Inferring processes of coevolutionary diversification in a community of Panamanian strangler figs and associated pollinating wasps*

Abstract

The fig and pollinator wasp obligate mutualism is diverse (∼750 described species), ecologically important, and ancient (∼80 Ma). Once thought to be an example of strict one‐to‐one cospeciation, current thinking suggests genera of pollinator wasps codiversify with corresponding sections of figs, but the degree to which cospeciation or other processes contribute to the association at finer scales is unclear. Here, we use genome‐wide sequence data from a community of Panamanian strangler figs and associated wasp pollinators to estimate the relative contributions of four evolutionary processes generating cophylogenetic patterns in this mutualism: cospeciation, host switching, pollinator speciation, and pollinator extinction. Using a model‐based approach adapted from the study of gene family evolution, our results demonstrate the importance of host switching of pollinator wasps at this fine phylogenetic and regional scale. Although we estimate a modest amount of cospeciation, simulations reveal the number of putative cospeciation events to be consistent with what would be expected by chance. Additionally, model selection tests identify host switching as a critical parameter for explaining cophylogenetic patterns in this system. Our study demonstrates a promising approach through which the history of evolutionary association between interacting lineages can be rigorously modeled and tested in a probabilistic phylogenetic framework.

Sequence capture phylogenomics of historical ethanol‐preserved museum specimens: Unlocking the rest of the vault

“…Other extraction techniques tested on small‐bodied low‐input samples, for example using Chelex (Lienhard & Schäffer, ), may yield more DNA than the method used here, but this comparison remains to be tested. In extremely small‐bodied specimens with low input DNA, whole genome amplification following DNA extraction has been successfully used to increase DNA yield for library preparation (Branstetter, Ješovnik, et al, ; Satler et al, ). It would be beneficial to test multiple whole genome amplification protocols specifically targeting small‐bodied and highly degraded museum specimens.…”

Digest: Process‐based phylogenetic models provide unique insights into the evolution of mutualistic networks*

“…The DTL method, for example, cannot accommodate species with multiple hosts, which the authors acknowledge and deal with in a creative and sensible way. In this study, Satler et al (2019) had the good fortune that only a few of the fig wasps in their study system interacted with multiple fig tree species. However, in more complex mutualistic systems, the interaction problem could become much more pronounced as it is likely that multiple pollinator species will interact with multiple host species.…”

“…We hope that the exciting work of Satler et al. () inspires other researchers studying ecological networks to think more probabilistically and to start developing entirely new classes of coevolutionary models.…”

“…Ideally, it would be possible to model reciprocal feedbacks of coevolved traits and to simultaneously estimate evolutionary parameters for both groups of interacting species (Harmon et al 2019). We hope that the exciting work of Satler et al (2019) inspires other researchers studying ecological networks to think more probabilistically and to start developing entirely new classes of coevolutionary models.…”

“…In this issue, Satler et al. () take a novel approach to investigating the processes involved in generating the observed cophylogenetic patterns in the fig–fig wasp mutualism. They borrow an approach from molecular evolution that was originally developed to explain why a gene family phylogeny differs from a species phylogeny.…”