CSUN is about as close as possible to the ideal place to do the kind of science and scholarship I want to do — a large, diverse public university with strong support for teaching and research, and great colleagues studying ecology, evolution, and every aspect of the living world. Campus is located within half an hour’s drive (well, maybe an hour with traffic) from sites where I studied Joshua trees as a graduate student, and it has good facilities and an excellent climate for growing my favorite legume, too. (I’d be remiss if I failed to mention, as well, that CSUN should be familiar to fellow fans of “Crazy Ex-Girlfriend” as the alma mater of one Joshua Felix Chan.)
To extend a metaphor I used in an essay about being a postdoc last year, I feel like I’ve finally been called up to the big leagues. I’ve already submitted my first pre-proposal for NSF research funding with CSUN affiliation, with collaborators from the Joshua Tree Genome Project, and I’m making plans to hit the ground running with that project and others when I officially arrive on campus later this summer.
I also have a lab website and Twitter feed set up, and I’m looking for graduate students to start in the fall. The deadline to apply to the CSUN Biology Master’s program is coming up fast — interested students can find out the details here and drop me a line.
Twitter is also a crucial networking tool, helping people to connect with fellow attendees who have similar interests. Users can invite Twitter connections for coffee or look out for their name tags at the conference, paving the way for an in-person introduction, says Emily Jane McTavish, an evolutionary biologist at the University of Kansas in Lawrence. “That’s made a big difference to me at meetings where I didn’t know people,” she says. Jeremy Yoder, an evolutionary geneticist at the University of Minnesota in St Paul, used Twitter to help to organize a lunch for lesbian, gay, bisexual and transgender scientists at the First Joint Congress on Evolutionary Biology in Ottawa last year. And although these connections might not lead to immediate work advantages, one never knows who might be on one’s next grant-review panel or job-search committee, says Cruz.
If you’re bringing a smartphone or a tablet to Snowbird, you should definitely go read the whole thing.◼
So I was interviewed, along with several other University of Minnesota biologists, for an article on the UMN College of Biological Sciences website about the use of online media (mainly Twitter) by scientists. You may find that article here.◼
If you’ve just arrived here on account of my contribution to the Scientific American guest blog, welcome! I hope you’ll have a look through the archives, and consider adding me to your regular online reading. Allow me to suggest a few posts that should give you an idea about what’s going on here:
In another round of neurotic revisionism, I’m taking Denim and Tweed to full Facebook. That means this blog now has a Facebook fan page, and a new widget placed prominently in the sidebar. This makes three box-of-faces widgets in the D&T sidebar, and that’s frankly too many. So I’ll be phasing out both the Blogger and NetworkedBlogs boxes in about a month from today. (You can still follow D&T through those systems, your followership just won’t be recorded in the sidebar.) Sorry! My aim is to make this the last such rejiggering for the long term.
Resistance was futile. I’ve had the “followers” widget from Google/Blogger for quite awhile now, and it’s clear it’s not seeing a tremendous amount of use. I infer that at least part of this is because it requires readers to use a login that they don’t have, or don’t use very frequently.
So I’m going to experiment with the current lingua franca of the social internet: Facebook, via Networked blogs, which I’ve seen used to good effect on several larger, more respectable science blogs I follow. Now, if you read Denim and Tweed, and if you like it, and if you want to like it in some sort of visible manner,* you can just click on the big blue button at the bottom of the new box on the right, as illustrated here.
Seriously, please click. My little thumbnail avatar looks so lonely right now.
——— * Feel free to speculate about the probability values in the Drake equation implied by that sentence.
Yuccas and yucca moths have one of the most peculiar pollination relationships known to science. The moths are the only pollinators of yuccas, carrying pollen from flower to flower in specialized mouthparts and actively tamping it into the tip of the pistil. Before she pollinates, though, each moth lays eggs in the flower—the developing yucca seeds will be the only thing her offspring eat. How does such a specialized, co-adapted interaction evolve in the first place? My coauthors and I attempted to answer this question in a paper just published in the Biological Journal of the Linnean Society, by reconstructing the ecology of yucca moths before they were yucca moths [PDF].
One of the most basic questions in evolutionary ecology is, “why are there more kinds of this kind of critter than that kind of critter?” As in, why are there more than twenty thousand species of orchids, but only one species of ginkgo? Why are there hundreds of thousands of species of beetles, but only four species of horseshoe crab? In a literature review just released online—and my first publication as lead author!—my coauthors and I assess the support for one hypothesis: that species multiply because of ecological opportunity.
Why are there so many [insert taxon here]? Photos by Bill & Mark Bell (1 & 2), fturmog (3 & 4).
The two most influential theories of adaptive radiation—by G.G. Simpson and Dolph Schluter—have suggested that it results when a species encounters ecological opportunity. Ecological opportunity might be a newly-evolved trait, or a new habitat, or the extinction of a species’ competitors or predators. For instance, a butterfly might evolve a way to overcome the chemical defenses of an abundant plant species, or a plant introduced by humans to a new habitat might find that local pathogens aren’t as deadly to it as the ones in its native range. Ecological opportunities have the effect of granting access to new resources. We have pretty good evidence that this can allow individual populations to increase in number, and even evolve greater diversity—but is that enough to spur the rapid speciation that forms adaptive radiation? Ecological opportunity ? adaptive radiation
We’re pretty sure about steps 1 and 3. We’re still trying to figure out step 2.
Readers in certain demographic groups may think this sounds like an underpants gnome problem. But it isn’t, exactly. The gnomes’ business model can’t get to from step 1 (collect underpants) to step 3 (profit) because they don’t have a step 2. Evolutionary ecologists, on the other hand, already have their step 3 in the phenomenon of adaptive radiation. Ecological opportunity looks like a good prospect for step 1 precisely because it suggests some plausible options for step 2.
