Characterization of papilionid aberrations and their implications for the groundplan model

The immense diversity of butterfly wing color patterns has led to the construction of ground plans, which is a hypothetical wing pattern archetype thought to be modified through evolution to produce new patterns. Importantly, ground plan models can be used to relate the homology relationships of pattern elements between major lineages. However, to date, there is only one well substantiated ground plan, based on the Nymphalidae (Nijhout 1991). The goal of this study was to revisit the Papilionidae ground plan (Schwanwistch 1943) by interpreting ground plan pattern changes in cases of natural papilionid aberrations (extreme phenotypic variation) and laboratory-induced mutations/perturbations. Laboratory phenotypes for several Papilio species were induced by using pharmaceutical injections and CRISPR to manipulate Wnt family signaling ligands, previously shown to have a central role in the development of ground plan patterns in Nymphalidae (Mazo-Vargas et al. 2017). Ultimately, an attempt was made to characterize the natural aberrations in relation to the laboratory phenotypes and identify major trends. It was found that pattern elements affected by Wnt manipulation were also those that were commonly subject to aberrations in natural specimens. Moreover, natural and laboratory phenotypes were not contradictory in the directionalities (expansion or reduction) of elements that were affected in concert. These results implicate Wnt as a principal modulator of the natural wing pattern variation observed in Papilio and provide valuable insight on the behavior of several papilionid ground plan elements including glauca, umbra, and the submarginal spots.