford, UK: Oxford University Press; 1991.
3. Harvey PH, Leigh Brown AJ, Maynard Smith J, Nee S, eds. New Uses for New Phylogenies. Oxford, UK: Oxford University Press; 1996.
4. Avise JC. Evolutionary Pathways in Nature Cambridge, UK: Cambridge University Press; 2006.