Morphology should not be forgotten in the era of genomics—a phylogenetic perspective

Abstract

Morphology has traditionally played a pivotal role in animal phylogeny since the first evolutionary biologists began to decipher the animal tree of life. In recent times, however, morphological characters have lost prominence in inferring deep relationships among animals due to fundamental issues with homology statements and the choice of higher taxa as terminals, but most importantly, due to declining costs of generating molecular data. As genomes and transcriptomes become widely available, the burden of evidence for morphology in overcoming molecular tree topologies has become ever heavier. In addition, collection and coding of morphological characters must accelerate and become less subjective. These needs have led to developments in the field of ontology, the use of a controlled and formalized morphological vocabulary. Finally, the role of fossils for dating molecular phylogenies is discussed. While molecules seem to have displaced morphology for phylogenetic inference, the need to incorporate fossils as explicit terminals, including dating of molecular-driven trees, together with new methods for high-throughput morphological data acquisition and annotation, may rescue morphology to become again an important player in phylogenetics. The reasons for maintaining a research program in morphology are thus countless, as ultimately, a zoologist’s interest is to understand form and function, ecology and evolution, as well as all other aspects that may explain how our favorite organisms live, behave and evolve.