Instructor Notes

Pre-discussion Introduction

  • Instructor notes: Most students have little to no knowledge of the large changes in environment that have occurred even fairly recently. The goal of this unit is to expose students to the idea that dynamics are natural and that the past can be useful for understanding the future. Because of the limited exposure students have to dynamics - and especially paleoecology - a brief introduction explaining why they are reading about this can be useful for setting the stage for the discussion. Below is an example introduction to the unit. As humans, our view of nature is dominated by what we experience and our memory is short. We have a tendency to assume that the world around us reflects the way it has always been, the way it ‘should’ be. As ecologists, most of us will obtain advanced degrees and never be exposed to how the earth has changed over its history. When we are exposed to earth’s history, it’s in the context of a world dominated by extinct lineages or extremely distant relatives of modern species. It can seem like earth’s past has little relevance for today because of course everything was different when dinosaurs roamed the earth. I wanted to start off the ecological dynamics section by exposing you to some of the major changes that have occurred relatively recently, so we can broaden our perception of nature and the role of change. I chose the Pleistocene because the end of that age was not actually all that long ago, especially from an evolutionary perspective for the species still alive today

Discussion Questions:

Hofreiter & Stewart “ecological change, range fluctuations, and population dynamics during the Pleistocene”

Describe the Pleistocene?

  • geological time period that ended ~ 10k years ago
  • Marked by big climate fluctuations
  • example, during times of changes from stadials to inter- stadials the average temperature changed by 5–10 C within as little as a few decades (From ‘Hofreiter and Stewart - 2009 - Ecological Change, Range Fluctuations and Populati_AKF4T6WR.pdf’, page 1)
  • geography was different - water bound in glaciers dropped sea level, connecting islands to mainlands and drying out the North Sea
  • Species were found in very different locations
  • range shifts common
  • End of Pleistocene, loss of large land vertebrates

How is the Pleistocene similar but different to today?

  • Similarities:
    • rapid climate change
    • Shifting species
    • Human effects on large fauna
    • Same species (except for those that went extinct)
  • Differences:
    • Higher land and resource appropriation by humans today
    • Novel habitats (cities)
    • Increased fragmentation via roads, farmlands, and other human-built barriers to movements
    • Increased movement between continents via introduced species

Williams and Jackson Now that we have a general feel for the Pleistocene, let’s think about what it can tell us about ecological change.

What is a no-analog community and why did they show up in the Pleistocene?

  • community composition never seen before
  • seem related to novel climates
    • higher seasonality

Are the issues that created non-analog communities in the past likely to be issues in the future? Why?

  • we only see part of the fundamental niche
  • Novel climates can reveal parts of the fundamental niche not seen before
  • That can lead to species exhibiting responses that we did not anticipate

Are there different challenges for predicting species responses to regionally or globally novel climates?

  • Global: we have no way to predict how species will respond to a climate envelope that we have no data for
  • Regional: even if the climate occurs somewhere in the world, for the local species this is novel. Unless this regionally novel climate is within dispersal/ migration distance of the historical climate location. Local species responses will be unknown

What do changes in the past tell us about what to expect in the future?

  • Novel communities
  • Unexpected changes in species preferences

What does the past tell us about the challenges we may face with forecasting?

  • Expect the unexpected
  • Across all systems and taxa
  • Change is coming
  • We are missing important data to make species predictions?
  • While species may respond unexpectedly, it is not guaranteed that those responses will be negative ones. Some species may do worse but others better than expected due to hidden parts of their niches.