Battle scars

It will come as no surprise to anyone familiar with the academic world that academics don’t always agree. In fact, they often engage in fierce and lengthy disagreements about topics that never cross the minds of 99% of the world’s population.

These disagreements are the foundation of good science. Good science happens when smart people with different ideas engage with each other and find ways to test those ideas. However, if you’re a field assistant for one of those smart people, those disagreements can also be a pain in the ass.

An argument between two scientists is exactly how I ended up crouching in the middle of a patch of poison oak in the California hills, my fingers stuffed in my ears, tensed in anticipation of a shotgun blast. (But it’s not quite as bad as it sounds – I promise no scientists were harmed in the making of this blog post!)

At the time, I was working in California for a professor who had been studying acorn woodpeckers for many years. Acorn woodpeckers, as their name suggests, depend heavily on acorns. In fact, groups of these birds create ‘granaries’ by drilling holes in trees (or anything else, including people’s houses) and stuffing those holes full of acorns for later consumption.

Given the tight ties between the woodpeckers and their food source, it made sense that the professor I worked for was interested not just in the birds, but also in the oak trees they relied on – in figuring out the details of how and when they produced their acorns. And this was the source of the argument I found myself in the middle of.

My boss had gotten into a disagreement with another scientist about how far oak pollen could travel. The question was whether oak trees could be pollinated only by other oaks within a relatively small radius (roughly a kilometre), or whether the pollen could travel much longer distances. The funny thing is, I honestly can’t remember which side of the disagreement my boss was on; all I know is that he had decided he was going to settle the question once and for all. How, you might ask? Well, that’s where the shotgun came in.

The logical thing to do, he had decided, was pick a focal oak tree and take a leaf sample from every other oak within a 1 km radius. Then he could sample the focal tree’s acorns and try to match them to DNA from the leaves of the putative fathers – a plant paternity test.  If he found that at least some of the acorns did not belong to any of the trees he had sampled, he would have evidence that pollen could travel farther than a kilometre.

However, this plan turned out to be anything but simple in its execution. First of all, the field station was surrounded by oak savannah.  By definition, there were a *lot* of oak trees around. Sampling every oak within a kilometre of the chosen focal tree was not a trivial task.

The landscape around the field station: rolling hills covered with – you guessed it – oaks.

Second, many of those oaks were located in…inconvenient…places, such as at the top of steep hills, the bottom of ravines, and often, the middle of large patches of poison oak. Closely related to poison ivy, poison oak is – as its name suggests – a plant better avoided. Its leaves are covered in urushiol, an oil which causes an allergic reaction in the majority of people who come into contact with it. My boss informed me that he was in the lucky minority that did not react to it. Never having encountered poison oak before this field job, I didn’t know which camp I fell into, but I wasn’t really interested in finding out the hard way.

Third, most of the oaks we wanted to sample were beautiful, stately, tall old trees. Their height was obviously an advantage when it came to spreading pollen – but a substantial disadvantage when it came to getting a DNA sample.  Plucking a leaf from a 25 m tall tree is easier said than done…which brings us back to the shotgun.

If we were unable to reach a tree’s leaves, my boss’ plan was simply to shoot a twig off. Then the twig and its attached leaves would float down to the ground, allowing us to waltz over and pick up the sample with minimal effort.

Presumably several potential flaws in this plan are obvious to many of you.  But for me, the main problem wasn’t my boss’ aim (as you might think) – but rather the noise associated with shooting our samples down. As someone with a phobia of sudden loud noises (it’s a thing, really!), I can’t even be in the same room as a balloon…so shotgun blasts are well outside of my comfort level.

Eventually, my boss and I worked out a routine. After hiking, scrambling, or clawing our way up (or down) to the tree we were trying to sample, we would circle it (often wading through swaths of poison oak) to look for any leaves within reach. If we didn’t find any, he would get out the shotgun and start sizing up targets, while I would retreat, crouch on the ground, stuff my fingers as far as possible into my ears, and wait for the bang.

By the time we wrapped up at the end of the day, my ears were ringing and my fingers hurt from spending a substantial portion of the day crammed into my ears. Shortly after getting home, I discovered that yes, indeed, I did react to poison oak.

And to this day, I still don’t know how far oak pollen can travel.

One of the oak trees that gave us so much trouble...

One of our oak ‘victims’

4 thoughts on “Battle scars

  1. the shotgun is a very guy solution 😉
    seems like a stick on a string could have worked too, toss it up into the branches and pull a leaf or so down..
    as a shotgunner your prof should have had ear protection both for himself and you ? I don’t shoot without earmuffs.. so would guess he also was not a regular shooter, or he’d have been deaf already from not using protection.. ha.

    my guess would be the pollen goes way more than a km, given the oak pollen is relatively small and light so wind could disperse it widely. A map of oak pollen allergy responses and tree locations would probably be interesting. Of course the question then is, if the pollen is sufficiently active to induce an allergy response, is it also sufficiently active to work for pollination ?

    • Yes, I would agree that a shotgun is a rather ‘guy’ solution. But while a stick on a string would have worked for some of the trees, some of them were really too tall for that approach. And it wouldn’t have made for as good a story!

  2. Hahaha! Of course I had to immediately look up how far oak pollen disperses. Without reading the papers or knowing much about differences among oak species, I found studies with very different results (a simulation study said up to 100 km, one on isolated stands in a 20 km valley said ‘surprisingly little long-distance dispersal’). However, I liked this statement from Austerlitz et al. (2007; “Estimating anisotropic pollen dispersal: a case study in Quercus lobata”, Heredity volume 99, pages193–204): “Despite the value of paternity analysis in describing the pattern of pollen dispersal, it requires a large sampling effort, involving the maximum possible fraction of the potential fathers of a given set of seeds, which makes it difficult to sample on a landscape scale […].”

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