Culturing Science – biology as relevant to us earthly beings

Archive for March 2011

The danger of appealing stories: anecdata, expectations, and skepticism

Image: DFID/Russell Watkins

This lovely image was taken by Russell Watkins in Sindh, Pakistan, and I was directed to it by a brief article in New Scientist. Reporter Seil Collins:

Covered in spiders’ webs, these cocooned trees in Sindh, Pakistan, are an unexpected result of floods that hit the region in 2010.

To escape from the rising waters, millions of spiders crawled up into trees. The scale of the flooding and the slow rate at which the waters receded, have left many trees completely enveloped in spiders’ webs.

Although slowly killing the trees, the phenomenon is seemingly helping the local population. People in Sindh have reported fewer mosquitos than they would have expected given the amount of stagnant water in the area. It is thought the mosquitoes are getting caught in the spiders’ webs, reducing their numbers and the associated risk of malaria.

I love this idea. My friends have been passing it around google reader, and it seems to make a lot of sense: More spiders, more webs, more dead mosquitoes in webs, fewer mosquitoes, less malaria. Bing bam boom.

The problem with it: It’s entirely based on anecdata. Anecdata has been my favorite word for about six months now, as well as a topic of fixation for me. It describes information from compiled from a number of agreeing anecdotes, stories, or items of hearsay — “psuedo-data [sic] produced from anecdotes” in the words of urban dictionary. Hearing that multiple people have made similar observations or had similar experiences can clue you into a trend, but hearing a lot of stories doesn’t prove anything. Storytelling is subjective and malleable, not the qualities of good data.

I haven’t been able to find a single scientific source for this mosquito/spider/flood story, though I’d give you a double high-five if you could find one for me.

So what’s the deal with data? We humans look around at our world, make observations, connect them, and use our rationality to draw reasonable conclusions. The story behind the photo makes sense: A number of separate correlations fit together. Who am I to say that we need SCIENTIFIC DATA, free from bias, to speak any kind of truth? After all, the chance to collect baseline data about mosquito and spider populations, average web coverage, mosquitoes per inch of web, etc. has passed and now we can only look back and try to remember what it was like before.

The problem with memory: It changes based on new information. And the problem with stories: They are borne from preconceived expectations.

I recently spoke with Timothy Mousseau, a biologist at the University of South Carolina, for The Scientist about the ecology of Chernobyl. If you scroll through media coverage of this topic, you’ll find many references to the Chernobyl site, which has received the highest level of radiation to date, as a wildlife preserve, one that has finally been able to thrive now that humans have left the area.

Mousseau, however, says this is a perfect example of anecdata. (Well, actually, I was the one who used the word. He thought it was very funny and I was the happiest.) Visitors go to Chernobyl expecting a wasteland, and instead they see the plants and animals that have returned in the past two decades.  These people aren’t liars — they just can’t help but exaggerate. The visitors went in with expectations about what they were going to see, and when the reality was so drastically different, they went back home and told stories about the booming wildlife, even if it hadn’t actually returned to pre-radiation standards.

But many scientists, Mousseau included, have done a great deal of ecological research at Chernobyl and have found decreases in the number and diversity of many taxa, decreased sperm counts and brain size, and physical mutations, particularly in Mousseau’s specialty species, the barn swallow. (I’m going to write up more detail on this over the weekend, do not fear!)

This story of the thriving of wildlife in the absence of humans at Chernobyl, despite the nuclear fallout, is so appealing. It’s got the perfect ingredients: It’s a bit counterintuitive, but after a moment of thought, the pieces fit. “Ohhh, people were worse for the wildlife than radiation! Thank god this nuclear disaster happened and got rid of all the people so the animals can live in peace!” And as an added bonus, it lets us feel a little better about a terrible incident. It’s really no wonder the media clung to this story — but it’s probably not true. It’s just an instance of storytelling being interpreted as data, despite its contamination with human inference and expectation.

That’s what makes me nervous about this flood/spider/mosquito story. It has very similar appeal: The bit of surprise that a flood could decrease malaria, the “ohh” moment when the patterns seem to stack up, and, once again, a bit of good-feeling about a situation that was disastrous for many people.

Oh yeah, and that the reports are totally anecdotal, made by “people in Sindh.”

I want to believe it! It’s beautiful and makes me feel good inside! But the stories that are the most appealing are probably the stories that we should be most skeptical about. And they are also the most dangerous because they are the ones that will be retold over and over.

