Category Archives: science

Notes from the field: What’s Chris doing to that Joshua tree?

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Joshua tree, diverged. Photo by jby.

Cross-posted from Nothing in Biology Makes Sense!

ResearchBlogging.orgMy postdoctoral research is shaping up more and more to be hardcore bioinformatics; apart from some time spent trying to get a dozen species of peanut plants to grow in the greenhouse as part of a somewhat long-shot project I’m working on with an undergraduate research associate, I mostly spend my workday staring at my laptop, writing code. It’s work I enjoy, but it doesn’t often give me an excuse to interact directly with the study organism, much less get outdoors. So, when Chris Smith dropped the hint that he could use an extra pair of hands for fieldwork in the Nevada desert this spring, I didn’t need a lot of persuasion.

Chris is continuing a program of research he started back when he was a postdoc at the University of Idaho, and which I contributed to as part of my doctoral dissertation work. The central question of that research is, can interactions between two species help to create new biological diversity? And the specific species we’ve been looking at all these years are Joshua trees and the moths that pollinate them.

Joshua trees, the spiky icon of the Mojave desert, are exclusively pollinated by yucca moths, which lay their eggs in Joshua tree flowers, and whose larvae eat developing Joshua tree seeds. It’s a very simple, interdependent interaction—the trees only reproduce with the assistance of the moths, and the moths can’t raise larvae without Joshua tree flowers. So it’s particularly interesting that there are two species of these highly specialized moths, and they are found on Joshua trees that look … different. Some Joshua trees are tall and tree-ish, and some Joshua trees are shorter and bushy. Maybe more importantly for the moths, their flowers look different, too.

Joshua trees, diverged. Photo by jby.

Here’s a photo of two of those different-looking Joshua tree types, side by side in Tikaboo Valley, Nevada. Tikaboo Valley has the distinction of being the one spot where we’ve found both of the tree types, and both of the pollinator moth species, living side by side. That makes Tikaboo Valley the perfect (well, only) place to figure out whether there’s an evolutionary consequence to the divergence of Joshua tree and its association with two different pollinators. Do Joshua trees make more fruit, or fruit with more surviving seeds, when they’re pollinated their “native” moths?

So, over several years of work at Tikaboo Valley, we’ve been edging towards answering that question. We’ve found evidence that, given access to both tree types, the two moth species spend more time on their “native” tree type, and have more surviving offspring when they lay eggs in “native” flowers. But to determine whether plant-pollinator matching matters to Joshua trees, we’d really like to find out what happens when each moth species is forced to use each type of tree, and that’s what Chris has been working on for the last several field seasons.

Installing a Joshua tree chastity device. Photo by jby.

The method for the experiment, developed after some false starts, goes like this:

  • Find Joshua trees with flowers that haven’t opened yet—untouched by pollinating moths;
  • Make sure said flowers are far enough off the ground to be out of reach of the open-range cattle that graze all over Tikaboo Valley;
  • Catalog the tree, measuring how tall it grew before it started branching (a good indicator of which type of tree it is), and its total height, and take a nice photo of it with an ID number placed nearby, for handy future reference;
  • Seal up the not-yet-open bunch of flowers inside fine-mesh netting, to keep moths out—and also, as we’ll see below, to keep moths in;
  • Cover the netted flowers in chicken wire, to keep out all the desert critters that like to eat Joshua tree flowers, even if said flowers are served with a side of netting;
  • While the flowers get closer to opening, go collect some yucca moths, which you do by cutting down clusters of open Joshua tree flowers, dumping them into a bag or a cloth butterfly net, and sorting through the flowers looking for fleeing moths, which can be guided into plastic sample vials—these moths don’t usually like to fly; and finally
  • Open caged flowers, and insert moths.

By introducing moths of each species into flowers on each variety of Joshua tree, we’ll be able to see whether trees with the “wrong” moth species are less likely to make fruit than trees with the “right” moth species; and directly verify that moths introduced into the “wrong” tree type have fewer surviving larvae than moths introduced into the “right” tree type.

Camp Tikaboo, 2012 edition. Photo by jby.

