Fossil pollen, vegetation, no-analogue plant communities, and species niches

1. Fossil pollen, vegetation, no-analogue plant communities, and species niches Outline 1. A Pollen Primer 2. Exercise & Discussion: Species Migration 3. No-Analogue Communities 4. Niche Theory and Novel Climates Jack Williams Department of Geography Center for Climatic Research (CCR) University of Wisconsin - Madison Support (Funding & Infrastructure) Neotoma DB

2. Key Points Fossil pollen grains preserved in lakes and mires are a primary source of information about past vegetation Migration was a primary ecological response to the Quaternary ice ages, with species range shifts measuring hundreds to thousands of kilometers. These migrations were highly individualistic – no two species behaved alike. Asa result novel communities emerged, with no modern counterpart. Individualistic species dynamics and novel communities are consistent with species having unique fundamental niches and novel climates in the past. Novel future climates likely to emerge this century… will novel communities also emerge?

3. 1. Fossil pollen: a paleovegetation proxy Transport • Advantages • Quantitative measures of plant abundance • Continuous sedimentation • Precise radiocarbon ages: <100 yr precision • Many sites • Multiple proxies (charcoal, isotopes, biomarkers, etc.) Pollen Emission Lake Coring at Silver Pond, OH Deposition Sample Pollen Grains Lake • Limitations • Labor intensive • Variable taxonomic resolution (species – family) • ~Decadal resolution (1 cm3 mud ~ 10 years) • Incomplete census of vegetation Mud 1m sediment core section from Anderson Pond, TN

4. Pollen Diagram: Appleman Lake, IN (Ragweed) (Ash) (Grass) (Oak) (Hophornbeam/ Ironwood) (Spruce) (Pine) Time No-Analog Communities: Composed of extant species, in combinations not found at present Gill et al., 2010 Science

5. 2. Migration was a primary ecological response to the Quaternary ice ages3. These migrations were highly individualistic – no two species behaved alike.

6. When climates change, species have four choices • Sit tight and hang on • Migrate • Evolve • Die

7. Pollen Viewer Vegetational Responses: Range and Abundance Shifts Spruce Pollen 21,000 15,000 11,000 Modern 7,000 % % Ice Ice Ice % % No Data Williams et al. (2004) Ecological Monographs • http://www.ncdc.noaa.gov/paleo/pollen/viewer/webviewer.html • (or, Google “Pollen Viewer”) • (note: requires Java installed on your Browser)

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9. 4. Asa result novel communities emerged, with no modern counterpart.5. Individualistic species dynamics and novel communities are consistent with species having unique fundamental niches and novel climates in the past.

10. No-Analogue Communities: Species that today are mostly disjunct were closely associated in past Picea (Spruce) 15,000 13,000 1,000 Fraxinus (Ash) 21,000 15,000 13,000 1,000 Williams et al. (2004) Ecological Monographs

11. Pollen Diagram: Appleman Lake, IN (Ragweed) (Ash) (Grass) (Oak) (Hophornbeam/ Ironwood) (Spruce) (Pine) Time No-analogue communities prevail at Appleman Lake, IN between ca. 13,700 and 11,900 years ago Gill et al., 2010 Science

12. We can quantify the dissimilarity between fossil and modern pollen assemblages Squared-Chord Measure of Dissimilarity between pollen assemblages i and j dij=dissimilarity between assemblages i and j pik=relative abundance of taxon k in assemblage i

13. Example Relative abundances expressed as fractional values (between 0 and 1)

14. When is a fossil pollen sample a ‘no analogue’ sample? • It must have a high dissimilarity to all modern pollen samples • Requires setting a ‘no-analogue’ threshold of dissimilarity North American Pollen Database (Whitmore et al. 2005)

15. We can map the minimum dissimarity as an indicator of no-analogue communities Minimum Dissimilarity from Present (pollen)

16. Niche Theory: Four Fundamental Concepts 1. Fundamental Species Niche: the set of all environments in which a species can grow and reproduce 2. Realized Environmental Space: The set of environments existing at a moment in time. 3. Potential Niche: The set of environments available to a species at a moment in time (i.e. the intersection of fundamental niche and realized environmental space) 4. Realized Niche: The set of environments occupied by a species Realized Environmental Space Climate Variable 2 Fundamental Niche Potential Niche Realized Niche Climate Variable 1 redrawn from Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220

17. Niche theory predicts that no-analog communities can form in response to novel environments • Species’ fundamental niches may extend and overlap outside the current realized climate space • Past climates may differ substantially from modern climates. • Novel climates: climatic conditions that do not exist today. • No-analogue associations of species may form under climates unlike any at present. Climate today Past climate Novel climate Climate Variable 2 Species 1 Species 2 No-analogue species association Climate Variable 1 redrawn from Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220

18. We can use the contemporary range of species to estimate their climatic niche (White spruce) January Temperature January Precipitation (mm) Thompson et al. 1999

19. Web Resources – Niche Visualizations 1) Atlas of Relations Between Climatic Parameters and Distributions of Important Trees and Shrubs in North America • http://pubs.usgs.gov/pp/p1650-b/ • GOOGLE: Thompson tree atlas 2) North American Modern Pollen Atlas • http://www.ncdc.noaa.gov/paleo/pubs/williams2006/williams2006.html • GOOGLE: modern pollen atlas Extra credit exercise on handout: Map your own niche!