When a population encounters ecological opportunity, the new habitat, new trait, or extinction of antagonists provides access to new resources, and relaxes natural selection on the population. This leads to three phenomena usually grouped together under the term ecological release
The population experiences density compensation—more individuals can live in a particular area, creating stronger competition within the population.
Because of this stronger competition within the population, or because there isn’t much competition from other species, members of the population venture into new habitats, or use new food resources.
The population becomes more diverse, either because of the relaxed selection, or because of competition-driven selection for using new habitat and new resources.
One or more of these three aspects of ecological release turn up whenever populations find new food resources, or escape predators and/or competitors. Density compensation has been widely observed in populations colonizing new habitats, especially islands; and experiments with sticklebacks and fruit flies [$a] suggest that the stronger competition resulting from density compensation can spur the population to become more diverse in its use of resources. Bacterial populations can even evolve different specialized forms—adaptive radiations in microcosm—when introduced to new food resources.
Anoles show signs of density compensation on Caribbean islands—is that the reason behind their diversification? (Pictured: Anolis oculatus.) Photo via WikiMedia Commons
But where’s the speciation?
However, the evolution of bigger, more diverse populations is not the same thing as the evolution of new species—and that’s what adaptive radiation is really all about. These changes resulting from ecological opportunity might directly promote speciation if stronger competition leads to disruptive natural selection. Similarly, the competition-driven incentive to colonize new habitats or exploit new food sources could expose some parts of the population to different forms of natural selection, eventually causing them to evolve into specialists on the new resources. Finally, even if speciation only happens when natural barriers cut off migration, maybe larger, more variable populations provide more diversity for vicariance events to divvy up.
This is all pretty speculative, though. We still don’t know how often—or how rarely—divergent natural selection contributes to making new species. One way to deal with this is to approach the question from the other direction: look backward at the history of existing species, rather than following what happens to populations immediately after ecological release.
A backward-looking approach might use statistical analyses of the evolutionary relationships between living things to identify points in time when species formed unusually fast, and try to identify the cause. Some of my coauthors from the review paper recently published an analysis of the evolutionary tree connecting all vertebrates, and found that speciation rates increased around the origins of the largest group of birds, a large portion of the lizards and snakes, and non-marsupial mammals, among others.
This is very much a starting point, but maybe by complementing similar studies with research on populations currently evolving in response to ecological opportunity, biologists can work our way closer to understanding the origins of the endless and beautiful forms of life on Earth.
References
Alfaro, M., Santini, F., Brock, C., Alamillo, H., Dornburg, A., Rabosky, D., Carnevale, G., & Harmon, L. (2009). Nine exceptional radiations plus high turnover explain species diversity in jawed vertebrates. Proc. Nat. Acad. Sci. USA, 106 (32), 13410-4 DOI: 10.1073/pnas.0811087106
Bolnick, D. (2001). Intraspecific competition favours niche width expansion in Drosophila melanogaster. Nature, 410 (6827), 463-6 DOI: 10.1038/35068555
Blumenthal, D., Mitchell, C., Pysek, P., & Jarosik, V. (2009). Synergy between pathogen release and resource availability in plant invasion. Proc. Nat. Acad. Sci. USA, 106 (19), 7899-904 DOI: 10.1073/pnas.0812607106
Grant, B., & Grant, P. (1989). Natural selection in a population of Darwin’s finches. The American Naturalist, 133 (3), 377-93 DOI: 10.1086/284924
Kassen, R. (2009). Toward a general theory of adaptive radiation: Insights from microbial experimental evolution. Annals New York Acad. Sci., 1168 (1), 3-22 DOI: 10.1111/j.1749-6632.2009.04574.x
Losos, J. (1990). Ecomorphology, performance capability, and scaling of West Indian Anolis lizards: An evolutionary analysis. Ecological Monographs, 60 (3), 369-88 DOI: 10.2307/1943062
Schluter, D. 2000. The Ecology of Adaptive Radiation. Oxford University Press. Google Books.
Simpson, G.G. 1949. Tempo and Mode in Evolution. Columbia University Press. Google Books
Svanbäck, R., & Bolnick, D. (2007). Intraspecific competition drives increased resource use diversity within a natural population. Proc. Royal Soc. B, 274 (1611), 839-44 DOI: 10.1098/rspb.2006.0198
Wheat, C., Vogel, H., Wittstock, U., Braby, M., Underwood, D., & Mitchell-Olds, T. (2007). The genetic basis of a plant insect coevolutionary key innovation. Proc. Nat. Acad. Sci. USA, 104 (51), 20427-31 DOI: 10.1073/pnas.0706229104
Yoder, J.B., Des Roches, S., Eastman, J.M., Gentry, L., Godsoe, W.K.W., Hagey, T., Jochimsen, D., Oswald, B.P., Robertson, J., Sarver, B.A.J., Schenk, J.J., Spear, S.F., & Harmon, L.J. (2010). Ecological opportunity and the origin of adaptive radiations. Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02029.x
As part of the early promotion for next year’s ScienceOnline conference, science superblogger and chronobiologist Bora Zivkovic asked me to answer a few questions over at A Blog Around the Clock, concerning me, my research, why I write here at D&T, and what a great time I had at ScienceOnline2010. I think this is my first appearance at a blog other than D&T—thanks for having me, Bora!
It’s come to my attention that the polymath blog 3quarksdaily has announced its second annual prize in science blogging, which will be judged this year by none other than Richard Dawkins. Prizes include fame, glory, and actual cash money, apparently. I’ve already self-nominated “Dethroning the Red Queen?”, but other parties who enjoy D&T are (ahem) free to nominate additional posts. Following Nerdy Christie’s lead, allow me to suggest a few other posts with which I’m well pleased:
