Physiological tolerance (or lack thereof) as a tool

The Park Service ranger called my cell phone three times in ten minutes. He was concerned about my safety of myself and that of my field assistants, noting that my car was still at the trailhead to my research site at 4pm, and temperatures were well into the triple digits.

Blazing hot volcanic rock on a south facing slope on a clear June day
Blazing hot volcanic rock on a south facing slope on a clear June day

In fact, we had knocked off earlier than I had planned and were already hiking back, because despite setting up a tarp as a scenic shade ramada, and my constant encouragement to drink more water and more Gatorade, we were overheating.

This was a far cry from my last week, when I attempted to climb Mr. Rainier. With a peak at 14,411 feet and sporting the largest glaciers in the lower 48 states, this mountain tested some very different physiological tolerances. Certainly the 1:30am start was cold, and I wore a layer of wool covered by 1-2 layers of fleece, covered by a wind-proof shell over virtually all part of my body. Plus during breaks I added a down jacket over it all.

Our lack of ability to withstand heat may have to do with a trade-off for performance in a wide range of temperatures, including environments with year-round snow.
Our lack of ability to withstand heat may have to do with a trade-off for performance in a wide range of temperatures, including environments with year-round snow. Photo by Neill Prohaska

But cold was not the only physiological challenge on the mountain. Ultraviolet radiation is more intense because it has less atmosphere to pass through, and is reflected off the snow in every direction. The first day I only put on sunscreen once, and my face was badly burned.

All bundled up to withstand the radiation and cold
All bundled up to withstand the radiation and cold. Photo by Neill Prohaska
Bundled up on a 3am break. Maybe we should start research in the Sonoran Desert at that time, too? Photo by Neill Prohaska

Additionally, the low air pressure and corresponding low oxygen levels present physical challenges in acclimatization and physical exertion. One member of our party started coughing up bloody sputum, which may or may not have been indicative of his having high altitude pulmonary edema (HAPE), a potentially fatal condition. HAPE is, interestingly enough, may stem from the body’s evolved response to fungal infections.

So what a relief to return to the balmy lower latitudes and altitudes, right? Highs are well over 100 degrees Fahrenheit in Tucson, though, and my research revolves around low-elevation (hot), south-facing (hotter) slopes covered in dark volcanic rock.

But the problem of my field crew’s physiological tolerance not withstanding the Sonoran Desert summer is also a solution for an experimental annoyance. Bruchid beetles lay their eggs inside paloverde seeds. Last year, I had gathered a number of paloverde seeds to use in germination and seed removal experiments. Beetles decimated my stores, emerging from up to 75% of the seeds and attacking the rest inside my insect-proof bags.

In the last year, an accomplished naturalist mentioned the observation that those seeds falling outside the shady crown of a parent tree survive better, perhaps because the direct sun kills the beetle larvae. Their lack of physiological tolerance to the direct sun can be used against them. So I am drying the first gathered seeds on my roof:

Drying paloverde (Parkinsonia microphylla) seeds on my roof to kill bruchid beetles lurking inside
Drying paloverde (Parkinsonia microphylla) seeds on my roof to kill bruchid beetles lurking inside

It’s about time, you two!


Making more water striders


My water striders (family Gerridae) have been mating like crazy. Like, for 8 hours one day. I wasn’t there the whole time, but I suppose it’s possible they didn’t even stop. Given our differences in lifespan, that scales (very) roughly to about a solid month for us without getting out of bed (8 hours times 100 strider life spans is 33 days). Only they’re cruising around on top of the water the whole time.

And finally, finally… I gazed at the surface of the water Monday, deep in thought about something else entirely, and I sat up a little straighter and asked myself, “What is that?”

It was a tiny little blip and that blip was moving. Moving like it was hopping. In tiny little hops.

I eventually discovered not one, not two, but four baby water striders in my tank! I imagine they lay more than four eggs at a time (many insects do), so I wonder what happened to the rest of them. Maybe the backswimmers or even their own parents had some easy snacks over the weekend as they hatched. It happens.

