Gene

Engineering

Philosophy

Aerospace engineering

Biology

Wing

Selection (genetic algorithm)

Computer science

Evolutionary biology

Genetics

Anatomy

Phylogenetics

Artificial intelligence

Evolutionary developmental biology

Novelty

Convergent evolution

Theology

Dorsum

Natural selection

Nature Ecology & Evolution

Understanding the origin of novelty is a key question in evolutionary developmental biology. In arthropods, the body wall has served as a repeated source of morphological novelty. In treehoppers, an ancestrally flat part of the dorsal body wall (the pronotum) was transformed into a three-dimensional structure (the helmet), which was subsequently moulded by natural selection into diverse shapes. Here, we test three hypotheses for the developmental origin of the helmet by comparing body-region transcriptomes in a treehopper and a leafhopper that retains more ancestral morphology. In leafhoppers, pronotal gene expression is most similar to that of its serial homologue, the mesonotum. By contrast, in treehoppers, helmet gene expression is most similar to that of wings, supporting the wing-patterning network co-option hypothesis for the origin of the helmet. These results suggest that serial homologues may diverge evolutionarily through replacement of, rather than tinkering with, their ancestrally shared patterning network. The treehopper helmet represents a morphologic novelty. Comparison of body-region transcriptomes in a treehopper and a leafhopper supports co-option of the wing-patterning network for the origin of the helmet.

Co-option of wing-patterning genes underlies the evolution of the treehopper helmet