ECR Spotlight – Rachel Thayer Free

Rachel Thayer

Describe your scientific journey and your current research focus

As a small kid, I was lucky to live a 15 min walk away from a zoo and visit often. My mom made a little book for me to add to each visit by filling out all the details about another animal's habitat, diet, etc., from the signs on their enclosures and my observations. This launched my fascination with animal diversity and imagining what life is like for animals, which naturally grew into being drawn to evolutionary biology. I suppose I think of studying adaptation as focusing a lens on what it means to be alive, by sifting out what really matters to all the other forms of life around me, and why.

How would you explain the main message of your Review to a member of the public, and how would you explain the broader impact of research in this area?

Butterflies (and other animals and plants) make color in two major ways. First, they can use pigments: chemical molecules that absorb light. Familiar examples are melanin and chlorophyll. Alternatively, they can use structural color, which is the same phenomenon that makes iridescent colors in soap bubbles. This is where light is reflected and refracted by really tiny (submicroscopic) structures that bias which colors of light get reflected to the viewer. Butterfly wings have a particularly impressive diversity of these ‘optical nanostructures’. Here, we pulled together all historical reports that describe any optical nanostructure in any butterfly species, to look for bigger patterns. The main findings of our meta-analysis could be simplified to statements like ‘nanostructure type A makes a lot of different colors in different species, but type B nanostructures only make blue–green’, ‘only butterflies in the family Lycaenidae make type C nanostructures’ and ‘hey, so far none of us has gotten around to checking for nanostructures in this huge Hesperid group of butterflies that has thousands of species – so that's the next place we should look for a chance at finding something really novel’.

Is there anything that you learned while writing this Review that surprised you?

For some time now, there has been a general intuition that there is some special association between blueness and structural color – it's even been the topic of popular science media (e.g. https://www.npr.org/sections/health-shots/2014/11/12/347736896/how-animals-hacked-the-rainbow-and-got-stumped-on-blue). However, there's not much primary scientific literature that one can refer to, to really prove whether blue is quantifiably more likely to be produced by structural inference effects than by pigments. I had personal experience picking a blue animal when designing a study that I hoped would find an optical nanostructure, solely because it was blue, and I figured that similar motivations might underlie a lot of historical specimen selection, leading to biased sampling. Add that perspective to a tendency for stubborn skepticism, and I really doubted whether structural colors aren't similarly common for all the visible colors. So, in a strange, backward way, I was surprised at just how well the connection between blueness and structural color held up, even though this is probably the least surprising result of the whole meta-analysis for everyone else. That said, I still would love to see more work using strategic sampling to prove where the structures are absent.

What was your approach in organising background material and shaping this Review?

A giant spreadsheet! This was my pandemic project – my plans for lab research were frustrated, so, might as well read and try to synthesize hundreds of papers.

What do you see as the main value of Review-type articles?

Especially as an early career researcher, I appreciate reviews that provide an accessible welcome into the field for newcomers, a guide to the literature. Reviews can also synthesize existing research to make broader patterns and knowledge gaps clear, so they can sometimes even give experts a new perspective.

Are there any important historical papers from your field that have been published in JEB?

It's really not old enough to be called ‘historical’, but Stavenga et al.’s 2014 paper ‘Coloration principles of nymphaline butterflies – thin films, melanin, ommochromes and wing scale stacking’ (doi.org/10.1242/jeb.098673) is a JEB article that influenced my dissertation work very much. Everyone loves the morphologically elaborate nanostructures, and most of the papers I found as an early grad student focused on these, which didn't help me understand my own blue butterflies. This study did such a great job of thoroughly sorting out how color works in the morphologically simplest butterfly scales, explaining the contributions of pigments and both surfaces of the scale, and integrating several different types of measurements with theoretical modeling. I referred to it constantly.

What do you think experimental biology will look like 50 years from now?

One thing that excites me is the continually growing toolbox for experimental research in classically non-model species – advances such as cheap, high-throughput genomics and CRISPR-Cas9. This is exciting because it can help us take advantage of millions of years of naturally evolved ‘experiments’ that explore the possibilities available to life on Earth – we can increasingly design incisive studies of whichever organisms evolved the most compelling, most extreme examples of any biological functionality that piques our curiosity. We might come to regard the next 50 years as the era of non-model system genetics research. That's my optimistic answer. Another prospect is that in the next 50 years, opportunities for experimental biology will be eclipsed by the extinction, climate and human displacement crises.

If you had unlimited funding, what question in your research field would you most like to address?

No experiment I could possibly design today is more valuable than preserving the opportunity to pose a new experiment tomorrow, next year, or in a decade. My cohort of scientists has come up inspired by imagining what it was like for contemporaries of Darwin to encounter and compare global wildlife, or during the modern synthesis, as the invisible internal mechanisms of evolutionary genetics unfurled. Now, we stare down the prospect that, during our turn, we will have to watch the biosphere die. I have peers who set out to study ancient mass extinction events only to find that the conditions that precipitated ancient mass extinction events aptly describe events now. I have contemporaries who set out to discover new species by recording sounds in the rainforest, only to capture an eerie transition toward silence. I've done very little field work and I study hardy, laboratory-tractable species that aren't endangered or picky about where they live, but even I stopped finding butterflies at my best collection site after wildfires. In my 10 years in science, I think I've never been to any research conference, on any topic, without hearing my colleagues interject dire warnings into their presentations – and I've never attended a climate-focused conference. So, the most important research question is ‘will the species I hope to study – and a stable international society that can support research activity as I've known it – survive the next 50 years?' With that in mind, with ‘unlimited’ funding, the best thing I can imagine doing for science is to fight. I think of legal support for climate protesters; cultivating honest communication platforms that bypass corporatized media; criminalizing ecocide; eliminating fossil fuels fast; protecting democracy against regulatory capture; buying out and defending the recommended 30% of Earth's surface as nature reserves; facilitating socially just transitions to safely support humans in the remaining land.

What's next for you?

Now that my paper has just been accepted by JEB? My dog thinks we should close the laptop for a bit and go on an adventure.