Dinosaur/plant interactions: testing co-evolutionary patterns over geological timescales

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Co-evolution happens when two (or more) species interact with each other so that the evolution of one influences the evolution of the other, and vice versa (e.g., flowers and insect pollinators). Experimental studies on living organisms show that co-evolution plays a major role in promoting evolutionary radiations, but it is unclear to what extent this has been important in the history of life. On geological timescales, many plausible examples have been proposed (e.g., in mammals 'arms races' in brain size and running ability between predators and prey), but few of these have been tested quantitatively, and they remain controversial. Here, we propose to provide tests of the numerous hypotheses that have posited co-evolutionary interactions between herbivorous dinosaurs and plants during the Cretaceous Period (145-65 million years ago). These organisms provide a model system that can be viewed as a test case for assessing the importance of co-evolution over extended timescales. We will construct a comprehensive database on the global distributions of Cretaceous dinosaurs and plants, based on an exhaustive survey of the scientific literature. To these data we will add information on environmental conditions at the time (e.g., climate), and all of this will be incorporated into a Geographical Information System (GIS). The GIS is a computer-based tool that allows one to visualise and analyse spatial information. This will enable us to make detailed comparisons of the distributions in time and space of dinosaurs and plants (e.g., flowering plant families vs. specific dinosaur genera; large dinosaurs > 1, 000 kg vs. types of foliage). We will also compare the fossil records of the two groups with other variables (e.g., climate, latitude, rock type). GIS will allow these associations to be tested at an unprecedented level of detail, and it will also provide statistical tools for analysing such patterns quantitatively. This project represents a novel application of GIS techniques to testing of evolutionary questions over extended geological timescales. Using this approach we will test a variety of hypotheses of dinosaur-plant co-evolution in the following broad categories: (1) proposed correlations between the evolution of dinosaur jaw mechanisms and Cretaceous plant groups; (2) environmental controls on the distribution of dinosaur and plant taxonomic groups in time and space; (3) co-evolutionary and ecological associations between dinosaur and plant body types (highlighting, for example, comparisons between variables such as dinosaur body mass and plant morphology); (4) tight co-evolutionary interactions between specific plant and dinosaur species. The presence of specific repeated associations between dinosaur and plant groups or body types would be consistent with co-evolution; conversely, the lack of such associations would falsify co-evolutionary hypotheses. Negative results could, however, provide a clear signal of dinosaur/plant environmental preferences at a hitherto unprecedented level of accuracy. The proposed tests also address the more general issue of whether hypotheses of co-evolution are actually supported by the fossil evidence. This analysis will therefore provide the first empirical test of the extent to which herbivorous dinosaurs and plants can be said to have co-evolved during the Cretaceous Period.