20. The no-analog communities are linked to highly seasonal insolation and temperature, wet conditions, and the decline of North American megafauna North American Climates: Modern vs. 14,000 yr BP Evidence for high temperature seasonality Modern Geographic and Climatic Range of Fraxinus (Ash) Less seasonal More seasonal Jackson and Williams 2004 AREPS Kutzbach et al. 1998 QSR Fraxinus present Fraxinus absent Thompson et al. 1999, USGS Atlas

21. 6. Novel future climates likely to emerge this century… will novel communities also emerge?

22. No-Analogue Climates: Past, Present, Future 2050 (°C) Modern 15 ka Climate simulations from CCSM climate model (Liu et al. 2009) (°C) Veloz et al. unpub.

23. Novel Climates Most Common in Tropics Projected Distributions of Novel Climates by 2100AD • Novel climates projected to emerge in tropics and subtropics • Logical outcome of warming world • Combined with many other anthropogenic drivers • Land use, invasive species, nutrient cycling… • We should expect the unexpected A2 (CO2atm=850ppm by 2100AD) Climatic Dissimilarity Low High B1 (CO2atm=540ppm by 2100AD) Williams et al. (2007) PNAS

24. The closest future climatic analogs don’t always come from modern climate! Climate simulations from CCSM climate model (Liu et al. 2009) Veloz et al. unpub.

26. Sporormiella, a ‘megafauna proxy’ Jacquelyn Gill • Sporormiella, a dung fungus found in many species, including mammoths (van Geel et al. 2008) • Spores found in high abundances (>2%) in Pleistocene sediments (Davis & Shafer 2006) • A proxy for mammalian dung loadings and mammalian herbivore biomass • Also preserved in lakes & mires  allows precise sequencing of vegetation change and megafaunal decline Burney et al. 2003 PNAS

27. Pollen Diagram: Appleman Lake, IN (Ragweed) (Ash) (Grass) (Oak) (Hophornbeam/ Ironwood) (Spruce) (Pine) Time No-Analog Communities: Composed of extant species, in combinations not found at present Gill et al., 2010 Science

28. Time Other sites confirm linkage between Sporormiella decline, no-analog plant communities, and fire regime shift Red=charcoal (inverted scale) Black=Minimum SCD Blue=Sporormiella Gill et al., in press, Science

29. EXTRA CREDIT EXERCISE: Visualizing Niches

30. The Quaternary is an excellent model system for studying biotic responses to climate change Ocean Sediments Ice Cores 2. Data-rich – in both climatic and ecological data Loess 1. Frequent, large, and rapid climate variations LAKES Tree Rings Speleothems Greenland Temperature IPCC 2007 WG1 Ch6 Fig. 6.3 Age (103 years before 2005)

31. C:\Jack\Figures\OthersFIgs\GISPtempLGM-0.JPG The Last 20,000 yrs • Global temperature: rose ~5°C • Ice sheets melted • Sea level: rose by 120m • CO2atm: rose from 190 to 280 ppm Temperature Variations Since the Last Glacial Maximum GISP2 Ice Core (Greenland) Bølling-Allerød Difference from present (°C) PLEISTOCENE || HOLOCENE Age (years before present [BP]) Time (Grootes et al. 1993 Nature)

32. Dramatic Biotic Responses Spruce Pollen Distributions: 21000 years ago to present Spruce Pollen 21,000 15,000 11,000 Modern 7,000 % % Ice Ice Ice % % No Data Williams et al. (2004) Ecological Monographs • Species ranges shift 102-103km • Humans enter the Americas • 34 genera of vertebrates go extinct • Species reshuffle, new communities emerge http://www.jqjacobs.net/anthro/paleoamericans.html Google: Pollen Viewer

33. Pollen Diagram: Appleman Lake, IN (Ragweed) (Ash) (Grass) (Oak) (Hophornbeam/ Ironwood) (Spruce) (Pine) Time No-Analog Communities: Composed of extant species, in combinations not found at present Gill et al., in press, Science

34. Species that today are mostly disjunct were closely associated in past 15,000 years ago 1,000 years ago Picea (Spruce) Fraxinus (Ash) Percent Pollen No Data Williams et al. (2004) Ecological Monographs

35. No-analog communities most common between 17,000 and 12,000 years BP Minimum Dissimilarity from Present (pollen) Modern Pollen Samples Squared-Chord Measure of dissimilarity between pollen assemblages i and j pik=relative abundance of taxon k in assemblage i

36. The No-Analog Problem: How do we study ecosystems we’ve never seen? • Why were past communities unlike any today? • Will novel communities develop in response to 21st-century climate change? 2. Are the no-analog communities and the megafaunal extinction linked? • What are the ecological consequences of the current wave of extinctions?