Written by Hanner

March 25, 2011 at 12:57 pm

#nycscitweetup

There are many people in my life who think it’s strange that I like to meet up with my online friends in real life. “What if he/she is an axe murderer?” is a common remark. And it was very strange at first: The first time I met Bora I basically fled the scene because I couldn’t handle it. (Lucky for me, he stuck around for a second night so I had a chance to redeem myself.)

But it really is fun! I mean, we form these communities online of people that share very specific interests. Why wouldn’t you want to hang out with them?

I was lucky enough last weekend to get to spend an afternoon with Noam Ross (great ecology blogger, grad student, and awesome dude // @noamross) — and then last night a group of us got together at a bar in Manhattan and I had some great conversations with people I’ve known, as well as made new friends. (Awww.) I’ll shoot up a note next time we have one of these meetups in case any of y’all want to join in! We don’t bite… well, at least I don’t.

Anyway: I have the list of attendees and it is my duty to share. So here goes.

If I forgot you, i.e. you missed Krystal forcing my list into your face/beer, leave a comment and I’ll update.

Here’s to next month’s #nycscitweetup! See ya there, I hope

Written by Hanner

March 24, 2011 at 9:29 am

Natural history collections in ecological research

Once I dreamed a dream of being an evolutionary biologist.  As I imagined it, I would hang out in a natural history museum, comparing fossils to one another, taking notes on the minute differences, and piecing together the history of life. It wasn’t until a job fair years ago, when I babbled to an evolutionary biologist about morphologies, collecting specimens, and, pretty much word for word, “working in a dusty basement full of drawers of fossils,” that I realized it was an unlikely future.  The scientist looked at me like I was nuts: “Um… that’s not really what I do.  I work with DNA and genomes.”  I pushed him further, but his answer was clear: The job I described did not exist anymore.

Why can't I just hang out and compare the varying shapes of animals in a basement lair? Image: Wikimedia Commons: Haeckel, Kunstformen der Natur (1904), plate 44: Ammonitida

But while the job does not exist (or is a rare find at best), the specimens do. There are still huge archives at museums stuffed with bones, skins, ad infinitum. I am fortunate to have a friend who works at the American Museum of Natural History in New York in the mammals department. When I visited Catherine back in October, she was spending most of her time with the bat specimens, ensuring that they were in proper order and condition.

She gave me a tour of the place and I was blown away: I had always dreamed of walking into a room, stacked ceiling to floor with hippo skulls, and there I was! Catherine showed me the cleaning rooms, where fresh skeletons are picked clean by flesh-eating beetles; slid open a case in which hung tiger skins, as if it were her coat closet; and, by far my favorite, the marine mammal room, with massive whale vertebrae lined up on shelves. It’s funny to imagine a whale complaining of back pain, but there was even a pair of calcified vertebrae among the bunch.

After walking through the maze of rooms and seeing this vast collection with my own eyes, I couldn’t help but wonder: What are these even used for anymore? Certainly, education, but the museum was already packed with skeletons and stuffed animals without this backup. Catherine told me that sometimes researchers try to extract DNA from specimens, but that purpose alone doesn’t seem to make the best use of this huge collection. If taxonomy is now prescribed by genomics, are these collections, compiled and curated over centuries, going to waste?

In the past couple months, I stumbled upon three papers describing three different ways that these collections can be used to study ECOLOGY! (O, be still, my heart!)  The first, in Marine Ecology, online on Feburary 16, 2011, argues for the use of natural history collections to inform us about past species assemblages of areas that haven’t been heavily studied — baseline data. The researchers used Saba Bank, a reef in the Caribbean Netherlands, as a case study, studying coral specimens collected by divers in 1972. In this older collection, there were five species of corals collected that are no longer found in Saba Bank, suggesting that this understudied reef may need greater protection.

This may seem like an obvious use – but the authors note that it’s relatively unexploited. This may be because of poor record keeping, or the difficulty of locating collections from a specific area that have been shipped off to another museum. Another problem is that, if earlier sampling methods weren’t written down, it’s hard to know how representative a collection is of the area. Divers, not scientists, collected the Saba Bank specimens, so they may not have been trying to take note of all the species there at the time. But finding five species that survived there previously but don’t now is very useful information, no matter the completeness of the collection.