In the meantime, I have moved the blips over to their very own kiddie pool, given them some rocks and some sticks and leaves to hide in. It looks much lovelier to me without the murky algae, but maybe they find the clear sterility of the water unpleasant. It would be an interesting hypothesis to test, allowing them to chose between habitats.


The kiddie pool.


What am I doing raising aquatic insects in my hidden underground laboratory? (Besides being creepier than just having a hidden underground lab?) I may have mentioned my research interest once or twice: biodiversity. Specifically, why we have so much of it to start with. I may also have suggested I am currently working on a theoretical research project which has been a real challenge and taught me a lot.  The basic question of it is: does hiding from a predator effect whether two competing species can live together?

I’ll explain more about the framework and the techniques later, but I’m thinking about how to test it in real life, and I am thinking about aquatic insects (after all, they are little, with short life spans, relatively simple neural networks, etc.). I posted already about my field trip with another student to count the backswimmers and water striders in pools on Mount Lemmon, and to collect them (yes, we have a Forest Service permit for both). I have kept a few, just to observe their behavior and formulate intelligent (well, I hope) hypotheses. That’s these guys. And now there are more of them. I’m so proud.

Step 1 to being America’s Next Top Biologist

Excerpt from my field journal.

Being a respected biologist these days usually requires a little more training than natural historians of the past would have encountered. We have to learn stories at the molecular and cellular levels, up through what we can touch and feel and see, and above to the population and ecosystem levels. There are statistics and politics and grant writing skills.

But I propose that Step 1 to being America’s Next Top Biologist is to keep a field journal. This is hardly an original idea. Most biologists in the past did so, and most do today. Charles Darwin, arguably one of the most famous biologists ever, published his field notes as a book titled The Voyage of the Beagle. It is full of maddeningly narrow-minded commentary, especially at first, but it is a fascinating read about an adventure and a world that today we can only approximate.

I have one quibble with Darwin’s journal, too, which is the lack of drawings included. I suppose he may have done them, and just not have included them in the final version. I can commiserate. I’m more than a little embarrassed about the quality of my field journal drawings.

But the point of field drawings for a biologist is not just the aesthetic quality of the finished image. It is the process of looking more closely at a plant or animal. It is the difference between noticing or missing that every flower on this plant has five petals, or that something has been chewing on the leaves.

All our fancy statistics and abstract theory come to very little use without the details of what is happening, and being done by whom and how and where in the natural world. To be a big picture thinker, you still have to remember to look at the details once in a while. And there is no better time than while watching bugs in your classroom, strolling around your neighborhood, or backpacking through remote and wild territories. It’s something everyone can do, whether or not you are a professional.

I’ve shared a few images of my journal here. I mostly included the pictures because they’re more interesting to look at than my hurried handwriting. In the trade-off between being more organized and being more accessible, I tend to the immediate and hence lack some recording detail and standard format. That’s something I might work on.

Do you keep a field journal? Who knows, you could be America’s Next Top Biologist. What have you recorded lately?

That’s it

What if your life and your children depended on living in water, but every so often the pool you were living in dried up? Maybe it was no more than a puddle, and, though part of a flowing stream after every good rain, between storms just disappeared – sometimes? Let’s say you’re an insect, and you have wings to fly off in search of other water, but your offspring won’t for a month or two. Why would you ever lay your eggs somewhere so risky?

In my last post, I wrote about how the landscape we live in, even a city block, is full of good patches and bad. What makes a spot “good” or “bad” to a dandelion or a dragonfly depends on their individual needs: a dragonfly needs water and plants to land on and other insects to eat, while a dandelion needs soil and light and of course some water, too. But the number of other conspecifics (other dragonflies or dandelions) they have to compete with can also make a patch better or worse.

Galen catches something in one of his larger pools.

Besides wanting to understand life, the universe, and everything, I want to be a biologist because I like being outside. So I was excited to help another student in my lab with field work last week. Galen studies stream ecology on Mount Lemmon, the tallest mountain overlooking Tucson in the Santa Catalina range to the north. Specifically, he studies the response to environment and competition in several kinds of aquatic insects. That sounds like a mouthful, so I’ll just summarize that he counts backswimmers and water striders up and down these mountain creeks.

