LATE QUATERNARY PLANTS AND ANIMALS VARY IN THEIR CLIMATIC NICHE FIDELITY (Invited Presentation)

Plants and animals will experience significant changes in climate within their geographic ranges over the next several decades. They may respond by exhibiting niche flexibility and adapting to changing climates or by exhibiting climate fidelity, shifting their geographic distributions to track their preferred climates. Identifying how species will respond to changing climate is one of the most fundamental and pressing questions in ecology and conservation biology today. Using the fossil pollen and mammal records, we reconstruct the past climatic niches of plants and animals from the late Quaternary. We then explore how well plants and animals track climate change and to what extent human impacts prevent species from tracking their preferred climates. Among the 16 most common plant taxa of North America, we find that 75% exhibit high climate fidelity over the past 18,000 years, even during times of relatively rapid climate change. Of the four taxa that do not consistently exhibit climate fidelity, three– elm (Ulmus), beech (Fagus), ash (Fraxinus)– experience a long-term shift in their realized climatic niche between the early Holocene and present day. Plant taxa that migrate longer distances better maintain consistent climatic niches across transition periods during times of the most extreme climate change. Unlike plants, the majority (67%) of mammals, have shifted their climatic niche since the Last Glacial Maximum (21 kya), mostly in the last 500 years. Interestingly many small mammals have actually expanded their climatic niches into agricultural and urban landscapes, suggesting that humans facilitate their survival. Whereas most large mammals have been extirpated from human-impacted landscapes. Different responses to climate and human impacts by different taxa and different trophic levels highlights the differential vulnerability to the dynamic changes to come. Using this understanding, we can better parameterize and prioritize connectivity strategies to conserve biodiversity on our rapidly changing planet.