Will there ever be a tree of life that systematists can agree on?

Abstract

Since the concept of a “Tree of Life” was raised by Charles Darwin, researches in this field have not only contributed to our understanding of phylogenetic relationships among taxa, but also significantly accelerated the development of related subjects in biological science. Evolutionary biologist Dobzhansky once remarked that “nothing makes sense in biology except in the light of evolution”, which has been largely echoed by later biologists. Indeed, reconstruction of an accurate phylogeny of the living world is very important for biological classification and nomenclature, and also crucial to elucidate the origin and diversification of life. We have experienced three major phases for Tree of Life reconstruction in the past century. Prior to the 1990s, taxonomists published classification systems that were largely dependent on morphological characters. DNA sequencing technology facilitated by the development of polymerase chain reaction (PCR) techniques has allowed systematists to reconstruct phylogenetic relationships using molecular data. More recently, the rapid development of next-generation sequencing tools has brought the Tree of Life to a phylogenomic era by enabling the construction of phylogenies using hundreds or thousands of loci from organellar and nuclear genomes. However, significant conflicts have been detected in phylogenies of various organisms with the large increase in the number of loci used for phylogenetic analyses. Given the level of conflict in some data sets, some researchers have begun to doubt the accuracy and congruence of the Tree of Life and its applications in related biological fields. So, will there ever be a Tree of Life that systematists can agree on?