ICA 2 SPECIES DIVERSITY 2 Group ____________Name__________________
LOCAL AFFECTED BY REGIONAL
1. Figure 1. Describe this non-linear relationship between regional and local diversity.
A concave curve exists; as regional div increases, local does too but at a lower level.
2. Figure 2. Does local ever reach regional diversity?
No; it levels off despite increasing regional diversity.
Figure 3. Are these local communities saturated? Explain.
Local diversity continues to rise linearly with increasing regional diversity and does not level off.
3. What is meant by an equilibrium theory?
One with processes that are in balance with one another.
What processes add species?
speciation and immigration
What processes subtract species?
extinction and emigration
4. Figure 4. Describe what predicts S(hat): the equilibrium number of species on an island.
When the rate of immigration equals the rate of extinction, an equilbrium of species number is reached.
What is the spatial scale for the immigration curve?
curve? 5. Figure 5. How/why is island biogeography theory modified by proximity to mainland?
S(hat) is greater for islands near than far to the mainland because of greater dispersal potential.
6. Figure 6. How/why is it modified by size of island?
S(hat) is greater with larger than smaller islands because of lower extinction rates on large islands.
7. Figure 7. What is the pattern?
Species # increases as island size increases.
What two factors may explain it?
More habitat heterogeneity on larger islands yields more niches/less competitive exclusion (extinction) and more species. Larger islands have larger population sizes less prone to stochastic extinction.
8. How can the Theory of Island Biogeography be applied to land ‘islands’?
Any land area surrounded by greatly contrasting habitat can be considered an island. Such islands will vary in size and proximity to source area for immigration to island. REGIONAL SCALE
9. What are 6 factors that may explain regional-scale patterns of diversity? 1.
speciation 2. immigration 3. mass extinction. 4. habitat heterogeneity 5. suitability of physical conditions 6. isolation from centers of diversity
10. Figure 8. What are three patterns in regional species diversity and what factor accounts for each? A.
More species as decrease in latitude – climate less stressful.
More species in topographically heterogeneous western mountains.
Decrease in species down the Baja peninsula due to dispersal limitation.
11. Figure 9 bottom. What are major changes among regions from Tertiary to present? What accounts for changes?
NA had fewer genera than E and A in T. Today E has many fewer genera than A and slightly fewer genera than NA. Glacial periods pushed flora S to safe refugia in NA, but in E the flora was trapped by the Alps and couldn’t jump the Mediterranean so many genera went extinct.
Figure 9 top. What are major differences today among regions? What accounts for differences?
A has many more species than NA and especially E and has many more tropical species than either E or A. A is connected via moist land to tropical regions, while NA has a desert between it and tropical regions. E has Mediterranean Sea and Sahara desert between it and tropical regions. LATITUDINAL SCALE
12. Figure 10. Describe the major latitudinal pattern of species diversity.
For most taxa, species diversity increases from the poles to the equator.
The hypotheses in ICA 1 that explain local diversity were derived by thinking of why the tropical biome has the greatest species diversity. What must be true of the 5 hypotheses for them to explain the latitudinal pattern?
They must be more ‘intense’ processes than in the temperate zone.
How does TIME contribute to more species?
It refers to a long period of stability without climatic disruption, allowing much time for speciation and low amounts of extinction, resulting in a high species diversity in the tropics.
How much support is there for the time hypotheses?
The tropics may also have been affected by glacial history – with dry periods during cold periods to the N. The tropical climate has not been stable. CONTINENTAL SCALE
13. How is the equilibrium theory applied to continental-scale communities?
If regional diversity has been stable then it contributes to continental-scale accumulation of species.
What determines S(hat) on a continent?
The balance between speciation and extinction rates on a regional scale.
14. How does history and geography affect current day patterns of diversity – independent of local environmental conditions? Consider marsupials in Australia.
They affect species diversification. If histories of continents are different, then so will their species diversity. Australia’s unique fauna is constrained by the characteristic of their ancestors. Some lineages, such as marsupials, are preserved even in the face of environmental change.
15. Figure 11. Has diversity been constant for long periods?
Have mass extinctions occurred – in marine invertebrates?
What is the role of extinction vs. additions?
Diversity of marine invertebrates has been greatly affected temporarily by a mass extinction, but additions via speciation have more than replaced extinctions so their species diversity has continued to rise.
What caused the very rapid rise of terrestrial plants?
The diversification of flowering plants.
16. Figure 12. What are some general consequences of catastrophes for species diversity on short- vs. long-time frames?
Short-term = major losses via extinction. Long-term = fosters rapid evolutionary repsones to new types of conditions. They create opportunities for development of new types of biological associations.
17. What is continental drift?
movement of continents on plates over geological time.
How would it affect climate?
Continents move to different latitudes with different angles of sun, affecting temperature and rainfall. They change in amount of contact with large bodies of water affecting specific heat and heat transfer to land.
18. Figure 13. How did birds of the same body form on so many separate continents arise?
They have a common ancestor that developed on Gondwana before the Southern continents separated. After separation the body form was largely retained with minor modifications on the fragmented continents.
19. Figure 14. By what means did continental drift change routes of dispersal? What are some examples of each?
Separation (e.g. Africa and S.A.; N and S America; Australia, SA and Antarctica). Joining (e.g. Europe and Africa; India and Asia; Australia and SE Asia)
20. Figure 15. What explains the major zoogeographic regions of the world?
The unique fauna of each region reflects its long-term evolutionary isolation of large areas because of continental drift. Subsequently, each region developed distinctive characteristics independently of changes in other regions.
21. Figure 16. Give an example of how climate change plays a role in explaining species diversity.
During cool-down and warm-up from glacial periods, tree species had different starting and ending points. Each migrated independently of other species and different regions ended up with different species composition.