Quickly wanted to highlight some of our lab’s publications this year:

1. Out in March, from a side project during my PhD and a collaboration with friend Anne Chambers: Chambers^, EA, RD Tarvin^, JC Santos, SR Ron, M Betancourth-Cundar, DM Hillis, MV Matz, and DC Cannatella. 2023. 2b or not 2b? 2bRAD is an effective alternative to ddRAD for phylogenomics. Ecology and Evolution 13: e9842. PDF • https://doi.org/10.1002/ece3.9842 • Twitter Thread (3/10/23)

2. Out in June, Kate Montana’s undergraduate thesis: Montana, KO, V Ramírez-Castañeda† and RD Tarvin. 2023. Are Pacific Chorus Frogs (Pseudacris regilla) resistant to tetrodotoxin (TTX)? Characterizing potential TTX exposure and resistance in an ecological associate of Pacific Newts (Taricha). Journal of Herpetology 57: 220—228. (Open Access) https://doi.org/10.1670/22-002 • PDF

3. Out in October, Yin Chen Wan’s undergraduate thesis: Wan^, YC, MJ Navarrete^†, LA O’Connell, LH Uricchio, A Roland, ME Maan, SR Ron, M Betancourth-Cundar, MR Pie, K Howell, CL Richards-Zawacki, ME Cummings, DC Cannatella, JC Santos*, and RD Tarvin*. 2023. Selection on visual opsin genes in diurnal Neotropical frogs and loss of the SWS2 opsin in poison frogs. Molecular Biology and Evolution 40: msad206. (Open Access) https://doi.org/10.1093/molbev/msad206 • PDF • Twitter Thread (10/21/22)

4. Out in November, a Tarvin lab collaborative review paper: Tarvin*, RD, KC Pearson*, TE Douglas, V Ramírez-Castañeda, María José Navarrete. 2023. The diverse mechanisms animals use to resist toxins. Annual Review of Ecology, Evolution, and Systematics. https://doi.org/10.1146/annurev-ecolsys-102320-102117 • PDF

5. Also out in November, a response to a commentary about specimen collection: Nachman, MW, … RD Tarvin, et al. 2023. Specimen collection is essential for modern science. PLoS Biology 21:e3002318. https://doi.org/10.1371/journal.pbio.3002318 • PDF

We posted our first two sets of translations from my Breaking Language Barriers Seminar. Check them out here.

• Diaz et al 2006, Biodiversity loss threatens human well-being -- now available in Spanish and Chinese!

• Arguello et al 2019, From genetics to biology: advancing mental health research in the Genomics ERA — abstract now available in Chinese, Spanish, Tamil, and plain language

• Egido et al 2022, Mechanisms and clinical importance of bacteriophage resistance. now available: visual art summarizing concepts in the paper

• Ehrenberg et al. 2021, Launching a saliva-based SARS-CoV-2 surveillance testing program on a university campus. Full article now available in Chinese. Abstracts now available in Chinese, Spanish, Tamil, and plain language.

• Rabe et al. 2020, Post-hurricane shifts in the morphology of island lizards. Abstracts now available in Chinese, Spanish, Tamil, and plain language. Full article available in Spanish (email Becca for access)

• Sidlauskas et al. 2021, Teaching ichthyology online with a virtual specimen collection. Full article now available in Chinese

• Vernier et al. 2020, The gut microbiome defines social group membership in honey bee colonies. Abstracts now available in Chinese, Spanish, Tamil, and plain language.

• Woodmansee et al. 2021, On-ranch adaptation to California’s historic 2012-2016 drought. Abstracts now available in Chinese, Spanish, Tamil, and plain language.

A blog co-authored by Rebecca and several colleagues about language barriers in science has been posted on the multilingual website Global Development Network. It is available in English, French, and Spanish.

And our new perspective piece is out now in BioScience: “Overcoming Language Barriers in Academia: Machine Translation Tools and a Vision for a Multilingual Future”. See the Press Release (English, Español)

See twitter threads in Spanish, Portuguese, and English

Our efforts to establish a proof-of-principle for an ongoing experimental evolution project, led by Tyler Douglas, are now published in Biology Letters! Below, I update our initial Twitter thread on the paper.

