ICA 09 SPECIES DIVERSITY 2
Group ____________Name__________________
LOCAL DIVERSITY AFFECTED BY REGIONAL DIVERSITY
1. Figure 2. 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 3. What is used to provide evidence of a regional effect on local diversity?
Compare two very similar habitats in two regions; the difference in species diversity
between the two is the ‘regional effect’ on species diversity.
3. Figure 4. 21.14 Does local diversity ever reach regional diversity?
No; it levels off despite increasing regional diversity.
Figure 5. 21.15 Are these local communities saturated? Explain.
Local diversity continues to rise linearly with increasing regional diversity and does
not level off, so they are not saturated.
4. What is meant by an equilibrium theory?
One with processes that are in balance with one another, resulting in a equilibrium
number (e.g. of population size; of # species on an island; of # species on continent).
What processes add species? speciation and immigration
What processes subtract species? extinction and emigration
5. Figure 6. 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. (or Larger islands
are bigger targets for successful immigration).
6. Figure 7. 20.19 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 (colonization) curve? regional
extinction curve? local
Figure 8. 20.21 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.
Figure 9. 20.20 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 10. Which hypothesis is illustrated in 10A? Species diversity increases with
(island) area.
Why is the pattern altered in 10B? Islands are different distances from the mainland.
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? 21.23
1. speciation 2. immigration 3. mass extinction. 4. habitat heterogeneity
5. suitability of physical conditions 6. isolation from centers of diversity
10. Figure 12. What are three patterns in regional species diversity and what factor
accounts for each? 20.5
A. More species as decrease in latitude – climate less stressful.
B. More species in topographically heterogeneous western mountains.
C. Decrease in species down the Baja peninsula due to dispersal limitation.
11. Figure 13. 20.6 How do patterns of species richness differ among taxa? Why?
A. Trees: Increase from NW to SE with increasing moisture gradient.
B. Amphibians: same as trees.
C. Reptiles: Increase from N to S with increasing temperature gradient.
12. Figure 14 bottom. 21.16 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 14 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.
13. Figure 16. 21.17 What is the relationship between tolerance of low temperature
and/or rainfall and extinction? Extinct groups are tolerant of a wide range of
rainfall, but are intolerant of low mean annual temperatures.
LATITUDINAL SCALE
14. Figure 17. Describe the major latitudinal pattern of species diversity.
For most taxa, species diversity increases from the poles to the equator.
The hypotheses in ICA 08 that explain local diversity were derived by thinking
about why the tropical biome has the greatest species diversity.
What must be true of these 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 in the tropics? 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. However,
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
15. Figure 18. 20.23 What determines the equilibrium # of species S(hat) on a
continent? The balance between speciation and extinction rates on a regional scale.
16. Figure 19. 21.19 How does the hypothesis about the speed of diversification
explains greater species richness in tropical than temperate regions? Stability may
have led to speciation proceeding rapidly compared to extinction (diversification
increases more rapidly) in the tropics than the temperate zone.
17. Figure 20. Has diversity been constant for long periods? Yes
Have mass extinctions occurred – in marine invertebrates? Yes terrestrial plants? No
What is the relative role of extinction vs. additions on diversity of these groups?
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.
Figure 21. 21.21 In more recent times did plant diversity increase overall? No
What environmental factor correlated well with pattern of plant diversification?
global average temperature
If all species ‘turned over’ during this period, what processes contributed to the
number of species being the same at beginning and end of this figure? Continual
diversification and extinction.
18. Figure 22. What are some general consequences of catastrophes for species diversity on:
short: major losses via extinction.
long time frames? fosters rapid evolutionary responses to new types of conditions.
They create opportunities for development of new types of biological associations.
GLOBAL
19. Figure 23. 21.4 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.
Figure 24. By what means did continental drift change routes of dispersal?
What are some examples? 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)
Figure 25. 21.6 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.
Figure 26. 21.7 How did the new land bridge affect N and S American mammal
diversity?
Early migrations were S to N, but later were primarily N to S; those N lineages
diversified and may have caused the extinction of many S.A. endemics.
Figure 27. 21.5 How do birds of the same body form occur on separate continents?
They have a common ancestor that developed on Gondwana before the
Southern continents separated. After separation the body form was largely retained
with diversification of minor modifications on the fragmented continents.
20. Figure 28. 21.18 How has climate changed the relative size of biomes over time?
Tropical climates were much more extensive during the Eocene and slowly
contracted . Boreal biome is relatively recent. Present-day species richness of trees
is predicted better by area occupied by these forest types during the past than by their
area at present.
Figure 29. 21.20 Where does more diversification occur? In ecological zone of origin.
Why? Adaptive shifts to a new ecological zone are more difficult as they face more
stressful conditions, and hence are infrequent. Since evolution has had more time to
operate in the tropics and a large proportion of ancestral lineages were adapted to
tropical conditions, then decrease in species richness with latitude may be explained
by this phenomenon.
21. Figure 30 + 31. Give an example of how climate change plays a role in explaining
species diversity in North America: In Miocene with warmer, drier conditions,
grasslands spread with an accompanying increase in herbivore species richness.
in Europe: 21,9 Oak species shifted south to a few refuges during glacial period,
then expanded N after glaciers receded to reach their maximum extent about 6000
yrs ago.
Figure 32. 21.10 How does ‘dispersal limitation’ explain differences in post-glacial
expansion of tree species in Europe? Small-seeded species spread far N after the
glaciers receded, but the large-seeded species faced dispersal limitation and are in
more S areas of Europe.
22. Figure 33. 21.8 How does climate history determine species distributions and affect
community composition? 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 and
community types.