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The biogeographic histories of Pinus monophylla and Pinus edulis.
Cole, Kenneth*,1,2, Cannella, John1,2, Coats, Larry1,2, Arundel, Samantha2, Mead, Jim2, Fisher, Jessa1,2, 1 USGS FRESC Colorado Plateau Field Station, Flagstaff, AZ2 Northern Arizona University, Flagstaff, AZ
ABSTRACT- The last 50,000 years of biogeographic history of the pinyon pines are well documented by the abundant needles and seeds found in fossil packrat middens throughout the western United States. Pinus monophylla (single-needle pinyon) and P. edulis (pinyon pine) are especially well known due to their present and past abundance in areas well represented by this fossil record. The oldest records, from the middle Wisconsinan Period (> 30,000 yr B.P.) record P. monophylla with a surprisingly broad distribution ranging from Kings Canyon in the western Sierra Nevada across the Mojave and northern Sonoran Deserts to recently discovered records in the canyonlands of eastern Utah. These records suggest cold but dry climates. During the late Wisconsinan (30,000 to 11,000 yr B.P.) P. monophylla was still present at Kings Canyon and across the Mojave and Sonoran Deserts but the canyonlands records appear considerably wetter. After 11,000 years ago it migrated northward into the Great Basin arriving near its current northeastern limit in the eastern Great Basin as early as 7000 yr B.P. It migrated much more slowly in the western Great Basin possibly not approaching its northwestern limit until the last 2000 years. In contrast, P. edulis is not recorded in the fossil record until the late Wisconsinan when it is found in fossil middens along the Mogollon Rim and southern Colorado Plateau and eastward to west Texas. As the climate warmed after 11,000 yr B.P., it moved northward reaching the eastern Grand Canyon by 10,600 yr B.P. The midden deposits from central Utah record it arriving between 7000 and 5400 yr B.P. It evidently moved northward slowly, arriving at some northerly and easterly stands only within the last 1000 years.
KEY WORDS: Pinus edulis, Pinus monophylla, historical biogeogragraphy, migration