But, being desert plants, Joshua trees aren’t prone to making much fruit even under ideal conditions. After a dry winter (like this last one), it can be hard to find any flowering trees at all. So to obtain a respectable sample size takes a lot of folks—this year, I was one of ten people on the field crew camped in the middle of the valley: a cluster of tents grouped around a rented recreational vehicle, which served as a kitchen/gathering area/lab.

Chris’s lab tech, Ramona Flatz, kept the whole show organized, dividing us into teams to scout for trees with flowers, teams to follow up on scouting reports and install experimental net/cage setups, and teams to go collect moths to put in the cages. This planning was, naturally, conducted in a tent containing a table with laminated maps of the valley, and this tent was called, naturally, the “war tent.”

In the “war tent,” making plans. Photo by jby.

What results we’ll get remain to be seen; this is the second year with a substantial number of experimental trees, and we won’t know whether all that work has borne fruit until Chris returns in a few weeks to see whether any of the experimental trees have, er, borne fruit. As far as I’m concerned, it was wonderful to return to an old familiar field site, in the middle of the desert, and spend a few days hiking around and harassing yucca moths instead of anwering e-mail. But if the experiment works, the results should be mighty interesting.

Below, I’ve embedded a slideshow of all the photos I took over a few days at Tikaboo Valley—including a special moth-themed production number coordinated by Ramona.◼

References

Godsoe, W., Yoder, J., Smith, C., & Pellmyr, O. (2008). Coevolution and divergence in the Joshua tree/yucca moth pollination mutualism The American Naturalist, 171 (6), 816-823 DOI: 10.1086/587757

Smith, C. I., C. S. Drummond, W. K. W. Godsoe, J. B. Yoder, & O. Pellmyr (2009). Host specificity and reproductive success of yucca moths (Tegeticula spp. Lepidoptera: Prodoxidae) mirror patterns of gene flow between host plant varieties of the Joshua tree (Yucca brevifolia: Agavaceae) Molecular Ecology, 18 (24), 5218-5229 DOI: 10.1111/j.1365-294X.2009.04428.x

Yoder, J., & Nuismer, S. (2010). When does coevolution promote diversification? The American Naturalist, 176 (6), 802-817 DOI: 10.1086/657048

Science online, busy week edition

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Hyena. Photo by redsea2006.

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Science online, perverse incentives edition

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Photo by Arthur Chapman.

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Nothing in Biology Makes Sense: You are coevolving in another dimension …

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Photo by Thomas Hawk.

This week at Nothing in Biology Makes Sense!, Devin Drown walks us through a cool new theoretical model that shows how hosts and prey species can evade parasites and predators in an ongoing coevolutionary struggle—if they each coevolve in multiple dimensions.

Instead of treating a coevolutionary interaction between two species as the interaction of only two traits, the authors investigate the nature of an interaction among a suite of traits in each species. It’s not hard to think of a host having a fortress of defenses against attack from a parasite with an arsenal loaded with many weapons.

Full disclosure: Scott Nuismer, one of the coauthors on the new model, has collaborated with me and with Devin. For more detail, go read the whole thing. ◼

Carnival of Evolution, March 2012

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Erodium cicutarium. Photo by jby.

I completely failed to submit anything to the most recent edition of the Carnival of Evolution, but fortunately I was the exception, not the rule—the monthly compendium of online writing about the complications and implications of evolutionary biology is online over at Synthetic Daisies. This edition features a nifty phylogenetic organizing framework, and a crossword puzzle. Go check it out. ◼

Nothing in Biology Makes Sense: Making sense of “stinkbird” gut microbes

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A hoatzin. Photo by Carine06.

I was off the grid last week, so I missed Sarah Hird’s latest post at the group blog Nothing in Biology Makes Sense!, discussing a cool new study of the microbes in the guts of hoatzins, a species of wonderfully weird birds.

The hoatzin has an enlarged crop for the purpose of fermentation (see figure below). A “crop” is an anatomical structure in throat of some animals (including most birds) that primarily stores food. In the hoatzin, however, it does much, much more. Foregut fermentation is a digestive strategy where microbes living in or before the stomach break down vegetation for their host. Microbes are required by foregut fermenters because only the microbes are capable of breaking down the cell wall of plants, a barrier that confines most of the nutrients found in plant cells. The hoatzin is the only bird to use foregut fermentation and is the smallest known foregut fermenter.

