Wanninger A, Martinez P & Meyer NP. 2023.
Front. Ecol. Evol. 11:1307280. doi: 10.3389/fevo.2023.1307280 . Link. Published online 19 October 2023

Introduction

The evolution of animal morphologies has been a preoccupation of biologists at least since the XVIII century, when comparative methods were first used to model the transformations of animal form over evolutionary time. This relevance was encapsulated in Darwin’s dictum: “Morphology [is] the most interesting department of natural history, [which] may be said to be its very soul” (page 434 of On the Origin of Species). Morphology, understood as a hierarchical construct (from molecules to cells, organs, and individuals), is still the central focus of the new field of EvoDevo.

Over the last 15 years, the International Society for Invertebrate Morphology (ISIM) has been meeting regularly to discuss the most current issues in the field. We have witnessed the incorporation of powerful technologies (i.e., single-cell RNA sequencing (scRNA-seq), serial transmission electron microscopy (TEM), and genomics), enabling the study of older problems in a new light. Moreover, the analysis of structures and processes now involves gathering data at different levels of complexity, from transcripts through cell types, tissues, and organs to whole bodies. With the help of phylogenetics and paleontology, the scales of our analyses have both spatial and temporal components. Integrating these data leads us to a more comprehensive study of morphology and easy movement across different scales, a prominent characteristic of presentations at past and present International Congress on Invertebrate Morphology (ICIM) meetings. The last of these, ICIM5, took place in Vienna between the 8th and 12th of August, 2022, and was organized by one of us (Andreas Wanninger). The presentations, ranging from the genomic control of development to cell lineage specification as well as the architecture and function of tissues and organs, showcased a variety of intellectual and methodological approaches that attested to our community’s vibrant activities. Accordingly, ICIM5 embraced a wide field of research areas as is reflected in the meeting’s following core topics: MorphovoDevo; Functional Morphology; Molecular Basis of Morphological Diversity; Morphology in Deep Time; Morphology, Integrative Taxonomy and Phylogeny; Senses, Neurons and Behavior; Technological Advances in Microscopy and Imaging; Evolution of Multicellularity.

Some of these contributions, but also work that has not been presented at ICIM5 including studies on vertebrates, are included in this Research Topic entitled “MorphoEvoDevo: A Multilevel Approach to Elucidate the Evolution of Metazoan Organ Systems.” We thank all colleagues who presented and shared their data and participated in the vital discussions on various topics of animal morphology, function, and evolution during ICIM5, 2022, and to those who contributed to this Research Topic. In the following, we summarize the essence of the papers published herein, grouping them by subject. Papers are bundled together based on the major level of analysis used, thereby being aware that they often tackle similar problems at different scales, an approach that we very much encourage (see also the final discussion for a critical assessment of the state of the field).