1. Bird species (left), mammals (right)

2. Diversity theory How is diversity defined?
What are the correlates of diversity?
Why do the tropics have more species?
What are some of the formal theories to explain diversity patterns?
What are the relationships between diversity and stability?
How will ecosystems respond to declines in diversity?
What are the shortfalls that beset a broad understanding of biodiversity – what is it we need to know?

3. Defining diversity As evenness and richness As taxonomic diversity
As alpha, beta, and gamma diversity
As balance between extinction and speciation or identification
As genetic diversity
As phylogenetic diversity
As functional diversity and phenotypic diversity
As interaction diversity

4. As evenness and richness
Low evenness: elephants dominant (Lower diversity)
Equal richness-same number of species (10)
High evenness (Higher diversity)

5. As taxonomic diversity
Species diversity is an example of taxonomic diversity
But there are other taxonomic hierarchies:
Kingdom, Phylum, Class, Order, Family, Genus, Species
Thus one can measure species diversity, or family diversity, or class diversity, or different taxonomic levels at once

6. As alpha, beta, and gamma diversity
Alpha (or local) diversity expresses the number of species within a given habitat. It is the most common way that diversity is employed
Beta (or turnover) diversity expresses the difference, or turnover, in species from one habitat to another.
Gamma (or regional) diversity-total number of species observed in all habitats within a geographic area

10. As genetic diversity
That are different genetic characteristics to measure
Genetic diversity can be calculated for a group of organisms based on:
The variability in nucleotide sequence (A, G, C, T) along specific regions of DNA
The richness and evenness of particular genes or proteins

11. As phylogenetic diversity
Diversity arising from differences in species lineages based on their evolution

12. As functional and phenotypic diversity
Function is often highly correlated with phenotype

13. As interaction diversity
A measure of the evenness and richness of the kinds of biotic interactions (competition, predation, parasitism, or facilitation) for a group of organisms

14. So how do I work with all these definitions for diversity?
It is common to measure and integrate multiple kinds biodiversity – taxonomic, phylogenetic, and functional

16. Correlates of biodiversity
Area
Disturbance
Habitat heterogeneity
Isolation
Latitude

17. Area: the species-area relationship
As area increases, so does the number of species. Originally applied to
the study of oceanic islands but is applicable to terrestrial islands as well.

18. Area: the species-area relationship
Species-area relationships are often graphed for islands (or habitats that are otherwise isolated from one another, such as woodlots in an agricultural landscape) of different sizes

19. Disturbance
The Intermediate Disturbance Hypothesis predicts that diversity in will peak
at intermediate disturbance frequencies. IDH is a very general model to explain diversity, and holds true in some habitat types than others.

20. Habitat heterogeneity
Greater heterogeneity in habitat can contribute to high biodiversity. For example, the most biodiverse states are those that have a large number of habitats, such as California.

21. Isolation
Isolation facilitates speciation, as evidenced in the unique flora and fauna of isolated islands like Hawaii, the Galapagos, New Zealand

22. Latitude
Plant species richness peaks in the tropical latitudes, as do some animal taxonomic groups. But what is it about latitude that creates this pattern?

23. Why do the tropics have so many species?
Theories to explain the large-scale latitudinal gradient in species diversity:
Climate stability hypothesis
Geographical area hypothesis
Species-energy hypothesis
Historical perturbation hypothesis
Evolutionary rate hypothesis
Tropical refugia hypothesis
Middle domain effect

24. Tropical refugia hypothesis
Suggests that the fragmentation of the rainforests during dry, cooler glacial periods of the Pleistocene created refugia of species-rich forest, which underwent subsequent speciation due to their isolation
This increased the pool of available species for dispersal and recolonization when glaciation ended.
Speciation has occurred for some species during the Pliestocene, while other species were present before the climate fluctuations of the Pleistocene
TRH has been rejected, but new genetic evidence is calling this rejection into question

25. Mid-domain effects Emphasizes that the geometry of species ranges
contributes to patterns
of diversity.