INFLUENCE OF LANDSCAPE STRUCTURE AND CLIMATE VARIABILITY ON A LATE HOLOCENE PLANT MIGRATION

We analyzed and radiocarbon-dated 205 fossil woodrat middens from 14 sites in central and northern Wyoming and adjacent Utah and Montana to document spa- tiotemporal patterns of Holocene invasion by Utah juniper (Juniperus osteosperma). Ho- locene migration into central and northern Wyoming and southern Montana from the south proceeded by a series of long-distance dispersal events, which were paced by climate variability and structured by the geographic distribution and connectivity of suitable habitats on the landscape. The migration of Utah juniper into the region involved multiple long- distance dispersal events, ranging from 30 to 135 km. One of the earliest established populations, on East Pryor Mountain in south central Montana, is currently the northernmost population of the species. Establishment by long-distance dispersal of that population and another in the Bighorn Basin occurred during a period of relatively dry climate between 7500 and 5400 years ago. Further expansion of these initial colonizing populations and backfilling to occupy suitable sites to the south was delayed during a wet period from 5400 to 2800 years ago. Development of dry conditions 2800 years ago led to a rapid expansion in which Utah juniper colonized sites throughout its current range. Landscape structure and climate variability play important roles in governing the pattern and pace of natural in- vasions and deserve close attention in studying and modeling plant invasions, whether exotic or natural.

[1]  K. Hibbard,et al.  BIOGEOCHEMICAL CHANGES ACCOMPANYING WOODY PLANT ENCROACHMENT IN A SUBTROPICAL SAVANNA , 2001 .

[2]  Julio L. Betancourt,et al.  APPLIED HISTORICAL ECOLOGY: USING THE PAST TO MANAGE FOR THE FUTURE , 1999 .

[3]  Saxon E. Sharpe.  Constructing Seasonal Climograph Overlap Envelopes from Holocene Packrat Midden Contents, Dinosaur National Monument, Colorado , 2002, Quaternary Research.

[4]  Kenneth L. Driese,et al.  A digital land cover map of Wyoming, USA: a tool for vegetation analysis , 1997 .

[5]  L. Tieszen,et al.  Phytolith and Carbon Isotope Evidence for Late Quaternary Vegetation and Climate Change in the Southern Black Hills, South Dakota , 1997, Quaternary Research.

[6]  E. Schupp,et al.  Lagomorphs and the dispersal of seeds into communities dominated by exotic annual weeds , 1997 .

[7]  Harold A. Mooney,et al.  Invasive species in a changing world , 2000 .

[8]  E. L. Little.  Atlas of United States trees. , 1971 .

[9]  Ophélie Ronce,et al.  Understanding plant dispersal and migration , 2001 .

[10]  S. Wells,et al.  Fire and alluvial chronology in Yellowstone National Park: Climatic and intrinsic controls on Holocene geomorphic processes , 1995 .

[11]  J. Betancourt,et al.  Patterns and sources of multidecadal oscillations in drought‐sensitive tree‐ring records from the central and southern Rocky Mountains , 2003 .

[12]  James S. Clark,et al.  Invasion by Extremes: Population Spread with Variation in Dispersal and Reproduction , 2001, The American Naturalist.

[13]  J. Overpeck,et al.  Mapped plant macrofossil and pollen records of late Quaternary vegetation change in eastern North America , 1995 .

[14]  P. Chesson,et al.  Community ecology theory as a framework for biological invasions , 2002 .

[15]  R. N. Mack.  Understanding the processes of weed invasions: the influence of environmental stochasticity. , 1995 .

[16]  N. Shigesada,et al.  Biological Invasions: Theory and Practice , 1997 .

[17]  M. B. Davis,et al.  Paleoecology of Range Limits: Beech in the Upper Peninsula of Michigan , 1989 .

[18]  James H. Brown,et al.  The paradox of invasion , 2000 .

[19]  M. Rosenzweig.  The four questions: What does the introduction of exotic species do to diversity? , 2001 .

[20]  Keith Bennett,et al.  The spread of Fagus grandifolia across eastern North America during the last 18 000 years , 1985 .

[21]  H. Mooney,et al.  Community changes following shrub invasion of grassland , 1986, Oecologia.

[22]  G. Raines,et al.  A GIS model to predict the location of fossil packrat (Neotoma) middens in central Nevada. , 2000 .

[23]  M. B. Davis,et al.  Quaternary history and the stability of forest communities , 1981 .

[24]  Charles C. Elton,et al.  The Ecology of Invasions by Animals and Plants. , 1959 .

[25]  S. Jackson,et al.  The role of Late Holocene climate variability in the expansion of yellow birch in the western Great Lakes region , 2002 .

