FUNCTIONAL HYPOTHESES AND FEEDING IN FOSSILS – TOOTH MICROWEAR AND TROPHIC ECOLOGY IN EXTANT AND EXTINCT NON-MAMMALIAN VERTEBRATES

Experimental work and field ecology indicate that feeding and competition for trophic resources play key roles in driving speciation and diversification, yet these aspects of ecology are generally beyond what can be reliably determined in fossils. Obviously, this creates significant obstacles to realising the full potential of the fossil record for testing hypotheses concerning the relationship between ecology and evolution over extended timescales. Analysis of tooth microwear in two model organisms, used widely to investigate the relationship between trophic ecology, diversity and evolution, indicates that microwear provides a reliable guide to diet and feeding mechanisms. We have found that in stickleback and cichlid fishes raised under controlled experimental conditions, differences in feeding result in significant differences in microwear. The same relationship holds for wild stickleback and cichlids. Applying the method to a lineage of Miocene stickleback reveals that directional morphological change was associated with shifts in feeding and habitat, providing the first direct evidence from the fossil record for changes in trophic niche and resource exploitation coupled with microevolution. Analysis of Jurassic pycnodont fishes suggests that current hypotheses of diet and biomechanical models of feeding are oversimplified, and that the relationship between tooth morphology and trophic ecology is more complex than has been realised. We have also applied quantitative microwear methods to dinosaurs, providing robust tests of models of jaw mechanics and feeding. The power of quantitative microwear analysis for investigating diet in mammals, primates in particular, is well known; our new work on non-mammalian taxa indicates that these methods have great potential for analysis of feeding and trophic ecology - and thus adaptation, speciation, and evolution - in a broad range of vertebrates.