1. Remaining Schedule Essay #2 (undergraduates) –Drafts returned over the next several days --you have a full week to return final version to Katie –Please schedule appointment (in person, by phone, by skype) to meet with Katie early next week to discuss writing (Monday especially open) January 15th: last lecture Sunday, Jan 18th: Review for final exam –Streamed live, then available on the course website –Distance students email questions to Alex in advance or during review –Review questions sent to you within next few days Jan 22nd: Final exam –Similar format as midterm –Distance students: need to arrange proctor

2. Patterns & Determinants of Species Richness Diversity indices Alternative hypothesis for species richness: resources, niche breadth and niche overlap –Productivity and resource richness –Predation intensity –Spatial heterogeneity Temporal variation and species richness –Climatic variation –Disturbance –Evolutionary time Theory of Island Biogeography Gradients in species richness –Latitudinal –Altitude & depth –Community succession Patterns in species richness through time –Fossil record –Human disturbance

3. Community assemblage is determined by: - dispersal constraints - environmental constraints - internal dynamics

4. Description & Properties of Communities Descriptors - list of species - graphs of species richness - indices of species diversity (incorporate relative abundance)

5. Diversity Indices & Rank-Abundance Diagrams The Rothamsted pasture experiment (1856-1949) Shannon-Weaver diversity index, H, = sum of the P i lnP i - H confounds richness & evenness Rank-Abundance curves show increasing domination over time by the commoner species (steeper curves)

6. A model based on niche overlap & breadth -higher species diversity because: a) > range of resources, R Competition dominates: (b) more specialized (smaller average niche breadth, n) Predation may keep species below their K’s: c) > resource overlap, o but… predation may alternatively exclude prey d) R more fully utilized

7. Species richness may increase with productivity because: 1) wider range or resources; 2) higher rate of supply; &/or 3) rare resources increase to support additional specialized populations Productivity & NA tree species richness a) Potential Evapotranspiration (PET) b) PET & )Rainfall (PET reflects energy availability: water potentially evaporating or transpiring) Points are 336 quadrats N of Mexico defined by lines of lat. & long.

8. NA Vertebrate Species Richness & PET (= temp): ectotherms might need more energy, endotherms use less energy/individual? - > E for growth -> larger populations -> narrower niches

9. Productivity & Diversity a) + correlations for ants & rodents in SW Amer. Deserts b) fish in NA lakes (but recall Rothamsted! “the paradox of enrichment may lead to competitive exclusion, so expect humped curves, as per: b) phytoplankton in NA lakes & c) desert rodents in Israel but cannot generalize across taxa and communities: d) humped curves more common in plant comparisons, but more positive relationships with animals

10. How many animal species can coexist? resource diversity enables differences in feeding efficiency - travel costs - handling efficiency - detoxification - energy needs …niche specialists therefore outcompete generalists but… must harvest enough resources to maintain some minimal population density

11. Periods of low productivity can restrain guild species diversity… …. but habitat diversity can allow > population density & > niche specialization among frugivores through habitat switching Peat Lowland

12. …and > niche specialization among frugivores possible because alternative foods available in fruit-poor periods - preferred, specialized hornbill fruits are rare … but can switch to figs as always available because of pollinating fig wasp mutualism

13. Predator-mediated coexistence of prey species: predation or grazing can interrupt competitive exclusion 0= no grazing, 1=light, etc. 4=very heavy grazing

14. Intermediate densities of periwinkles maintain high algal diversity in New England tide pools - Enteromorpha alga competitively exclude other species at low densities - At high densities, periwinkles broaden diet - effect is due to preference for competitive dominant

15. Keystone Predators: Paine’s Pisaster starfish exclusion experiments Mytilus mussels outcompeted other space-holding spp, reducing species diversity from 15 -> 8 Starfish prefer to feed on the dominant mussels & barnacles

16. The hemiparasite Rhinanthus minor suppresses growth of hosts & prevents competitive exclusion by dominants Applying exploiter-mediated coexistence to manage grassland species richness

