How does hiding from a predator affect biological diversity?

Ecosystems, and the biological diversity they harbor, are complex things. Yet simple mathematical models can often capture important features and teach us about their dynamics.

You might once have learned about food chains in school. For example, plants producing energy from the sun are eaten by rodents which are preyed on by owls. That’s a food chain with three links. Because just about everything has some kind of predator or parasite or other natural enemy, and just about everything must compete for resources of some kind, let’s focus on the middle link in this chain.

To study how many species can be supported in a middle link of such a chain, think first of two species. If each one can invade the system with the other species present, they can coexist. A simple model proposed early in the 20th century by Alfred Lotka and Vito Volterra can be solved for when two species would coexist, increasing biodiversity.

But this model leaves out a major piece of how animals function in the world around them: behavior. What if both kinds of rodents learn to hide from the owls under plants? Does it make them more or less likely to coexist?

In research I did with my doctoral adviser, Peter Chesson, published online recently by The American Naturalist, we show that the answer depends on how much those animals overlap in their resource requirements, like the types of food they like to eat, and in their vulnerability to different predators. When both prey can avoid predators, if they need exactly the same types of plants to survive and ground to dig their burrows, one may drive the other extinct. But if they are more different ecologically in their resource use than in which owls prey on them, then avoiding owls could make them even better able to coexist. (In an appendix, we even show how this scales to more than two species.)

I started this research in 2009 as a brand new graduate student, and worked on it off-and-on for the last decade. Peter’s guidance on this project taught me how to do research, and how to present it and to write about it.

You can see a plain-language summary of article here, or download the paper itself with all the equations here. Feel free to email me for a copy if you don’t have a university hook-up to access it without paying an arm and a leg.

 

Antarctica

I returned to Colorado almost a month ago now from nearly four months in Antarctica. Some of the samples the team collected from our experiment there recently arrived in Colorado separately, and the rest should arrive this week. I am settling back in to life here, answering four months of mail, getting out in the mountains on my skis, starting to extract DNA from the samples, and continuing to analyze data from field seasons past.

For detailed updates during our season, check out the project blog I kept up almost daily while on the ice (despite the slow internet).

Here are a few highlights:

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We found our experimental cryoconite holes (mud puddles on the glacier we had made in a past season)! This was far from a certainty, because our holes look identical to those that form naturally and are difficult to mark accurately without affecting their melt. An organization called UNAVCO provided invaluable help with precision GPS marking our holes, and a way to recalculate their new position – they move about 3-4 inches every day because the glacier ice under them is flowing!

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We spent a long season in the field camp, and were able to watch the progression of naturally occurring cryoconite holes. Each of the small, round depressions in the ice at the bottom of the photo above is a cryoconite hole. Notice the ones nearest have a layers of new dust that blew onto their surface after a strong wind storm. When that dust melts through the ice lid, the microbes in it will “invade” the microbial community active in the mud puddle below. Will the new microbes be able to reproduce? Or will the existing community “resist” their invasion? That is one of the questions we hope our experiment will be able to answer.

Our team connected with hundreds of students around the US by Skype to answer their questions about our research and life in Antarctic field camps. I was even able to answer questions live in a Science Riot comedy show at the Clocktower Cabaret in Denver by Skype from camp!

And we looked good doing it all ūüôā After by brother-in-law told me about the fashion insert in the Sunday¬†New York Times featuring layers of jackets as the “it” look this season (left photo above), I did my own fashion shoot on the glacier during a break from fieldwork in my 4-5 layers. Apparently I’m supposed to smile less while modeling. But I think my heals might be as pointy as the model’s.

Just a little luggage

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Photo credit: Aleah Sommers. Thanks for the ride to the bus stop for the airport bus, sis!

Well, I am planning to be in a very cold place for more than three months, and camping in New Zealand after that. The trip requires a bit of gear.

I’m headed back to Antarctica for the third and final season of the currently funded research on microbial community assembly in Antarctic cryoconite holes. Check out my previous posts on this blog for more details on life on the ice. I will try to post daily updates and photos, internet speed permitting, at www.cryoholes.wordpress.com.

And if you are a US citizen and haven’t voted yet, do it by the end of the day this Tuesday (Nov. 6th)!

It’s a girl!

A big piece of my stand-up comedy set about my research last month was about how good I am at killing tardigrades, or water bears as they are commonly known, despite their reputation for being indestructible. (They’ve survived five mass extinctions on the planet, but they can’t survive me!)

I have been trying to grow Antarctic tardigrades and their more awesome but less cute metazoan cousins, bdelloid rotifers, in petri dishes in the lab. These microscopic animals are abundant in the glacial ecosystems I use as natural test tubes to understand how ecosystems organize. They are large enough to spot with a dissecting microscope – much lower power than would be required to see individual bacteria – so I hoped they would be useful for more controlled experiments.

However, I was not initially great at keeping the little critters alive, and moreover, having them reproduce to be a population.

Since I am not an expert at tardigrade identification, I thought the best way to isolate different populations of water bears would be to create cultures from individual lineages: meaning I put a single tardigrade on a petri dish and waited for it to lay eggs.

I was fairly certain that any animal whose life plan involved getting dried up and blown into some ice, then waking up when that ice melted into an isolated puddle of water would not have to rely on finding a mate. The chances just seemed too low. The most common tardigrades in Antarctica reproduce by parthenogenesis, laying unfertilized eggs. But after a while without babies, I was starting to wonder if they needed to mate or something.

