Understanding the diversity of life is central to the mission of the Natural History Museum. Science sees diversity in many ways: populations, species, ecosystems, individuals or genes and the Museum's collections of more than 70 million items are used by scientists for research on many aspects of diversity. The collections have developed over the past 250 years with a very strong emphasis on the idea of the species, but reflect diversity within species as well - the differences between populations from different areas, for example.
What separates one species from another is not always an easy question: it is a key question for the science of taxonomy and has important practical implications. The established biological species concept defines two species as two groups of organisms that cannot interbreed to produce fertile young when in the same location. When different species are present in the same location, this can be observed in theory. However, when two groups of similar organisms are geographically separate, are they different populations, different subspecies, or different species? This will be the case for many thousands of species and has led to heated debate among scientists who have taken different views.
Beyond science, this is of importance because the species is often used in practical policy-making and economic activity. There needs to be accurate definition for biodiversity conservation, pest control in agriculture, human health and other activities.
A group of collaborating scientists from Oxford and Cambridge Universities and from BirdLife International have used the Museum's bird collections to try to define a reliable standard for species. They aimed to define how much genetic, morphological and behavioural distance there was between known species and subspecies, and within species.
The scientists looked at pairs of 58 closely-related species and subspecies, including European swallows and linnets, North American blackbirds and tyrant flycatchers and African Illadopsis. They examined more than 2,000 specimens from the NHM bird collections and more than 140 from Louisana State University for morphological data and plumage, and looked also at song, ecological and behavioural differences. The intention was to use this suite of characters to define a reliable and objective difference between species.
Tobias et. al (2010) published their results in the journal Ibis, concluding that this is a reliable way of confirming species separations and propose that this could be used increasingly to improve the reliability of understanding of bird diversity. An article in Nature (Brooks and Helgen, 2010), commenting on the paper, suggested that there could be very interesting possibilities in applying similar techniques to other groups of organisms and with DNA data.
Thousands of visiting scientists routinely use the Museum's collections as a research resource: the collection represents a body of evidence to address new questions and test established knowledge of natural diversity, and continues to develop as research interests expand.
TOBIAS, J. A., SEDDON, N., SPOTTISWOODE, C. N., PILGRIM, J. D., FISHPOOL, L. D. C. and COLLAR, N. J. (2010), Quantitative criteria for species delimitation. Ibis, 152: 724–746. doi: 10.1111/j.1474-919X.2010.01051.x
Brooks, T. M. and K. M. Helgen (2010). "Biodiversity: A standard for species." Nature 467(7315): 540-541.