I am planning to study these communities of aquatic insects, too, because they are crazy cool. First of all, they have short life spans compared to a PhD timescale (a few weeks to a few years), and are really small, and live in small little pools, so it’s easy-ish to study their population dynamics. Well, easier than studying lions and hyenas on the African savanna anyway, since I can just box these guys up in a kiddie pool or aquarium and watch to see what happens.

Backswimmers in Tupperware
Backswimmers (Notonectidae, 1-3 different species pictured here) waiting to be identified and counted
The round things clinging to the rocks below the pine needles are the males of the giant water bugs (Abedus herberti), who carry a raft of eggs on their backs until they hatch. The proud new daddies refrain from eating for about a week, then even their own young are fair game as prey for these voracious predators!

But if you get down on your hands and knees, these guys are no less spectacular than crocodiles and elephants. You ever have backswimmers invade your pool? Did they bite you? They haven’t gotten me yet (I scoop them up in a net and let Galen do the handling), but I hear the notonectids (science-y name for backswimmers) pack a punch that’s not as teeny tiny as they look. Then there are the “toebiters,” also known as giant water bugs, like Abedus herberti (that last year’s Biosphere 2 fellow Chris Goforth studies and blogs about here). Brilliantly colored sunburst beetles (Thermonectus marmoratus) bustle around the rocky beds of these glorified puddles. What is their business? What are they eating? Above them, water striders (Gerridae) skim the surface.

Underwater photo of sunburst diving beetle (Thermonectus mamoratus)
Two water striders (Gerridae) that have been marked white and blue to indicate the pool they were captured in. Just below and to the left of the bottom one, you can make out a backswimmer lurking beneath the surface - the striders better watch out!

Beyond the alien-like life forms fighting their daily battles in the pools, liquefying and sucking the guts out of one another, these streams perfectly illustrate the variability I wrote about last time. While after a good rain, water cascades over the Gneiss bedrock like designer waterfalls, most of the time it seems these “streams” dry up into a series of puddles. Some are the size of a hot tub, while others are hardly larger than a pot you would boil spaghetti in. Some are shaded by trees, others bake in direct sunlight, surrounded by bare rock radiating heat back. (Those are absolutely unbearable to count bugs in on a hot summer day, even at the higher elevation.) Some are full of fallen trees, grass, or algae, and others are nearly empty.

But these pools also change from week to week, from year to year. Last year, Galen picked a bunch to monitor, counting the insect inhabitants regularly. He tried to pick some that he thought were permanent, and some that were ephemeral, or dried up entirely rather frequently. (Note for geeks: he did this by dividing all the pools into these categories of permanence and elevation, then randomly selecting a percentage of each of them using a computer random number generator I think. That’s called a block design. It’s very important to prevent researcher bias in experimental design by doing things like flipping coins or using random numbers. Human beings are inherently nonrandom, however random, say, your parents may seem sometimes.)

This year, however, the pools are behaving totally differently. Pools that were always dry last year now boast water after weeks without rain. Ecologists call this spatio-temporal variability, and it can help promote coexistence, just like the spatial variability I wrote about in the last post, although as you can imagine, it gets more complicated when you consider that fourth dimension (time). Spatio-temporal variability and its effects on community structure is what my adviser specializes in, and it’s the title of the class I am taking from him this fall.

So why risk the variability when you could opt for a more consistently safe environment? Maybe it’s a case of high risk bringing high reward. A small pool may dry up, but if it lasts, your offspring may have it all to themselves, low competition, low predation. For species with buffered population growth (a relatively long adult lifespan, or a seed bank, or something else that keeps them around), a good year can help more than a bad year hurts. That’s one condition for the storage effect my lab studies. Hopefully Galen can enlighten us in the next couple years about what’s really going on with these pools.

A small garter snake chills out in a bedrock pool on Mount Lemmon.