1. Biodiversity Gradients

2. Class Outline Biodiversity Latitudinal patterns of biodiversity
Processes and explanations
Other spatial patterns of biodiversity

3. What is Biodiversity?
Genetic Biodiversity: The diversity of gene allotypes within a single species.
Ecological Biodiversity: The diversity of different species within a community

4. Genetic Diversity

5. Ecological Diversity

6. What is Ecological biodiversity?
Species richness: the number of species per unit area
Species abundance: number of individuals per species per unit area
Species diversity: number of different species in a particular area weighted by some measure of abundance
But, species diversity is often used as a synonym of species richness

7. Importance of Biodiversity
Biodiversity boosts ecosystem productivity where each species, no matter how small, all have an important role to play.
A healthy biodiversity provides a number of ecological services for everyone

8. Ecological Services: Ecosystem services, such as
Protection of water resources
Soils formation and protection
Nutrient storage and recycling
Pollution breakdown and absorption
Contribution to climate stability
Maintenance of ecosystems
Recovery from unpredictable events
Biological resources, such as
Food
Medicinal resources and pharmaceutical drugs
Wood products
Ornamental plants
Breeding stocks, population reservoirs
Future resources
Diversity in genes, species and ecosystems
Social benefits, such as
Research, education and monitoring
Recreation and tourism
Cultural values
Ecological Services:

9. Biodiversity Only about ~2mill recognized species
About half are insects and almost 25% are represented just by beetles!
Estimated 8.7 mill species (Mora et al. 2011)

10. Biodiversity
About 10,000 new species are found every year (mostly insects and other invertebrates)
New vertebrate species are still being discovered (about 1‐5 birds and 1‐5 mammals per year)
Burrunan dolphin
Darwin’s Bark Spider

11. Lesula Lowland rainforests Documented by scientists in 2007
Known to locals long before that

12. Wollemi pine (Wollemia nobilis)
Araucariaceae family
Discovered in 1994
< 100 trees exist

13. Scales of biodiversity
Biodiversity can be measured and monitored at several spatial scales.
Alpha Diversity = richness and evenness of individuals within a habitat unit. For example in the figure below, Alpha Diversity of Site A = 7 species, Site B = 5 species, Site C = 7 species.
Beta Diversity = expression of diversity between habitats. In the example below, the greatest Beta Diversity is observed between Site A and C with 10 species that differ between them and only 2 species in common.
Gamma Diversity = landscape diversity or diversity of habitats within a landscape or region. In this example, the gamma diversity is 3 habitats with 12 species total diversity.

14. Which sites have highest alpha diversity?
Between which regions have highest beta diversity?
What is the gamma diversity?

15. Latitudinal patterns of biodiversity
Increasing species richness from the pole to the equator
One of the most widely recognized (and studied) patterns in biogeography

16. Latitudinal patterns of biodiversity

17. Latitudinal patterns of biodiversity
Observed for all species combined and also for individual taxa
Ancient pattern (~100 my old)

18. Spatial patterns of biodiversity
Terrestrial mammals

19. Swallowtail butterflies
Spatial patterns of biodiversity
Swallowtail butterflies

20. Latitudinal patterns of biodiversity
Changes are not constant over latitude
Several exceptions
General pattern is clear
and well supported by evidence

21. Spatial patterns of biodiversity
Amphibians

22. Biodiversity and Elevation
Elevation gradients
Species richness tends to increase with elevation until a certain threshold and then decreases

23. Biodiversity and Elevation
Causes vary depending on the species
Environmental factors
Temperature
Air pressure (oxygen)
Precipitation

24. Biodiversity and Peninsulas
Peninsula effect: Decreasing species richness toward the tip of peninsulas
Smaller area – higher extinction Isolation position – less immigration

25. Processes and explanations
First explanations:
Forster (1778): higher heat intensity in the tropics
Wallace (1878): increasing severity of climates towards the poles

26. Processes and explanations
Lots of research aimed at explaining this pattern
This topic was among the 25 key research themes for the future (in the 125th anniversary issue of Science, 2005)

27. Processes and explanatio ns
Multiple Hypotheses ns
Abiotic
Environmental stability
Antiquity of the tropics
Area
Glacial fluxes
Biotic
Habitat heterogeneity
Productivity
Competition
Geographic ranges (Rapoport's rule)

28. Environmental stability and predictability
Abiotic Explanations
Environmental stability and predictability
Tropics tend to be more stable over short and long time scales – fewer extinctions, more specializing for predictable environments

29. Antiquity of the tropics
Abiotic Explanations
Antiquity of the tropics
Tropical biomes have existed for longer time periods compared to higher latitude biomes; therefore, tropical regions have accumulated more species than other high latitude areas

30. Abiotic Explanations Area
The tropics occupy more area on Earth than other regions and biodiversity is known to increase with area
Why would biodiversity increase with area habitat?

31. Abiotic Explanations Glacial fluxes
Glacial expansions in the Pleistocene caused extinctions in high latitude regions
Insufficient time to return to the original biodiversity levels of these regions

32. Biotic Explanations Habitat heterogeneity
Generally, higher species richness levels are associated with heterogeneous habitats; and tropical areas tend to be more heterogeneous than high latitude biomes

33. Biotic Explanations Productivity
Higher productivity levels in tropical areas provide more energy to support more species of primary consumers (and more predators too)

34. Biotic Explanations Competition
By keeping populations of species at low levels, competition allows more species to coexist in competitor‐rich tropical communities

35. Geographic ranges (Rapoport’s rule)
Biotic Explanations
Geographic ranges (Rapoport’s rule)
Tropical species tend to have smaller geographical ranges  more species can coexist in tropical than in temperate regions

36. Processes and Explanations
Integrative explanations
Speciation, extinction, and immigration (Wiens and Donoghue, 2004)
Tropics are older and larger  higher speciation and lower extinction rates
Tropics are more benign and productive  species become specialists and have limited dispersal

37. Evaluating processes and explanations
Different processes act at different scales
Combination of explanations is important
Important difference between maintenance and
creation of biodiversity
Which processes maintain vs. create?