Recent reading: 2 Sept 2022

A grand old coast live oak for a new semester (jby)

It’s the end of the first week of classes on my campus, after a spring and summer of more or less successful, mostly in-person conferences (more on that later, I think). I’ve got two big lecture sections of Evolutionary Biology students who are actually in the room with me (still mostly masked, per common sense and campus policy) and the adjustment to non-videoconferenced class has been really delightfully easy. Breakout discussions don’t take an extra five minutes of everyone negotiating an online interface; I can actually hear when someone (it’s usually just one) catches and reacts to one of my passing jokes. There’s energy.

It was also, mostly, a pretty productive and enjoyable summer. There were the conferences; and I got to see some of a state and a biome I’d never visited before. I saw a graduate student through her thesis defense, shepherded one big paper to final acceptance and advanced some others, finalized the hiring of the lab’s first postdoc, and got word I’d earned tenure, a year early. I think I’m going to be spending a lot of the coming semester figuring out what my research program looks like now that it’s as “established” as it can be, and that’s exciting in a way I haven’t felt since I started as faculty.

And here’s some of what I’ve been reading, as I’m thinking about this new phase:

Cohen ZP, YH Chen, R Groves, and SD Schoville. 2022. Evidence of hard-selective sweeps suggest independent adaptation to insecticides in Colorado potato beetle (Coleoptera: Chrysomelidae) populations. bioRxiv doi: 10.1101/2022.08.15.504016

  • Whole-genome resequencing for two pesticide-resistent beetle populations, in Long Island, NY and Wisconsin
  • Reconstructs recombination and population demography; Wisconsin has smaller NE (though CIs widely overlap) — serial founder events?
  • Identify sweep targets by comparison to demographic simulation, which include genes in detoxification pathways

Bergman J et al. 2022. Worldwide late-Quaternary population declines in extant megafauna are due to Homo sapiens rather than climate. bioRxiv doi: 10.1101/2022.08.13.503826

The authors infer the timing of demographic declines in 142 megafauna species using whole-genome sequence data pinpointing 100kya as a critical transition point. They find that human settlement times are a better predictor of reconstructed megafaunal decline timing than climate. The reconstructions of effective population size allow a back-of-the-envelope estimate of census population and biomass declines as well, and this suggests losses of something like 75% from a “baseline” before 100kya. “These observations imply that the worldwide expansion of H. sapiens caused a major restructuring of ecosystems at global scale,” the abstract concludes, dryly.

Irwin D and D Schluter. 2022. Hybridization and the coexistence of species. American Naturalist doi: 10.1086/720365

  • Models the coexistence of two diverged populations/species in a contact zone, taking into account both their ecological differentiation (i.e., reduced competition for resources) and selection against hybrids (reproductive isolation) to try to unify ecological and evolutionary theory of species coexistence.
  • “… even a small rate of interbreeding can dramatically alter the conditions under which two differentiated populations can persist in sympatry.” — If assortative mating is even somewhat possible, even with complete specialization on different resources, the two species merge into a single hybrid swarm.
  • Ecological differentiation is, however, necessary for stable coexistence of two species.
  • First paper I’ve ever seen that cites an earlier version posted to bioRxiv (to demonstrate that porting the model from R to Julia didn’t change results)

About Jeremy Yoder

Jeremy B. Yoder is an Assistant Professor of Biology at California State University Northridge, studying the evolution and coevolution of interacting species, especially mutualists. He is a collaborator with the Joshua Tree Genome Project and the Queer in STEM study of LGBTQ experiences in scientific careers. He has written for the website of Scientific American, the LA Review of Books, the Chronicle of Higher Education, The Awl, and Slate.
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