To learn what the new study reveals about the diversity of microbes in hoatzin foreguts, go read the whole thing, including the evolving plans for follow-up experiments in the comments. ◼

Science online, paper in your hot dog edition

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Hot dog. Photo by stu_spivack.
  • Two plus two may equal five, depending on what you’re counting. A series of thought experiments explain why in statistics, numbers need not add up.
  • Because of course you were curious. The anatomy of alligator erections, explained.
  • In other news, too much food is bad for you. Deborah Blum puts the recent study linking red meat consumption to risk of death in context.
  • Teamwork! Pesticides aren’t the sole cause of honeybee colony collapse—but they interact dangerously with other stresses.
  • But less likely to be journal editors. Hmm. Women are less likely to turn down requests for peer review.
  • And how to cultivate better ones. Author Charles Duhigg tells Steve Silberman how to break bad habits
  • Unnatural history. A new kind of museum showcases animals that have been modified by humans.
  • My baloney has a first name/ It’s P-A-P-E-R. A new form of processed cellulose—the same plant fibers used to make paper—could replace saturated fat in foods like hot dogs.

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Nothing in Biology Makes Sense: Making sense of the evolution of language

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The language of evolution. Photo by CharlesFred.

This week at the collaborative blog Nothing in Biology Makes Sense, guest contributor James Winters describes the considerable inter-relationships between evolutionary biology and the study of human language.

Darwin recognised, along with several other linguists of the period such as August Schleicher and Mikołaj Kruszewski, that language falls under the remit of evolutionary principles. Since then, there has been a renewed and growing interest in evolutionary (Croft, 2000) and ecological (Mufwene, 2000) theories of language change, with biological, cultural and linguistic forms of evolution being captured by the more general rubric of Complex Adaptive Systems. … it is the capacity to evolve and adapt that differentiates language and biology from these other systems, with the key concept being their ability to learn: past experiences filter through, or influence, future states of the system due to cumulative amplification dynamic (Deacon, 2010).

To find out more, go read the whole thing. ◼

Science online, endogenous cannabinoids edition

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Running! Photo by andronicusmax.
  • If you’ve got ’em, use ’em. Eels’ comparatively complex lifecycle may be made possible by extra copies of key developmental genes.
  • Yes, it’s real. No, we don’t know why. What science knows—and what it doesn’t—about the runner’s high.
  • I don’t think I’d call any crocodilian snout “dainty,” though. The shapes of an alligators’ and crocodiles’ snouts don’t make a difference for the strength of their bites.
  • Alas, it won’t produce flour ready-made for Girlscout cookies. Wheat engineered to carry and express genes from mint could repel aphids.
  • As if you needed an excuse to build a robotic squirrel. The purpose of ground squirrels’ rattlesnake-repelling tail-waving, tested using a robotic squirrel.
  • Because, as we all know, humans stopped experiencing natural selection 20,000 years ago. Is it possible that human speech and music are purely products of cultural evolution, instead of natural selection?
  • Less obviously, that is. Fruit flies left to evolve in complete darkness for 1,400 generations change less than you might think.

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Nothing in Biology Makes Sense: Cardiothoracic surgery

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Photo by akeg.

This week at the collaborative science blog Nothing in Biology Makes Sense, my brother Jon, a third-year med school student, describes his experiences helping out with open-heart surgery:

I stood on the other side, holding the still-beating heart out of the way. I couldn’t help but be amazed at the calm at which they did this, as if this were a perfectly normal and ordinary thing to do. Then, once all the lines were in place, a clamp was placed on the aorta, completely isolating the heart from the circulation of blood in the rest of the body. At this point, the heart is cooled down with ice and infused with a solution that arrests it in the phase of contraction called diastole. This is when the timer starts: From this point on the surgeon can operate for up several hours without any damage occurring to the heart.

For all the (not actually very gory) details, go read the whole thing. ◼