1. Chapter 8 Biodiversity Reaches the Peak

2. A section of the microbial mat taken from Mushroom Springs, Yellowstone National Park. The upper green layer is primarily the cyanobacterium Synechococcus. http://carnegiedpb.stanford.edu/research/grossman2003_rev1/collaborations/HotSpringCyanobacteria.htm Microbial Mats At one time (over 3 billion years ago) the Earth’s flora and fauna consisted purely of microbial mats

3. http://www.cbs.dtu.dk/staff/dave/IconsReview.html

4. Across 600 million years of Phanerozoic evolution, the turnover of species was nearly total. More than 99 percent of all species that ever lived in each period perished, to be replaced by even larger numbers drawn from the descendants of the survivors.” (pg. 192) “The survival rate of species in this sequence is 1 in 2000.”

5. http://www.burgess-shale.bc.ca/ http://www.burgess-shale.bc.ca/menu.htm http://www.nmnh.si.edu/paleo/shale/ http://www.ucmp.berkeley.edu/cambrian/burgess.html

6. From E.O. Wilson 1992

7. http://stort.unep-wcmc.org/imaps/gb2002/book/viewer.htm Latitude Diversity Gradient

8. http://stort.unep-wcmc.org/imaps/gb2002/book/viewer.htm

9. http://stort.unep-wcmc.org/imaps/gb2002/book/viewer.htm

10. http://stort.unep-wcmc.org/imaps/gb2002/book/viewer.htm

11. Causes of Latitudinal Gradient in Richness Elizabeth Selig The latitudinal gradient in species richness is one of the oldest and most ubiquitous patterns in ecology. A peak in species richness at the equator is generally observed regardless of biota’s taxa, geographic context, or time domain. More than 30 hypotheses have been generated to explain the gradient. Many of these hypotheses have been debunked based on their circular logic, the lack of supportable evidence, or because they cannot be extrapolated beyond specific species or locations. Hypotheses can be categorized into four major groups: historical, environmental, biological, and spatial. In the past, research has focused on proving or disproving particular hypotheses, but recent research has begun to suggest that only a more synergistic, hierarchal model will explain the variation in the latitudinal gradient. Consequently, future work should investigate which hypotheses are primary drivers of the pattern and which are modifiers. http://www.bio.unc.edu/faculty/peet/courses/Bio255/handouts/nov25.htm

12. Recommended reading: Willig, M.R., D.M. Kaufman, and R.D. Stevens. 2003. Latitudinal gradients of biodiversity: pattern, process, scale, and synthesis. Annual Review of Ecology, Evolution, and Systematics 34: 273-309.

13. http://academic.evergreen.edu/n/nadkarnn/home.html http://www.science.uottawa.ca/bio/eng/prof/currie.html

14. Patterns in Richness * Latitudinal Gradient Gradient: continuous change in some characteristic over space or time * Richness, in general, increases as one approaches the equator * Examples from book: Birds, Reptiles, Ants, Molluscs, Crustaceans, Mammals * Since this pattern is so widespread, there are many ideas about why it occurs

15. Biotic Explanations -- change in richness depends on change in the interactions between organisms as one changes latitude * Spatial Heterogeneity Theory -- more plants in tropics mean more places for insects and vertebrates to live (notice no explanation for why there are more plants in the tropics in this theory). Also hard to explain why marine richness gradients occur with this theory * Competition Theory -- as you go north, abiotic conditions become more stressful and species are r-selected. In the tropics, species are K-selected and compete more. Competition reduces niche breadth for each species so that resources support more species. * Predation Theory -- The number of predators and parasites increases in low latitudes. Predators can prevent the competitive elimination of species by superior competitors if they depress the size of the population of the dominant competitor. A predator that acts to increase the number of species in the community is called a Keystone Predator (a keystone is the central stone in the arch which seems to hold the other stones in the arch in place - remove the keystone and the arch collapses, remove the keystone predator and the diversity of the community collapses * Pollinators Theory -- the lack of sustained winds in the tropics increases the importance of animal pollination. Coevolution between pollinator and plant species leads to specialization and an overall increase in the number of plant and pollinator species

16. * Abiotic Explanations -- looks for relationship between individuals and abiotic characteristics of environment for explanation of latitudinal gradient * Time Theory -- Time leads to the evolution of greater richness. The tropics have not been subject to glaciation and so have had a constant environment for longer than temperate and polar regions and so more species are found there due to evolution of new species. Some evidence that glaciated lakes have fewer species than non-glaciated lakes (when both are at the same latitude). * Productivity Theory -- Greater productivity (by autotrophs) means more energy is available to support more species. Productivity is greater in tropical terrestrial systems in general (longer growing seasons). This does not seem to apply as well as to some aquatic communities, especially when productivity is very great (Eutrophic lakes are those that have very high productivity of algae but they usually have low richness of algal types and of the invertebrate and vertebrate communities supported by the algae) * Area Theory -- It is well established that large areas have more species than do small areas. The book applies this to the latitudinal gradient, but you instructor thinks that there is no evidence that the tropics represent a larger areas of similar habitat than do some of the desert, forest, or grasslands found in the temperate zone. * Evolutionary Speed-- Greater species richness is the result of a greater rate of evolution in southern latitudes. This increased rate is due to increased temperature that lead to: shot generation times, higher mutation rates (unclear if this means on a per unit time basis or on a per replication basis), higher selection pressures (one of the basic tenets of evolutionary theory is that the rate of evolution is linked to selection pressure)

17. * Rapoport's Rule -- Northern species have wider ranges than tropical species (wider in terms of the degrees of latitude each species occupies). Rapoport felt that, if there were no differences in the dispersal of species, then individuals of northern species would find it easier to survive in more southern habitats, even if they could not permanently invade the south. Thus, tropical richness would be increased by the temperate species occurring there. There is little evidence that this phenomenon occurs outside of some very specific situations in which temperate species are found in tropical areas. The author, who resides in Florida, has ignored a significant counterexample from his own state. Dade County (where Miami is located) and the county to the south of Dade, have more species of trees than do all of the rest of North America (excluding Mexico). Why? Many tropical species live there after dispersing from the Caribbean area (although many do not successfully reproduce). Thus, Dade is a northern area enriched by dispersal from a southern area, just the opposite of Rapoport's Rule.

18. source populations: * good habitats * population size is growing * emigrants colonize other sites sink populations: * poor habitats * local populations are headed toward extinction * immigrants may constantly colonize site Emigration Immigration

19. Lognormal distribution

20. Effect of body size on diversity? “Hutchinson and MacArthur suggested that the number of species increases directly with a decrease in the area of the body of animals, or the square of their body lengths. The reason for this rule, they proposed, is that animals living on surfaces require spaces that are the square of their body lengths”. (pg. 207) A fractal world?

21. http://cgee.hamline.edu/see/crs_and_concept/see_essay_primer_10-11.htm#Interliving Microhabitats Weevil with a garden of lichen growing on its back

22. The species of mite seen here are ONLY found on the jaws of certain army ants http://www.lib.uconn.edu/about/exhibits/naturex3/rettenmeyer.htm Specialization