I’m going to the mojave this summer!


This is where I'm spending my summer vacation. Bleak, ain't it?

This is where I'm spending my summer vacation. Bleak, ain't it?

As my inaugural post (other than my old Collegian articles) I’m going to gloat a little. I just got accepted to work with one of my biology professors this summer as part of Willamette’s Student Collaborative Research Program (SCRP). SCRP pays professors to take on students as research assistants and students to do research. (I’m getting $4000, plus food and housing stipends, compared with the ~$3000 most other programs give.) My team (Professor Chris Smith, a freshman biology student, and me) are going to be studying two aspects of Joshua tree (Yucca brevifolia) ecology. We’re going to Tikaboo Valley (which happens to be right next to Area 51) for three months after classes end, and then we’ll spend about a month and a half in the lab. We’ll present our results to everyone at Willamette, and then head down to Gonzaga in November for a conference.

The first project, which I’m probably not going to be doing much work on, concerns Joshua tree pollination. Like all Yuccas, Joshua trees are pollinated only by the Yucca moths Tegaticula synthetica and T. antithetica. These moths deposit a pollen ball on the flower’s stigma, and then lay their eggs in the ovum next to the ovules. The caterpillars feed on some, but not all, of the developing seeds (if too many eggs are laid, the fruit won’t develop at all). The moths’ ovipositor is blade-like to cut into the ovum, and needs to be matched to the thickness of their host’s ovum wall: too short and they won’t make it through, too long and it can damage the flower, causing it (and the larvae) to die. Given this, there ought to be coevolution occurring between the two species. We haven’t discussed our research questions yet, but the other student researcher will be looking at this system, which is fascinating. I’d be jealous if it weren’t for my topic.

The topic that I’m probably going to be focusing on is the possible effects of climate change on Joshua tree conservation. The Joshua tree is fairly picky about its environment, and climate models have predicted that it will suffer quite a bit under the impacts of global warming. The problem is that those models assume that wherever there are currently Joshua trees, the habitat is suitable for Joshua trees. This might not be the case, however. Joshua trees were affected fairly significantly by the warming after the last ice age, and their range basically forced them up mountains. It seems like they’re still moving, since there are only young trees in the upper limits of their range and only old trees (and I mean old — they can live for hundreds of years) at the bottom. So we’re going to see if their range has been expanding or contracting.

Unfortunately, this is more difficult than it seems. We’re looking at trends from before records were kept. We’re going to start by trying to determine population structure at different elevations: if old trees predominate, the population is shrinking; if young trees predominate, the population is expanding. Unfortunately, we can’t just take core samples (that would be too easy). Joshua trees are monocots, and don’t put down annual growth rings like most trees. (Actually, they have an internal secondary meristem that grows inward, unlike most trees that grow outward.) So we have to use morphological traits like height, number of branches, and a few others. Unfortunately, the trees will grow at different rates depending on temperature, rainfall, and nutrient availability. We can try to adjust for this by confirming our results with radiocarbon dating, but that’s expensive (on the order of a couple thousand dollars per tree), so we can’t do it on as many trees as we’d like.

We’re also going to try some population genetics. There are a whole bunch of genetic signatures of population expansion and contraction. The most widely used is heterozygosity. When populations decline, both allelic richness and average heterozygosity fall. However, because of math that I don’t understand they decline at different rates, leading to heterozygote deficiency. Various programs take advantage of this to crunch genetic data and detect bottlenecks. Other programs use coalescent theory, which takes advantage of the fact that genetic drift takes place at faster rates in smaller populations to calculate the size of populations in the past.

So, in summary, I’m psyched, lots of cool science, and I’m going to bed so I can make it to Organic Chemistry in the morning.

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