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.
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.
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
>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