37. Thesis: The late-glacial no-analog plant communities caused by novel climates and altered disturbance regimes. Climate Humans Vegetation Fire Mammals Key Drivers: Climate 1. High temperature seasonality 2.High precipitation Humans(?) 3. Megafaunal extinction and enhanced fire regime

38. Niche Theory: no-analog communities arise in response to novel environments Present climate domain “Climate Space” Past climate domain ‘No-analog’ or ‘novel’ climate Climate Variable 2 Species fundamental niche Species 2 No-analog species association Species 1 Climate Variable 1 Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220 Williams and Jackson (2007) Frontiers in Ecology and Evolution

39. The no-analog communities are linked to higher-than-present temperature seasonality • Evidence: • Global Climate Models: late-glacial climates were more seasonal than present • Apparent truncation of potential species niches by the seasonal edge of the modern climate envelope North American Climates: Modern vs. 14,000 yr BP Modern Geographic and Climatic Range of Fraxinus (Ash) Less seasonal More seasonal Jackson and Williams 2004 AREPS Kutzbach et al. 1998 QSR Fraxinus present Fraxinus absent Thompson et al. 1999, USGS Atlas

40. Last 21,000 years: Temperature seasonality correlates well to no-analog communities No-Analog Communities (Min. SCD) Temperature Seasonality Time Williams and Jackson 2007

41. Implication: species distributional models that are based on observed species-climate relationships should perform poorly for novel climates… surprises are likely Present climate domain “Climate Space” Past climate domain Species realized niche Climate Variable 2 Species fundamental niche Species 1 Climate Variable 1 Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220 Williams and Jackson (2007) Frontiers in Ecology and Evolution

42. But wait: what about that megafaunal extinction? Pleistocene megafauna No-Analog Communities (Min. SCD) Temperature Seasonality Time Williams and Jackson 2007 • Problem: The temporal sequence of vegetation change and megafaunal extinction is imprecisely known. • Pollen collected from lakes & mires • Bones collected from caves, digs, etc. • Hypotheses: • No relationship • Habitat loss megafaunal extinction • Megafaunal extinction  altered herbivory  vegetation change http://www.jqjacobs.net/anthro/paleoamericans.html

43. Appleman Lake: the Sporormiella decline precedes the no-analog communities (Ragweed) (Ash) (Grass) (Oak) (Hophornbeam/ Ironwood) (Spruce) (Pine) Time • Sporormiella decline: 14.8 to 13.7 kyr • First charcoal peak: 14.1 kyr Gill et al., in press, Science

44. Implications for the Future Projected Distributions of Novel Climates by 2100AD • Novel climates projected to emerge in tropics and subtropics • Logical outcome of warming world • Combined with many other anthropogenic drivers • Land use, invasive species, nutrient cycling… • Expect the unexpected – ecological surprises may be the new normal. A2 (CO2atm=850ppm by 2100AD) B1 (CO2atm=540ppm by 2100AD) Williams et al. (2007) PNAS

45. Summary • Both global-change ecologists and paleoecologists face the ‘no-analog’ problem • No-analog communities linked in past to: • Novel climates (higher-than-present temperature seasonality, high precipitation) • Megafaunal extinction and altered disturbance regime • Novel climate states pose a major challenge for observationally based species distribution models • We are pushing the climate system to a geologically novel state: we should expect surprises.

46. Some of these surprises may be faster than we think “Beetles are the bullet that killed the pines, but drought pulled the trigger”

47. Species Responses to Quaternary Climate Change Patterns Species migrate. Ranges are highly dynamic. This migration is individualistic – i.e. communities do not move as intact units. Implications: Co-evolutionary relationships among many species must be fairly weak. Species must be able to survive some range of climate variability.

48. 1) Species ranges are highly dynamic Vegetational Responses: Range and Abundance Shifts Spruce Pollen 21,000 15,000 11,000 Modern 7,000 % % Ice Ice Ice % % No Data Williams et al. (2004) Ecological Monographs Google: Pollen Viewer

49. Setting the Stage: Climate Variations and Quaternary Ice Ages Species Migration No-Analog Communities and Climates Genetic Legacies Extinction OUTLINE

50. Plant taxa that rarely co-occur today… (Spruce) (Ash) Thompson et al. (1999a,b) Atlas of Woody Plant Distributions…