How the Easter Egg Weevils got their spots: Phylogenomics reveals Müllerian mimicry in Pachyrhynchus (Coleoptera, Curculionidae)

The evolutionary origins of mimicry in the Easter Egg weevil, Pachyrhynchus, have fascinated researchers since first noted more than a century ago by Alfred Russel Wallace. Müllerian mimicry, or mimicry in which two or more distasteful species look similar, is widespread throughout the animal kingdom. Given the varied but discrete color patterns in Pachyrhynchus, this genus presents one of the best opportunities to study the evolution of both perfect and imperfect mimicry. We analyzed more than 10,000 UCE loci using a novel partitioning strategy to resolve the relationships of closely related species in the genus. Our results indicate that many of the mimetic color patterns observed in sympatric species are due to convergent evolution. We suggest that this convergence is driven by positive frequency-dependent selection.Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: 1856402Divergence Dating Biogeography We used MCMCTREE (Yang 2007) to perform our divergence dating analyses. We used the topology from our ASTRAL analyses as the starting topology for the MCMCTREE. No fossils exist for our ingroup or near relatives, so we used a geological calibration for the maximum age of the Philippine Islands. We used 25–30 Ma as the root node of the Pachyrhynchini, an approximate date for the emergence of the Philippine proto-islands proposed by Hall (2002). We used MCMCtreeR (Puttick 2019) to estimate a normal distribution around the maximum age of our calibration point as well as to format the tree file for MCMCTREE. Next, we used the aforementioned tree to obtain a rough estimate of the substitution rate using basml (Dos Reis and Yang 2013). To help accomplish this, we randomly selected 300 loci, using many more will prevent the analysis from completing, as well as using more data is not necessary to approximate the uncertainty of the divergence dates (Dos Reis and Yang 2013; Zhu et al. 2015). Finally, we estimated the gradient and Hessian of the branch lengths (Dos Reis and Yang 2011) to assist in the final estimation of our divergence dates