Chapter 2 Biodiversity and Extinction

Discussion Questions

1. Compare the biological, morphological, and phylogenetic species concepts. Give examples of situations in which each of these concepts would be inappropriate. Finally, describe the unifying theme that underlies all three of these approaches to defining species.
2. Explain one strategy that has been used to estimate the total number of species, or amount of species diversity, on Earth. Describe the relative strengths and weaknesses of this approach.
3. Do you think that the mismatch between the predicted and observed numbers of extinctions undermines the credibility of conservationists? Why or why not?
4. Explain the logic of using a species-area approach to estimate extinction rates. Now, critique the approach. What are its major shortcomings?
5. The species-area relationship (SAR) has been used by many researchers to generate predictions about the global rate of extinction. Describe one way in which the SAR approach is conservative (meaning that it will tend to underestimate the true rate of extinction).
6. Recently, He and Hubbell pointed out a major problem with the SAR approach that causes it to overestimate extinction rates. Briefly explain the problem they detected.
7. If it would cost $50 million to save a tiny fish called the snail darter (Percina tanasi) that lives in rivers in the southeastern United States, how would you justify spending the money to an angry taxpayer who did not want public money spent on such a "silly little fish"?

Group Projects

• Use the IUCN Red List of Threatened Species to compare patterns of endangerment and threat for three nations of your choosing. For each nation, record the total number of critically endangered (CR), endangered (EN), and vulnerable (VU) species. Next, record the number of CR, EN, and VU species affected by each of the major categories of threat (such as habitat loss, invasive/alien species, harvesting). Use these data to write a report comparing the patterns of endangerment and threat. Think carefully before drawing conclusions; for example, could the differences you observe be due to differences in the total number of species that inhabit each nation or to differences among nations in the funding made available to study these issues?
  
  
• Use the Tree of Life website to explore the hierarchical taxonomy of living organisms. Starting at the root of the tree of life, select branches of the tree to navigate to the following three organisms: Philothalpus antennaria (a rove beetle in the family Staphylinidae), Homo sapiens (humans), and Salticus palpalis (a jumping spider of the Salticinae family). Record the choices that correctly lead you from the root of the tree to each target organism. For example, if the target organism were a crab, then you would record Eukaryotes, Animals (metazoa), Bilateria, Arthropoda, Crustacea, Malacostraca, Decapoda, and so on. The point of this exercise is to help you become aware of the enormous diversity of both living and extinct species and to familiarize yourself with the way scientists organize species into hierarchical groupings. Write a few paragraphs reflecting on what you found to be the most surprising aspect of each navigation exercise. Also, briefly describe and compare the diversity of groups that you see as you navigate through the web of life to each of the three target species.

Useful Websites

• NatureServe Explorer provides conservation assessments for the plants, animals, and ecosystems of the United States and Canada. NatureServe lists information such as scientific and common names, conservation status and needs, distribution maps, life histories, and more for over 70,000 plants, animals, and ecosystems and provides in-depth coverage for rare and imperiled species. http://explorer.natureserve.org


• Tree of Life web project provides over 4000 individual webpages, each dedicated to a particular group of organisms. The site is structured hierarchically to resemble a complete cladogram of evolutionary history from single-celled prokaryotes to contemporary, complex, multi-cellular organisms. http://www.tolweb.org


• The What is Missing? Foundation seeks to connect people to the reality of the ongoing extinction crisis through multimedia displays that merge science and art. In addition to scores of short videos, the foundation's website provides an interactive map on which each dot represents a species or ecosystem that has been lost or is currently under grave threat. The map highlights actions being taken today to prevent further loss. Whatismissing.net


• WildFinder is a database of species' geographic ranges and visualization tool, searchable by taxonomic group or ecoregion. This website is curated by the World Wildlife Fund. www.worldwildlife.org/wildfinder

Suggested Readings for In-class Discussion

• Boitani L, Mace GM, Rondinini C (2014) Challenging the scientific foundations for an IUCN Red List of Ecosystems. Conserv Lett. http://onlinelibrary.wiley.com/doi/10.1111/conl.12111/full (open access)
  
  
• Costello MJ, May RM, Stork NE (2013) Can we name Earth's species before they go extinct? Science 339: 413-416.
  
  
• Dornelas M, Gotelli NJ, McGill B, Shimadzu H, Moyes F, et al. (2014) Assemblage time series reveal biodiversity change but not systematic loss. Science 344: 296-299.
  
  
• Dirzo R, Young HS, Galetti M, Ceballos G, Isaac NJ, Collen B (2014) Defaunation in the Anthropocene. Science 345: 401-406.
  
  
• He F, Hubbell SP (2011) Species–area relationships always overestimate extinction rates from habitat loss. Nature 473: 368-371.
  
  
• Vellend M, Baeten L, Myers-Smith IH, Elmendorf SC, Beauséjour R, et al. (2013) Global meta-analysis reveals no net change in local-scale plant biodiversity over time. PNAS 110: 19456-19459. http://www.pnas.org/content/110/48/19456.short (open access)