[26]  C. Daly,et al.  A Statistical-Topographic Model for Mapping Climatological Precipitation over Mountainous Terrain , 1994 .

[27]  H. Takahara,et al.  PATCHY INVASION AND THE ORIGIN OF A HEMLOCK–HARDWOODS FOREST MOSAIC , 1998 .

[28]  Robin J. Tausch,et al.  TREE AND SHRUB DYNAMICS IN NORTHWESTERN GREAT BASIN WOODLAND AND SHRUB STEPPE DURING THE LATE-PLEISTOCENE AND HOLOCENE' , 1994 .

[29]  Robert S. Webb,et al.  Temporal and spatial patterns of Holocene dune activity on the Great Plains of North America: megadroughts and climate links , 2001 .

[30]  P. Mehringer,et al.  Postglacial history of Lost Trail Pass Bog, Bitterroot Mountains, Montana , 1977 .

[31]  Charles C. Elton.  The Ecology of Invasions by Animals and Plants , 1959, Biodiversity & Conservation.

[32]  S. Gray,et al.  Validating the use of woodrat (Neotoma) middens for documenting natural invasions , 2004 .

[33]  N. Shigesada,et al.  Invasion and the range expansion of species : effects of long-distance dispersal , 2002 .

[34]  G. MacDonald.  Fossil Pollen Analysis and the Reconstruction of Plant Invasions , 1993 .

[35]  T. Webb,.  Eastern North America , 2003, Riesling Rediscovered.

[36]  Thomas J. Stohlgren,et al.  EXOTIC PLANT SPECIES INVADE HOT SPOTS OF NATIVE PLANT DIVERSITY , 1999 .

[37]  S. Webb,et al.  Beech Range Extension and Vegetation History: Pollen Stratigraphy of Two Wisconsin Lakes. , 1987, Ecology.

[38]  J. Fa,et al.  A simple non-parametric GIS model for predicting species distribution: endemic birds in Bioko Island, West Africa , 2000, Biodiversity & Conservation.

[39]  T. Parshall.  LATE HOLOCENE STAND‐SCALE INVASION BY HEMLOCK (TSUGA CANADENSIS) AT ITS WESTERN RANGE LIMIT , 2002 .

[40]  G. Bonham-Carter.  Geographic Information Systems for Geoscientists: Modelling with GIS , 1995 .

[41]  Brooks E. Martner,et al.  Wyoming Climate Atlas , 1986 .

[42]  Richard N. Mack,et al.  Controlling the spread of plant invasions: The importance of nascent foci. , 1988 .

[43]  M. Davis,et al.  Dispersal versus climate: Expansion of Fagus and Tsuga into the Upper Great Lakes region , 1986, Vegetatio.

[44]  J. Betancourt,et al.  Holocene Vegetation and Climate History of the Northern Bighorn Basin, Southern Montana , 2002, Quaternary Research.

[45]  M Rejmánek,et al.  Plant invasions — the role of mutualisms , 2000, Biological reviews of the Cambridge Philosophical Society.

[46]  M. Schwartz,et al.  Detecting a species limit from pollen in sediments , 1991 .

[47]  D. Simberloff,et al.  BIOTIC INVASIONS: CAUSES, EPIDEMIOLOGY, GLOBAL CONSEQUENCES, AND CONTROL , 2000 .

[48]  James S. Clark,et al.  Plant migration and climate change , 1997 .

[49]  J. Stewart,et al.  Cryptic northern refugia and the origins of the modern biota , 2001 .

[50]  M. Crawley,et al.  Exotic plant invasions and the enemy release hypothesis , 2002 .

[51]  S. Levin,et al.  Mechanisms of long-distance dispersal of seeds by wind , 2002, Nature.

[52]  James S. Clark,et al.  Why Trees Migrate So Fast: Confronting Theory with Dispersal Biology and the Paleorecord , 1998, The American Naturalist.

[53]  P. Bartlein,et al.  Spatial Variations of Holocene Climatic Change in the Yellowstone Region , 1993 .

[54]  I. M. Johnstone,et al.  PLANT INVASION WINDOWS: A TIME‐BASED CLASSIFICATION OF INVASION POTENTIAL , 1986 .

[55]  D. Spittlehouse,et al.  GENETIC RESPONSES TO CLIMATE IN PINUS CONTORTA: NICHE BREADTH, CLIMATE CHANGE, AND REFORESTATION , 1999 .

[56]  D. H. Knight,et al.  Mountains and Plains: The Ecology of Wyoming Landscapes , 1996 .

[57]  G. Jacobson.  The Palaeoecology of White Pine (Pinus Strobus) in Minnesota , 1979 .