Certain organisms can provide information about their growth through growth rings, which makes their presence in natural history collections useful for learning about environmental conditions. Robert Scott is remembered for failing to reach the South Pole before Roald Amundsen – and part of the reason he was so slow is that he was so busy collecting specimens and taking measurements for SCIENCE. During his 1901 and 1913 expeditions, Scott collected Cellarinella nutti, a bryozoan that develops growth rings. Because this species was collected throughout the twentieth century, scientists were able to date the rings based on collection date, and create a timeline of relative growth: did the bryozoans grow significantly more in one decade than another?

The scientists found no change in growth between 1890 and 1970, but a sharp increase since the 1990s, as they published in Current Biology on February 22, 2011. Based on studies in related species, they think that this growth acceleration is either related to (a) greater production of phytoplankton, the food chain base or (b) a switch in the dominant species of phytoplankton, which could alternatively be more nutritious, speeding their growth. If they’re correct, it means that these museum specimens provide evidence for a recent increase in carbon storage on the seafloor in the Antarctic.

A chicken infected with avian pox with lesions around its beak and eyes. Image: Wikimedia Commons: Roman Halouzka

Natural history specimens can also be useful for tracking the development of disease in an animal population. Avian pox is caused by a DNA virus (the aptly named Avipoxvirus) that causes lesions either externally, on feather-free areas, or internally, in the mouth, windpipe and lungs. Beyond the metabolically draining effects of the virus, the pox symptoms can cause trouble feeding, cleaning and breathing. The virus is carried by mosquitoes and has been linked to the extinction of Hawaiian bird species.

Avian pox has been identified recently in the Galapagos islands, affecting mockingbird, warbler, and finch species that are only found there. To figure out when the virus arrived to help trace the progression of the infection, scientists used natural history specimens. Digging through past collections, the researchers selected birds with lesions like those found on avian pox victims, and looked for viral DNA to confirm that these lesions were caused by the virus. Their research, published on January 13, 2011 in PLoS ONE, reports the earliest specimen with avian pox they found was infected in 1898, and that the infections generally followed the pattern of human colonization. This suggests that the virus has been spread not by mosquitoes moving between islands, but by chickens and other pox-carrying fowl brought by settlers.

These perhaps unexpected uses for natural history collections — to reconstruct species assemblages, extrapolate climatic or ecological variability reflecting growth, or trace a disease through a population — should force scientists to rethink their collection methods. Historically, these collections were created to answer a simple question: What species are out there? As a December 2010 paper in the American Journal of Botany notes (hat tip to Colin Schultz), this mindset often leads to (a) oversampling of rare species, as just one or two specimens can misrepresent their abundance proportionally and (b) undersampling of common species, since just a couple specimens will do.

But gathering fully representational collections is easier said than done. These are real people out in the field, digging in the dirt or seafloor and may not have the space or energy to haul back many examples of a single species. Plus, you can go too far in the other direction; there is also no need to destroy the ecosystem for the sake of fair sampling!

But it does make clear that the age of DNA and genomics does not exclude the need for sampling. To ensure that past collections remain useful as ecological tools, scientists need to keep sampling for the sake of future science.

Edit: Fabulous commenters leave links to relevant articles! They each get a gold star sticker

  • Tracing the history of the parasite Wolbachia in butterflies using museum collections
  • Utilizing museum specimens to map deep sea creatures
  • Using bivalve fossils to study the latitudinal diversity gradient extending from the equator

This post was chosen as an Editor's Selection for ResearchBlogging.org>Barnes, D., Kuklinski, P., Jackson, J., Keel, G., Morley, S., & Winston, J. (2011). Scott’s collections help reveal accelerating marine life growth in Antarctica Current Biology, 21 (4) DOI: 10.1016/j.cub.2011.01.033

Hoeksema, B., van der Land, J., van der Meij, S., van Ofwegen, L., Reijnen, B., van Soest, R., & de Voogd, N. (2011). Unforeseen importance of historical collections as baselines to determine biotic change of coral reefs: the Saba Bank case Marine Ecology DOI: 10.1111/j.1439-0485.2011.00434.x

Parker, P., Buckles, E., Farrington, H., Petren, K., Whiteman, N., Ricklefs, R., Bollmer, J., & Jiménez-Uzcátegui, G. (2011). 110 Years of Avipoxvirus in the Galapagos Islands PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0015989

Steege, H., Haripersaud, P., Banki, O., & Schieving, F. (2010). A model of botanical collectors’ behavior in the field: Never the same species twice American Journal of Botany, 98 (1), 31-37 DOI: 10.3732/ajb.1000215

Written by Hanner

March 2, 2011 at 12:41 am