Calibrated phylogeny of Dryophthorinae, showing their Mesozoic diversification following a long temporal lag.
Back in 2011, when I was starting my PhD, I worked for a year on a project that involved getting the first comprehensive molecular phylogeny of Dryophthorinae. These are easily recognizable weevils, not that diverse for weevil standards (about 1,000 species), hugely important for economy and then a model for the study of insect endosymbionts.
However, in 2011 it was not straightforward to obtain molecular data from pinned museum specimens and my attempts at collecting them in the tropics were not very successful, leading to abandonment of the project. I was not the first one: the phylogeny of Dryophthorinae has seemed like low hanging fruit for a while but no one who started it managed to finish. Until now, 10 years later.
Lourdes Chamorro (USDA, Smithsonian Institution) has been focusing on dryophthorids for the last few years, having published an outstanding key based on larval morphology, accomplished important collections of molecular-grade material resulting in new discoveries (such as this and this), and produced morphological and molecular datasets that will still result in more discoveries for the next few years. We joined forces to work on this first comprehensive molecular phylogeny for the group, including a calibrated tree combining ribosomal RNA data with the relatively rich fossil record for the group. It showed us that we still have a lot of work to do on resolving the early branches of the group, but also revealed something surprising. There is a huge temporal lag between the split from platypodines, their closest relatives, and the diversification of extant lineages. All fossils attributable to Dryophthorinae are found in the Cenozoic, while the two groups split in the Jurassic. While platypodines have diversified steadily throughout this time, it seems dryophthorinae explosively diversified in the Cenozoic after the Cretacious-Tertiary boundary. This pattern is remarkably similar to the group of plants that they feed on. Since they are a lot more dependent of specific plants than they fungus-farming sister group, we believe they tracked more closely the rise of angiosperms.
The paper is available here:
Chamorro, ML, de Medeiros, B, Farrell, BD. First phylogenetic analysis of Dryophthorinae (Coleoptera, Curculionidae) based on structural alignment of ribosomal DNA reveals Cenozoic diversification. Ecol Evol. 2021; 00: 1– 15. https://doi.org/10.1002/ece3.7131