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  • Andy Davis

A zoom conversation with Elise Zipkin about monarchs and climate

Hello everyone,

I'm excited to tell you about today's blog entry, which delves deep into a brand new study about monarchs that was published in a very, very prestigious journal. The paper, titled, "Changes in climate drive recent monarch butterfly dynamics" was published in the journal Nature, Ecology and Evolution. It was authored by Dr. Erin Zylstra and colleagues. Erin is a postdoc in the lab of Dr. Elise Zipkin, at Michigan State University. Here is a link to the new paper, although it is not downloadable.

Some readers may have seen a few headlines here and there referring to this new paper. Here is one in Popular Science.

I've known Elise for many years and I have always been a fan of the work of her and her lab folks. Though, I have to admit that this type of analytical research is not my forte, so, for this blog, instead of me trying to write about the paper, I decided to go straight to the source, and to record a zoom conversation with Elise where we talked about this new project. Unfortunately, Dr. Zylstra was away. Regardless, Elise was able to fill me (and you) in on the details of the project, and I shared my screen during the conversation too. That way, folks can at least see the critical figures in the paper.

So, below is the conversation we had. I did my best to bring to conversation down to an easily-digestible dialogue when possible, although I might have failed at some parts, where we get into the weeds of the statistics!

The conversation lasts about 45min, so get yourself a cup of coffee, or glass of wine, strap in, and listen to two nerdy scientists talk about monarch research...

OK folks, now that you've watched the conversation above, let's see if I can boil down the main takeaways from this conversation, and the paper.

This study used citizen science surveys of butterflies (but only using the data for monarchs), in the American Midwest to determine how climate (temp, precipitation) during the spring or summer affected monarch abundance, and whether the climate factors outweighed others like amount of cropland, amount of roundup used, or fall nectar availability.

Results showed that spring climate was the most important factor, followed by summer climate, which both influenced how many breeding monarchs there are in any given year. Climate was also more important than was how much cropland there was around a survey site, or how much roundup was used in the county around the survey site.

The biggest influence on the winter colony size was the summer population size (and by extension, the spring and summer climate). This summer climate effect was more important than was the greenness of the fall flyway (which oddly, goes against a prior study from this same lab).

So in a nutshell, climate matters a lot to monarch abundance. This is actually something that a lot of other researchers are finding too. Recall the recent paper by Matt Forister and colleagues, who showed how climate in the American west is severely diminishing the number of butterflies (all species). I talked with Matt about that study too.

One of the final points we talked about was one interesting finding from this study regarding the winter colony data. Their results showed that the size of the winter colonies has very little influence on how many monarchs end up in the breeding population each year. This is something that this lab group has found in prior studies too. This led to an interesting philosophical discussion over whether the colony size matters (statistically). Not sure if we resolved this!

Anyway, I hope this blog was useful for breaking down this new paper. Kudos to the authors for this accomplishment.

That's all for now.


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The science of monarch butterflies

A blog about monarchs, written by a monarch scientist, for people who love monarchs

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