Forests communities in transition: Eocene fossil sites from western and Arctic Canada

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North Americantemperate forests in the geological past shared many plant genera with eastAsia and Europe (e.g. Pseudolarix, Acer, Sassafras, and Trochodendron).Exchange between these geographic regions is not possible today as thedispersal corridors have been too cold for 3-15 million years. Climate warmingepisodes in the geological past, however, facilitated biotic exchange betweenthem. The fossil record provides a primary record of the presence of plant taxaand of climate in the past. The proposed work will focus on the early Eoceneepoch (ca. 5647.8 MYA) when much of North America supported a tropical faunaand flora, mid-latitude mean annual temperatures (MAT) were ca. 20C with mildfrost-free winters, and even the Arctic hosted alligators. These warm highlatitude early Eocene climates opened a northern dispersal route for plants andanimals via the Arctic. Fossil localities in British Columbia present the onlyrecord of the Eocene from Canada outside the Arctic - ranging from cool (MAT1012C) elevated upland lake sites that supported forests of mixed temperateand tropical biota, to warm (MAT 1520C) lowland environments on the Pacificcoast of BC and WA that included palms. The proposed research program has theselong term objectives: (1) Develop a synthesis of changes in forest communitiesthrough time, i.e., dominance, diversity and first appearances (origination oflineages), both within and between fossil sites; (2) Determine regional andtemporal patterns of biotic diversity, and its relation to change in climate,i.e. the biotic consequences of past climate change and climate as anevolutionary driver. Short term objectives are focused on: (1) the McAbeefossil beds and targeted sites elsewhere in BC to reconstructpaleoenvironments; (2) completion of analyses of existing collections of ArcticEocene sites; and (3) systematic analysis of these sites expanding asopportunity allows to include other plant fossil sites from British Columbia tobroaden the scope both temporally and spatially to cover more of BC. Fossilsites in BC will be sampled along bedding planes to isolate forest communitiesseparated in time. These fossil sites are stratigraphically correlated usingradiometrically datable volcanic ashes, placing all of the fossil study sitesinto a chronological sequence. By documenting every identifiable fossilcollected we will reconstruct climate, forest composition, and diversity atecological time scales. The objective for detailed systematic analyses of theBC sites rich record of fossil leaves, flowers and seeds will identify keyplant families and genera and potentially clarify first appearances of thesetaxa as these Eocene sites are rich in important temperate and subtropicalplant families. This study will provide data that helps understand how forestcommunities responded to past global warming as well as on the emergence ofmodern temperate ecosystems.