[58]  David M Richardson,et al.  Predicting Plant Migration Rates in a Changing World: The Role of Long‐Distance Dispersal , 1999, The American Naturalist.

[59]  Patricia L. Fall,et al.  Late Quaternary Vegetation and Climate of the Wind River Range, Wyoming , 1995, Quaternary Research.

[60]  W. G. Spaulding,et al.  Ploidy race distributions since the Last Glacial Maximum in the North American desert shrub, Larrea tridentata , 2002 .

[61]  S. Archer,et al.  TREES IN GRASSLANDS: BIOGEOCHEMICAL CONSEQUENCES OF WOODY PLANT EXPANSION , 2001 .

[62]  C. Barnosky.  Postglacial Vegetation and Climate in the Northwestern Great Plains of Montana , 1989, Quaternary Research.

[63]  C. Parmesan,et al.  Poleward shifts in geographical ranges of butterfly species associated with regional warming , 1999, Nature.

[64]  James Woodward,et al.  Biological invasions as global environmental change , 1996 .

[65]  R. Anderson,et al.  Fossil and genetic history of a pinyon pine (Pinus edulis) isolate , 1991 .

[66]  R. Madole.  Spatial and temporal patterns of late quaternary eolian deposition, Eastern Colorado, U.S.A. , 1995 .

[67]  W. Dean,et al.  Regional aridity in North America during the middle Holocene , 1996 .

[68]  W. Cramer,et al.  Past and future rapid environmental changes : the spatial and evolutionary responses of terrestrial biota , 1997 .

[69]  T. Swetnam,et al.  Mesoscale Disturbance and Ecological Response to Decadal Climatic Variability in the American Southwest , 1998 .

[70]  G. King,et al.  Holocene tree migration rates objectively determined from fossil pollen data , 1997 .

[71]  B. Huntley,et al.  An Atlas of Past and Present Pollen Maps for Europe , 1984 .

[72]  R. Oglesby,et al.  Paleoclimatic significance of Late Quaternary eolian deposition on the Piedmont and High Plains, Central United States , 1995 .

[73]  E. Ito,et al.  Holocene Climate in the Northern Great Plains Inferred from Sediment Stratigraphy, Stable Isotopes, Carbonate Geochemistry, Diatoms, and Pollen at Moon Lake, North Dakota , 1997, Quaternary Research.

[74]  S. Higgins,et al.  A review of models of alien plant spread. , 1996 .

[75]  C. Whitlock.  Postglacial Vegetation and Climate of Grand Teton and Southern Yellowstone National Parks , 1993 .

[76]  O. Hoegh‐Guldberg,et al.  Ecological responses to recent climate change , 2002, Nature.

[77]  J. Betancourt,et al.  A 4000-YEAR RECORD OF WOODLAND VEGETATION FROM WIND RIVER CANYON, CENTRAL WYOMING , 2002 .

[78]  A preliminary application of weights of evidence in gold exploration in Xiong-er Mountain Region, He-Nan Province , 1992 .

[79]  K. Lajtha,et al.  Plant Spatial Pattern and Nutrient Distribution in Pinyon-Juniper Woodlands Along an Elevational Gradient in Northern New Mexico , 1992, International Journal of Plant Sciences.

[80]  J. W. Beck,et al.  INTCAL98 Radiocarbon Age Calibration, 24,000–0 cal BP , 1998, Radiocarbon.

[81]  George C. Hurtt,et al.  Reid's Paradox of Rapid Plant Migration Dispersal theory and interpretation of paleoecological records , 1998 .

[82]  Paul S. Martin,et al.  Packrat Middens the Last 40, 000 Years of Biotic Change , 1991 .

[83]  D. Muhs.  Age and Paleoclimatic Significance of Holocene Sand Dunes in Northeastern Colorado , 1985 .

[84]  James T. Carlton,et al.  Biological Invasions and Cryptogenic Species , 1996 .

[85]  J. Overpeck,et al.  Responses of plant populations and communities to environmental changes of the late Quaternary , 2000, Paleobiology.

[86]  John W. Williams,et al.  DISSIMILARITY ANALYSES OF LATE-QUATERNARY VEGETATION AND CLIMATE IN EASTERN NORTH AMERICA , 2001 .

[87]  S. Juggins,et al.  Reconstruction of past changes in salinity and climate using a diatom-based transfer function , 1991, Nature.

[88]  S. T. Jackson.  Documenting Natural and Human-Caused Plant Invasions Using Paleoecological Methods , 1997 .

[89]  J. Betancourt,et al.  Late Quaternary vegetation history of Rough Canyon, south-central New Mexico, USA , 2001 .