1. Pleistocene and Holocene Epochs (Ice Age) Period of marked change in species despite short duration Recent event  relates to current species Traceable change through tree rings, animal and human middens, pollen, marine indicator species Also important because event did not obliterate record of past events

2. Glaciation

3. Minor glaciation Glaciation

4. Causes of Glaciation Earlier glaciations caused by contiental drift Continents 2 mya near/in current positions Once thought Pleistocene glaciation caused by changes in solar output Relatively stable solar output for last 590 million years (Gates 1993) Been linked to Milankovich cycles + albedo

5. Obliquity Eccentricity Periodicity of 100,000 yr Periodicity of 41,000 yr Periodicity of 22,000 yr Precession

8. Extent of Glaciation Most of Pleistocene and Holocene were glacial with short inter-glacial periods Wisconsin Illinoian Kansan Nebraskan

9. Extent of Glaciation 80% of glacial ice in Northern Hemisphere –North America, Europe, Atlas Mtn. (NW Africa) Southern Hemisphere –Chile and Argentina –Australia – limited to Victorian Alps, Central Plateau of Tasmania –New Zealand Alps

13. Climatic Effects Sheer Size of glaciers – area covered and height (2 – 3 km) changed wind and current patterns Lake levels rose in SW US

14. Climatic Effects Less fluctuation in temperature near glaciers

15. Climatic Effects Temperatures lower away from equator. Tropic drier How did tropical species maintain and even increase diversity?

16. Sea Level Fluctuations Rapid glacial and interglacial fluctuations Sea level dropped 100 – 160 m during glacial periods Created land bridges

20. Retreat of Wisconsin glacier caused rapid rise in sea level (plus compression of crust, causing sea water to enter part of Great Lakes

21. Result – some Atlantic species found in Great Lakes, including several species of coastal plants Range of seaside spurge (Ammophlia brevigulata) – note disjunct range

22. SHEER MASS - Weight of glaciers compressed crust!!

23. Biogeographic Responses to Glaciation Biogeographic dynamics of Pleistocene triggered by: Changes in location, extent, and configuration of a species prime habitat Changes in the nature of climatic and environmental zones Formation and closing of dispersal routes

24. Biota’s Response to Glaciation Species were adapted to long-term conditions of relative stable climates, reponses were: Able to “float” with their optimal habitat as it shifted Remained in in same location and adapted to new conditions Range reduction and extinction See Box 9.1

25. Biogeographic Responses to Glaciation Some vegetative and marine zones increased they areal coverage Steppes, savannahs  open-canopied ecosystems (generally drier climate) Closed-canopy ecosystems generally decreased (especially tropical rain forests Changes greatest in mid-latiturdes (35 to 55°)

28. Elevational change in Andes. Rise and compression

29. Elevational change in SW US mountains

30. Change in upper elevational limit of forests – note timing of responses

31. Drier Climate – recurring theme

34. Variation in relative abundance of vegetative communities since last glacial maximum. Note variability over time and rapid change.

35. Barriers and Corridors Changes in biota distribution not uniform latitudinally North America – many corridors –Mississippi River –Rocky and Appalachian Mountains

41. Barriers and Corridors Changes in biota distribution not uniform latitudinally Eurasia – corridors –Ural, Carpathian, and Atlay mountains –Rocky and Appalachian mountains Eurasia – barriers –Mediterranean Sea –Caucasus, Alps, and Pyrenees mountains

43. Corridors and Dispersal Lowering of elevation of montane vegetative zones as mechanisms of dispersal – cross to other mountains and mesic lowlands Oceanic zonal patterns also changed (Fig. 9.12) even though open ocean temperature change smaller (2 – 3°C) Stenothermal species had potential to move to opposite poles (Fig. 9.25)

44. Aquatic Ecosystems Glaciers are major lake builders Seen as aftermath of glaciation Kettle lakes, moraine lakes, paternoster…. Glacial lakes –Meltwater retained by ice dams –When dams break  large mass freshwater into shallow seas, carve out river valleys

45. Lake Agassiz Released 163,000 km 3 in Tyrrel Sea (Hudson Bay), Atlantic Ocean Also down Glacial River Warren (now Minnesota and Mississippi Rivers)

47. “Wet Aridlands” – Pluvial Lakes Formed in what are now deserts Large freshwater or saline lakes Caused by low evaporation + high precipitation Typically formed in broad basins between mountain ranges Lake Bonneville – remnants are saline lakes (Great Salt Lake)

49. Refugia “Safe” zones or habitats, offered areas where ice did not cover, even in the area of the ice sheet Haffer’s Pleistocene refugium hypothesis –Fragmentation of Amazonian rainforest by precipitation levels –Lead to isolation and divergence of species and subspecies New model – inundation of basin by 100 m rise in sea level and Amazon islands

50. Emphasis is on distribution of subspecies and number of endemic species

51. Nunatuks

54. Refugia and Endemics

55. Glaciation and Extinctions Plants – most extinctions at the onset of glacial events Species persistence by –Disperse with climatic zones –Refugia and dispersal –Adaptation to new conditions

56. Glaciation and Extinctions Marine Invertebrates – also most extinctions at the onset of glacial events Causes –Stenothermal species –Limited ability to disperse (non-planktonic larvae)

57. Glaciation and Extinctions Terrestrial vertebrates – pattern less clear Overkill hypothesis – impact of humans as they expanded their range. Would lead to loss of large herbivores as well as their associated predators and scavengers Size-Space Climate – many of extinctions of all sized- terrestrial vertebrates was low and constant until the late Wisconsin

60. Australia: Black – extinct during Pleistocene/early Holocene Shaded – extinct or endangered after European colonization White – Extant, non-endangered species