Previous studies show that genetic variation exists for nicotine resistance in founding strains of the Drosophila Synthetic Resource Panel (DSPR; Marriage et al. 2014). In our study, we focused on two strains of the DSPR, A4 and A3. A4 has two duplicated cytochrome p450 genes that are constitutively expressed at higher levels than A3. These genes are likely to be in part responsible for breaking down nicotine (Chakraborty et al. 2019). A3 (not A4) has a mutation that disrupts the reading frame of a UGT (an enzyme that can modify nicotine), reducing nicotine resistance (Highfill et al. 2017). The role of this mutation in nicotine resistance was validated using CRISPR (Macdonald & Highfill 2020). Given these data showing that A4 are more resistant than A3 to nicotine, we asked whether A4 could consume enough nicotine to receive a survival benefit against the endoparasitoid wasp Leptopilina heterotoma, which lays its eggs inside fly larvae. Nicotine can potentially permeate the fly gut and enter hemolymph to affect wasp development. The wasps are able to prevent fly larvae from encapsulating the egg (a normal anti-parasite response), so the wasp eggs should be exposed to nicotine in the surrounding hemolymph.

In the first experiment, we parasitized A3 and A4 larvae, placed them on nicotine-laced media, and counted the number of adults emerging alive. Compared to survival on control media, parasitized A4 flies actually had increased survival when fed nicotine (panel a, solid purple line, below). In both fly strains, wasps developing in nicotine-fed flies had much worse survival (panel b).

We then wanted to know whether the flies contained nicotine so we conducted another experiment feeding A3 and A4 flies then collecting and rinsing flies before sending them off to GCMS for nicotine quantification. We estimated that A4 pupae (purple) contained up to 40ng each (panel d) as pupae. We also observed that both fly strains carried nicotine over into adulthood! This is also a pattern that was seen by Karageorgi and colleagues (2019) when "monarch" flies were fed the cardiotoxin ouabain. It’s possible that passive accumulation during larval stages could provide adults a fitness advantage against parasites or predators too. In this experiment, we noted that A4 accrued more nicotine than A3 in the 24hr period after they were first placed on nicotine media (panel d, asterisks). We were surprised by this pattern because given the known metabolic efficiency of A4 we expected the opposite.

In a third experiment, we estimated the adult mass of both strains when fed control or nicotine-laced food. This assay showed that A3 flies (blue) consumed less media than A4 flies (purple), suggesting that A3 flies were limiting their ingestion of nicotine and that A4 flies could survive carrying a heavier nicotine load than A3 flies (panel c). This might be what allowed A4 to accrue a survival benefit against wasps while A3 could not.

To summarize:

1. Upregulation of metabolic enzymes likely allows A4 flies to consume more toxins than A3 flies

2. A4 passively accumulate more toxins than A3

3. A4 flies accrue a nicotine-mediated survival advantage against a parasitoid

4. These patterns don't require active sequestration mechanisms

Together all of these experiments led us to a somewhat surprising conclusion: one of the first steps in the evolution of chemical defense may be natural selection for increased toxin metabolism. Increased toxin intake could result in increased (passive) toxin accumulation, which could in turn provide those individuals with an increased survival advantage

This paper is the first to come of our work on Drosophila. It has been led by graduate student Tyler Douglas in collaboration with chemist Richard Fitch (Indiana State University) and two students from his lab (Callie Gernand & Brianna Nirtaut), as well as NSF REU student Sofia Beskid who visited the Tarvin lab in summer 2021, and UC Berkeley undergraduate Kristen Tamsil who helped me run early experiments at the very beginning when the lab was just getting started. I'll add that we could not have done these experiments without help learning wasp and fly care from Kirsten Verster, Jess Aguilar, Marianthi Karageorgi, without the kind donation of wasps from Todd Schlenke and flies from the DSPR (Stuart Macdonald), as well as discussions with Noah Whiteman.

We are excited to share our lab’s first paper on chemical defenses in Harlequin toads, along with an excellent press release from UC Berkeley featuring Maria Jose!

Becca’s commentary on a beautiful paper by the Bellono lab is now live! Read the commentary here or find a copy of the pdf on the publications page. The study was also highlighted by the New York Times here.