OBJECTIVES

• Species Diversity at scales above local

• Regional effects on local SD

• Equilibrium theory + Island Biog. Theory

• Regional SD

• Latitudinal SD

• Continental SD

• Global SD

What explains great variation in species richness over the earth?

Figure 1

Multiple scales of species diversity

• Local

• Regional

• Latitudinal

• Continental

• Global

Many factors influence regional and localspecies richness.

Local diversity as f (regional diversity).

Figure 2

Comparing diversities of communities in similar habitats in different regions can reveal regional effects.

Figure 3

Saturation of local communities hypothesis: test how local and regional diversity relate.

Figure 2Figure 4

Variation in local species diversity depends on regional diversity.

***Are these local communities saturated?

Figure 5

Equilibrium theories: diversity reflects a balance between processes that add vs. remove species.• ***What processes add species?• speciation• immigration

• What processes subtract species?• extinction• emigration

• Differences in diversity between communities reflect differences in relative rates of these processes.

*** What is the pattern? What two equilibrium factors may explain it?

Figure 6

Equilibrium theory of island biogeography:# species = balance of immigration on a regional scale vs. extinction on local scale.

Figure 7

Islands closer to the mainland support more species because of higher immigration rates.

Figure 8

Larger islands support more species because of lower extinction rates.

Figure 9

Which hypotheses are illustrated in Figure (a) + (b)?

Figure 10

*** Do experimental results support ETIB?

Figure 11

Applications of Island Biogeography Theory to:

• Terrestrial systems

• mountain tops as islands

• fragmented remnants as islands

• Design of nature reserves

Regional-scale patterns of diversity also reflect:

• Habitat heterogeneity

• Suitability of physical conditions

• Isolation from centers of diversity

***What are three patterns in regional species diversity? What factor accounts for each pattern?

Figure 12

How do patterns of species richness differ among taxa? Why?

Figure 13

***What are major changes among regions from Tertiary to present? What accounts for them?What are majordifferences today?

Figure 14

***Why did climate change during the Ice Age contribute to Europe’s low species richness?

Figure 15

Figure 15

What is relationship between tolerance of low temperature / rainfall and extinction?

Figure 16

Multiple scales of species diversity

• Local

• Regional

• Latitudinal

• Continental

• Global

***What is latitudinal gradient in woody species diversity? What explains it?

Figure 17

Hypotheses to explain latitudinal gradient in species diversity…

• Time and stability

• Heterogeneity in space and time

• (Vegetation and food complexity)

• Herbivore and pathogen pressure

• Competition/niches

• Disturbance

Multiple scales of species diversity

• Local

• Regional

• Latitudinal

• Continental

• Global

How do history + biogeography + climate change influence species diversity?

History of life is gauged by geologic time scale.

Cretaceous 150mya

Cambrian 600mya --> Permian 286mya

Equilibrium theory in continental communities: balance between speciation and extinction on regional scale

Figure 21

Has diversification been faster in tropicsthan temperate area?

Figure 22

***Has diversity been constant? What is role of extinction vs. additions?

Figure 18

Did species richness increase through time?To what did richness correspond?All species turned over during this time period.

Figure 19

Catastrophes --> what are consequences - short- and long-term?

***Asteroidimpact-->extinctionsof what?

Figure 20

Multiple scales of species diversity

• Local

• Regional

• Latitudinal

• Continental

• Global

Continental drift --> positions of continents change over geologic time.Climate changes too --> influences geography of evolution

Figure 23

Continental drift changed routes of dispersal via separation + joining.

Figure 24

Wallace: Major zoogeographic regionsreflect long-term evolutionary isolation.

Figure 25

Exchanges of biotas after joining of continents: e.g. The Panama land bridge

Figure 26

***How explain same body form in multiple continents?

Convergence ordivergence?

Figure 27

Climate change influences distributions oforganisms. How does the historical extent of climate zones help to explain global patterns ofspecies richness?

Figure 28

Where does more diversification occur?Why? How does this relate to more speciesnear 0 than at higher latitudes?

Figure 29

Climate change in N.A. shifted species diversity; Miocene drier with grasslands.

FigFigure 30

Oak trees shifted their distributions afterend of most recent glacial period.

Figure 31

How does ‘dispersal limitation’ explain differences in post-glacial expansion?A,b = small; c,d = large seeded species

Figure 32

How doesclimatic historydeterminespeciesdistributions +communitycomposition?

Figure 33