Peter Wilf's research

This is a synopsis of Peter Wilf's research program. It is all text, but please see my publications page for downloadable research articles, my news and commentary page for links to generally well-illustrated reporting about my work, and Rebecca Horwitt's Paleo-illustrations for superb reconstructions of ancient life I am studying with my colleagues.

Fossil leaves are extremely sensitive indicators of past climates, plant-insect interactions, biodiversity, and the effects of major environmental disturbances. These data provide deep-time analogs that uniquely illuminate modern ecosystems and their possible responses to anthropogenic change. The time period I study is the latest Cretaceous through middle Eocene, 67-45 million years ago (m.y.), an interval characterized by global disturbances that are closely spaced in geologic time. These include latest Cretaceous warming and cooling (67-65 m.y.), the end-Cretaceous mass extinction (65 m.y.) and ensuing recovery during the Paleocene (65-55 m.y.), and both abrupt and long-term warming across the Paleocene-Eocene boundary (55 m.y.). I enjoy collaborations with numerous colleagues and students and extensive field work, especially in the Western Interior USA and Patagonia, Argentina.

Three areas of my research are highlighted below. Some other areas include new uses of leaf physiognomy to quantify paleoclimates and paleoecological variables, angiosperm leaf architecture, and my participation in the Australian Research Council-New Zealand Research Network for Vegetation Function, directed by Dr. Mark Westoby, Macquarie University.


End-Cretaceous (K-T) mass extinction and Eocene global warming
   
The K-T extinction (65 m.y., best known as the “dinosaur extinction”), eliminated about 70% of species on Earth. All life on our planet today traces to the survivors of this last great catastrophe. Most researchers agree that an extraterrestrial impact caused the K-T extinction, but a detailed understanding requires quantitative analyses of turnover and a finely-resolved climate record. With Drs. Kirk Johnson (Denver Museum of Nature & Science), Conrad Labandeira (Smithsonian National Museum of Natural History) and others I am studying terrestrial climatic and vegetational changes using the most extensive (more than 22,000 specimens) and complete plant fossil record for this interval, from southwestern North Dakota. So far we have found the first evidence of a mass extinction of insects, discovered a fine correlation between marine and terrestrial temperature records, and quantified the plant extinction in detail.

The early Eocene (55-49 m.y.) featured an extended global warming interval including the highest temperatures of the last 70 million years. My doctoral work in southwestern Wyoming produced a detailed paleoclimatic and paleobotanical record, showing a marked (~7°C) temperature increase and accompanying rise in plant diversity. Warm winter temperatures in continental interiors at middle latitudes do not exist today and present a persistent ground-truthing problem for computerized modeling programs used to predict future climates. I found that the warm temperatures did not correlate with, and thus were not caused by, the presence of large Eocene lakes in Wyoming as suggested in some climate modeling studies. This result and others like it from paleontology have helped stimulate improvements in climate models.

Origins of South American plant diversity

South American floras are the most diverse on Earth, but little is known about when diversification occurred. I am the principal investigator, along with four co-principal investigators and several collaborating investigators and students in the U.S. and Argentina, of a major study of Paleocene and Eocene floras from Patagonia, Argentina. Patagonia has a rich but historically undersampled record from the globally warm Paleogene. The current phase of this work is funded through 2008 by the NSF Biodiversity Surveys and Inventories Program. So far we have run three major expeditions to Patagonia (1999, 2002, 2005), which have generated many new discoveries. For example, nearly 5,000 specimens and nearly 200 species from a classic site we are re-investigating, Laguna del Hunco, show that some of the world’s most diverse Eocene floras grew in Patagonia. This result is strong evidence for an ancient history of high diversity in warm areas of South America. Affinities and biogeography of these extremely diverse floras, each containing numerous previously unknown species, are the topics of several ongoing investigations. The principal Argentine institution in this project is the Museo Egidio Feruglio in Trelew, directed by Dr. N. Rubén Cúneo.

Evolution of plant-insect associations

Terrestrial plants and insects today account for the majority of the Earth's biodiversity, and almost half of insect species are herbivores. Today's ongoing global warming and habitat loss will impact insect life cycles, distribution, and diversity. A key development in my research program was recognition of the breakthroughs in knowledge available from the abundant, diverse, and well-preserved insect-feeding damage found on fossil leaves. Dr. Conrad Labandeira and I examined the responses of insect herbivores to Paleocene-Eocene warming, at a time when body fossils of insects are lacking, and we discovered a marked increase in insect feeding that matched predictions based on modern observations. Subsequent work on the K-T fossil leaves from North Dakota provided the first evidence for a mass extinction of insects at the K-T as well as evidence for the Late Cretaceous origin of a diverse insect group (hispine beetles), all without any fossil insects. Our work on the Laguna del Hunco flora from Patagonia shows a much greater diversity of insect feeding than in contemporaneous, comparable floras from North America, revealing another important, previously unknown component of high diversity in Eocene South America. Detailed studies of Patagonian feeding associations are in progress.

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