Digging up stream beds, river banks, flood plains, and road cuts and analyzing the resulting boxes of dirt and rock is time consuming and expensive. Also, many promising sites are being covered with human developments or preserved from potential erosion with large boulders or rip rap.
But are museum collections representative of what is found in nature? Maybe the curator just looked for T-rex teeth and flies in amber.
Susan Barbour Wood of Stuart, Va., a Ph.D. student in geosciences at Virginia Tech, compared the biodiversity of the mollusk collection from the Chesapeake region at the Virginia Museum of Natural History in Martinsville with bulk samples collected from five geological formations in the Chesapeake Bay area. She will report her findings at the 116th annual meeting of the Geological Society of America in Denver Nov. 7-10.
"It takes a lot of money to collect fossil-laden sediments from the field. Museum collections are already collected and sorted by the type of organism. If museum collections are representative of what is found in nature, it makes the research easier in terms of cost and time," Barbour Wood said. So I am comparing my bulk collections, time period by time period." Martinsville is near her home and the university and has extensive collections representative in terms of diversity and abundance compared to the mollusks preserved as fossils in nature from these time periods.
A bulk collection is "when you chop a cubic meter of sediment out of a river bank, for instance," Barbour Wood said. "The larger the sample, or more samples you collect, the more likely you are going to get all of the preservable organisms that lived in an area in a particular time period." For her research, she used outcrops that have already been chronologically mapped.
Barbour Wood is studying the ancestors of today's marine clams and snails. Her primary focus is the Eastover Formation of the upper most Miocene, about 6.5 million years ago. "It is an understudied period," Barbour Wood said. She is also interested in other time periods, but is collecting this one to make sure it is represented in the literature. "I want to compare the Eastover to other time periods to see how diversity of organisms changed over time, which may be in part a result of climate change."
"People who study the diversity of life are trying to database what has been on earth and why it has changed. It is hard to get grants to do this from fieldwork; therefore paleontologists may want to use museum collections. It is important to know if the curator was interested in one species or the diversity of all during the time period in question. Whether you are building a large database or doing a small study of Virginia and Maryland, you have to know how and why material was collected."
She was pleasantly surprised by her comparison of bulk diversity with the Virginia Museum of Natural History collection. "I figured it would be similar but the Museum collection's biodiversity is very much the same as field-based bulk collections from several sites."
The Virginia Museum of Natural History invertebrate fossil collections are primarily from New Jersey to Florida from the Cretaceous to Pleistocene in age. Fossils were removed from sandy to silty unconsolidated beds around river and road cuts where fresh earth is exposed and easily accessible, providing excellent coverage of time periods available on the Atlantic Coastal Plain, Barbour Wood said.
Lauck Ward, the curator, "has an extensive collection of Atlantic Seaboard organisms. He has done a good job of covering time periods and fossil localities, including some that are no longer accessible," Barbour Wood said.
Another finding is that shells in the museum collections are better preserved, she said. "It is an advantage of time. Museums can keep the best examples of specimens for collections gathered over time."
However, collections in other institutions would also have to be examined prior to use for the study of the diversity and abundance.
Museums also contain 'picked collections', which are "when you go along an outcrop and select the best examples of a particular species," Barbour Wood said. "It is not representative of what you see in nature, but picked collections are handy because they capture rare organisms that don't persist or preserve well in the environment. They are also helpful for studying a large number of a particular species, although collection of nicer, often larger, specimens can mean there are few examples of hard-to-see juveniles."
Barbour Wood concludes that museums can be an important resource to researchers because they often represent the efforts of several researchers, provide data on sites no longer available, and make data collection cost and time effective. However, it is important to understand the methodology behind the collections to control for biases and aid interpretation of data.
Barbour Wood will present the paper, "Quantifying collection biases in bulk, museum, and literature based molluscan sample data," at 8:45 a.m. Wednesday, Nov. 10, in rooms 108/110/112 of the Colorado Convention Center. Co-authors are Michal Kowalewski, professor of geosciences in the College of Science at Virginia Tech, and museum curator Lauck Ward.
Barbour Wood, who expects to graduate in December 2005, visited the museum as she was growing up and later interned there before working on her master's degree in 1998.