Phylogenetics: Heed the father of cladisticsFROM: Nature 496, 295–296
IN On the Origin of Species, Charles Darwin proclaimed that “our classifications will come to be, as far as they can be so made, genealogies”. That turned out to be easier said than done. Even as late as the 1970s, biologists were still grouping animals and plants largely on the basis of overall physical similarity and whether they possessed or lacked certain traits, such as a backbone or the ability to produce flowers.
The German entomologist and palaeontologist Willi Hennig transformed the classification of organisms into the rigorous science of cladistics1, 2, 3, 4, 5. His book Phylogenetic Systematics6, published in 1966, laid out how to construct phylogenetic trees and how to use their branching patterns as the basis for classifications.
Paired with DNA sequencing, Hennig's theories revolutionized our understanding of the relationships among the nearly two million species known today. In the history of biological classification, the little-known Hennig arguably deserves a place alongside Aristotle, Carl Linnaeus and Darwin.
But two key messages from his book have been lost in the nearly half-century since it was published: the importance of detailed studies of the development and evolution of complex characters, such as the horn of a rhinoceros or the pincer of a fiddler crab; and the use of all relevant evidence — molecular, anatomical, fossil and developmental — in mapping evolutionary relationships. Too often these days, DNA information is favoured over everything else, and when conflicts arise between DNA-based analyses and those reliant on morphology, the former is frequently assumed to be correct, even though many uncertainties surround the molecular basis of evolution.GERD HENNIGWilli Hennig in 1960.
Hennig was born 100 years ago this week, on 20 April 1913. In celebration of his impact on phylogenetics and classification, we urge biologists to heed his call to embrace all the relevant data.
LEER MAS >