Fish Tooth Microwear

Bridging the gap between ecological and evolutionary timescales: tooth wear, niche differentiation and speciation in living and fossil fishes

Understanding the ecological controls on the origin of new species is central to understanding evolution. Furthermore, this process of speciation is the "ultimate motor driving biodiversity", with significant implications for conservation biology and for evaluating how organisms respond to environmental change. But there is a fundamental problem in the study of speciation: field and laboratory experiments take place over the limited spans of human timescales, a few decades at best, yet species originate over much longer intervals of time. Our research aims to bridge this gap using a new technique. By analysing the microscopic wear patterns that form on a fishes teeth as it feeds we have been able to determine the dietary preferences and feeding ecology of fossil fishes, and test the hypothesis that speciation and evolutionary change were driven by shifts in feeding and competition for food.

Our overarching objective with this research is to bridge the fundamental gap between ecological and evolutionary timescales by testing hypotheses of ecological speciation in fossils. To do this, we further developed our method of fish tooth microwear analysis so that it can be used to determine trophic niche and dietary preferences in extant and fossil fishes. The hypothesis that underpins this research, and which we tested rigorously, is that tooth microwear in living fishes covaries with trophic niche, and that trophic niche can be determined from an analysis of tooth microwear. Our specific objectives are to test this hypothesis through a series of interlinked studies:

i) Tooth microwear in living three-spine sticklebacks – to determine the relationship between tooth microwear and trophic ecology;

ii) Tooth microwear in fossil three-spine sticklebacks – combining microwear data with ongoing morphometric studies of Miocene sticklebacks to test the hypothesis that morphological change in fossil sticklebacks was driven by niche differentiation and character displacement;

iii) Tooth microwear in living perch - to determine the relationship between tooth microwear and trophic ecology in a polymorphic species pair and test the hypothesis that tooth microwear patterns can be compared across a range of fish taxa;

iv) Exploratory analysis of tooth microwear in living bowfin - to investigate the relationship between tooth microwear and feeding in non-teleost actinopterygian, and evaluate the possibility of testing hypotheses of ecological speciation in fossil semionotid species flocks from the Mesozoic great lakes of eastern North America.

We will also continue to test and develop our methodology, including assessment of the potential impact of tooth replacement on microwear, and determination of how quickly microwear patterns characteristic of particular trophic ecologies appear.

mouthfocussmallA prey’s-eye view of a stickleback, showing the rows of small teeth lining the jaws. The skeleton has been stained to show the skeleton. Each tooth is less than a millimeter long, and roughly the thickness of a human hair. Click on image for larger version.
twotips5cmSpot the difference - scratches on two stickleback teeth. The tooth on the right is from a modern stickleback that ate food from the bottom of a fish-tank containing sand. The tooth on the left is 10 million years old, extracted from a Miocene age stickleback from the Truckee Formation of Nevada. Despite the difference in age, the pattern of scratches on the teeth is very similar, indicating that the fish had similar feeding habits. Scanning electron microscope images. Teeth are about 70 micrometers wide, roughly the thickness of a human hair. Click on image for larger version.
  • Purnell, M. A., Bell, M. A., Baines, D. C., Hart, P. J. B. & Travis, M. P.  2007.  Correlated evolution and dietary change in fossil stickleback.  Science 317. download pdf
  • Purnell, M. A., Hart, P. J. B., Baines, D. C. & Bell, M. A.  2006.  Quantitative analysis of dental microwear in threespine stickleback: a new approach to analysis of trophic ecology in aquatic vertebrates.  Journal of Animal Ecology 75, 967-977. download pdf

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