17. Diversity & Environmental Spatial Heterogeneity a) plant diversity weakly increases with index of topography & soil near Hood River, Canada b) removing needles from Doug fir branches reduced spider species diversity c) fish diversity was higher in Wisconsin lakes with more diverse vegetation types d) arboreal ant richness higher with Brazilian savanna tree diversity

18. “harsh environments” must limit the number of species that are adapted to them…but is low species richness due to low productivity? a) Alaskan tundra plant spp & pH b) Stream inverts, Ashdown Forest, England

19. Temporally varying factors influencing species richness - predictable seasonal variation might require diverse adaptations, and be “partitioned” Range of monthly mean temperature along west coast of N. America & diversity

20. The Intermediate Disturbance Hypothesis a) algae on intertidal boulders; b) NZ steam insects; c) German lake phytoplankton

21. Species-area relationships Lack’s hypothesis: Larger islands have more habitats & resources Left: plants on cays near Bahamas Right: birds on Florida lakes Left: bats in Mexican caves Right: fish in Australian desert springs

22. Equilibrium Theory of Island Biogeography The accumulation of species on islands is stochastic (= probablilistic) and not deterministic--- it is uncertain which species colonizes an island (establishes a population) or goes extinct The rate of arrival of lucky breeding individuals, pairs or groups should depend on both island area (bigger target) and on distance from the colonizing source (continent or bigger island) As species accumulate on the island, competition for resources increases, so the average sizes of these populations will decline Populations fluctuate, and the annual risk of extinction depends on population size; therefore, as species accumulate, the rate of extinction will increase source far Colonizing pair

23. MacArthur & Wilson’s Theory of Island Biogeography - rates of either a) immigration or b) extinction vary with no. resident species on island - curve of immigration declines with island area & distance from colonizing source - risk of extinction depends on population size, so related to habitat area -no. of species on the island fluctuates; equilibrium occurs when two rates are equal

24. Simberloff’s test of the equilibrium theory: isolating effect of area from habitat diversity - Arthropod species changes on mangrove islands off the coast of Florida - islands 1 & 2: reduced in size each year; #3 only after 1969; control unchanged

25. Integrating effects of habitat diversity and area: top: herbivorous (circles) and carnivorous (triangles) beetles of Canary Islands (note: habitats are plant species) proportion of variance in spp richness explained by different factors for four animal taxa of the Lesser Antilles islands

26. Distance from a colonizing source also influences the equilibrium number of species: birds on S. Pacific Islands Colonization takes time: increase in species on the new volcanic island of Surtsey, formed in 1963 near Iceland Each island is plotted as ratio of its bird species to island of similar size but near to New Guinea source (the “saturated island”) (Diamond 1972)

27. The Tropics are rich in species in most taxa left: marine bivalves right: swallowtail butterflies left: N. Am. mammals right: N.A. trees hypotheses: a) >predation & reduced competition b) climatic stability c) productivity d) evolutionary time …. unclear Latitudinal Gradients in Species Richness

28. Not all tropical taxa are more specialized (ambrosia & bark beetles combined)

29. Altitudinal Gradients a) Himalayan breeding birds b) Plants in Mexican mountains c) Ants in Spring Mtns., Nevada d) Plants in Nepalese Himalayas

30. Species Richness Gradient with Depth in Lakes and Oceans - large lakes- deep, dark and cold water poor in productivity & in species - marine: plants restricted to shallower photic zone, but can have high diversity on ocean floor However, on continental shelf ocean floor (benthos), diversity peaks at about 1 km deep -> environmental stability there? (Megabenthos SW of Ireland)

31. Species richness increases during early succession a) birds after shifting cultivation (India) b) Bugs in old field succession

32. Taxon richness through the fossil record top: marine invertebrates vascular land plants insects bottom: amphibians reptiles mammals

33. Pleistocene extinctions % genera herbivorous mammals % large animals surviving going extinct in last 130,000 yrs & arrival of human huntersmammals Africa Australia N. America Madagascar & New Zealand

34. Alien flora of British Isles: by community type -disturbance -near human settlements by geographic origin; explained by: - proximity -trade patterns -climatic similarity Exotic species are associated with humans