And then last week, two students working on this project found that a petri dish previously containing a single tardigrade now held three additional tiny tardigrades! Our camera situation is not so great with the petri dishes, so I held my cell phone up to the eye piece to try to snap a picture:

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That whitish cigar shaped thing with dark colors in its middle is a tardigrade. The green blobs around it are algae. The dark stuff inside the tardigrade I believe to be algae it ate!

Here is a better image of Antarctic tardigrades I took also using my cell phone, but a microscope in Antarctica:

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So I guess the tardigrade really is a “girl” – at least it laid eggs?

Stand-up science

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Thanks to Eli Weber for getting a shot of me on stage!

Ever wonder why a tardigrade is commonly called a “water bear?” Yeah, me too! I think the name is stupid – they don’t look like bears at all.

That was the start of my stand-up comedy set about my research last night, performed as the closing act to a sold-out crowd of 120 paying customers at the Denver Museum of Nature and Science.

Although my postdoctoral research is really focused on determining how random ecosystem formation is, using mud puddles on glaciers as natural test tubes, for a ten minute set of jokes I focused on the two most common animals in these mud puddles. I tried to explain why tardigrades have a reputation as being basically real-life Avengers, and why their fellow metazoans, the rotifers, which get no attention from the internet, are the real real-life superheroes of surviving space and running our home planet.

For the past several weeks, I have driven to Denver one night a week for a two-hour workshop on scripting my science interests into essentially a TED talk with jokes. It’s a workshop provided free to STEM professionals. After three weeks of two-hour meetings, they throw you on stage in front of a paying crowd! (With a cash bar, at least.) I like to think of it as a comedy “recital,” like I used to have for piano or dance lessons.

The nine of us who completed the workshop performed our sets, with a professional mentalist as an MC.

I had a great time, remembered mostly what I wanted to teach the audience, and even got a few laughs!

Ever since I found out a friend, Alex Falcone, taught stand-up comedy workshops in Portland, and that part of what he asks his students to bring to a set is to have a point, I have wanted to share the ridiculousness of my day job through jokes. Finding this workshop so close to Boulder was a dream come true.

If you work in a field of science or technology and want to tell some funny stories from your career or just teach a group of interested people one interesting little factoid about your expertise, check out whether Science Riot offers a workshop near you. If you’re not in Denver you won’t get to work with the incredible Jessie Hanson, but I’m sure they have other great people!

Shakti and the Sommers Sisters’ School Science Safari

A few days ago, a new paper was published on a subglacial hydrology model of the Greenland Ice Sheet. The name of the model is SHAKTI, which stands for Subglacial Hydrology And Kinetic, Transient Interactions. The lead author is my sister, Aleah, who developed this model as part of her PhD dissertation work. She is also a serious yogi and yoga instructor (who runs retreats in mountain huts and secluded Mexican beaches if you want to join her!).

She was tickled that her coauthors went along with the acronym, which is, in her words, “a Sanskrit term for the energy that gives form to everything in the universe, the divine feminine principle.”

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Aleah presenting her dissertation work publicly at her defense.

I was privileged to hear more about her research earlier this spring, not only at her public presentation as part of her dissertation defense, but during a series of joint presentations we did on our “polar opposite” (Arctic vs. Antarctic) research.

The presentations took place at schools in Ouray, Ridgeway, and Cortez, in southern Colorado. They were organized by the Pinhead Institute, who graciously hosted us in Telluride. It was a great few days of sister road trip adventure, sharing photos and stories and scientific results of our adventures with K-12 students (mostly high school, but a 3rd grade class or two!). We dubbed the adventure the Sommers’ Sisters’ School Science Safari as we toured between often several schools and towns in a day. Here are some images of that journey:

Hopefully Aleah’s research and the addition of the SHAKTI model will help predict future melt rates of Greenland’s ice sheet and coastal glaciers, and provide better forecasts for the speed of sea level rise. Check out this latest paper yourself – and see if you can understand any of it! If not, Aleah does a great job of explaining it in plain language in person, so ask her over a glass of kombucha, or see if she is up for presenting to your class or club.

 

Microscopes to telescopes: Back to UA Science Sky School

Last week I had the pleasure of returning to a mountain top where a not-so-little piece of my heart remains. It has been more than two years since I taught at UA Science: Sky School, a program I had piloted as a UA/NASA Space Grant Fellow starting in 2012-2014. I was amazed that despite the way the team and the current instructors have grown and improved the programs, it felt so much like going home. I loved sharing photos from my new research in Antarctica and helping students transform their cell phones into microscopes while they waited for their turn at the telescope.

This was the sixth annual trip for Flowing Wells High School, the first school to attend Sky School’s flagship four-day outdoor research experience, in which students stay in dorms at the observatory and are advised on team research projects by graduate students. The students from this Title I school are supported on their Sky School trip by a Superintendant who raises the money to fund their trip from his Rotary Club, and by teachers who organize and chaperone the four-day trip.

IMG_20180426_091420375And these students really deserve the support. The research on geology, hydrology, and biology in the national forest that they presented at the symposium the closing night of the program was impressive. They hiked for miles over thousands of feet of elevation change and learned new math and engineering skills to collect their data and design their equipment.

As the Arizona teachers wait at the capitol for a vote on a budget deal today, I hope the Governor and the Arizona Legislature understand just how much these teachers give up to support their students, but moreover, how much these students deserve more funding for infrastructure, supplies, and other pieces that make education work. I hope they find a way to raise and sustain the funding to make education not just less embarrassingly underfunded in Arizona, but a priority – not only when a walkout forces their hand, but on their own in the future.