Lecture 16: Biogeography

Question 1

Biogeography

Answer 1

the study of patterns of species composition and diversity across geographic locations.

Question 2

Lower Latitudes vs higher latitudes

Answer 2

• Lower have many more, and many different species than higher latitudes

Question 3

Species richness

Answer 3

• The same community type or biome can vary in species richness and composition depending on its location on Earth.

Question 4

Spatial scales

Answer 4

• are interconnected in a hierarchical way, with the patterns of species diversity and composition at one spatial scale setting the conditions for patterns at smaller spatial scales

Question 5

Global scale

Answer 5

• entire world
• Species have been isolated from one another, on different continents or in different oceans, by long distances and over long periods
• Rates of speciation, extinction, and dispersal help determine differences in species diversity and composition

Question 6

Regional scale

Answer 6

• areas with uniform climate; the species are bound by dispersal to that region

Question 7

Regional species pool

Answer 7

• all the species contained within a region (gamma diversity)
• Provides the raw material for local assemblages and sets the theoretical upper limit on species diversity for communities
• All species available that can live in the habitats

Question 8

Landscape

Answer 8

• Topographic and environmental features of a region
• Species composition and diversity vary within a region depending on how the landscape shapes rates of migration and extinction.

Question 9

Local scale

Answer 9

• equivalent to a community
• Species physiology and interactions with other species are important factors in the resulting species diversity (alpha diversity)

Question 10

Beta diversity

Answer 10

• Change in species number and composition, or turnover of species, from one community type to another

Question 11

Global Biogeography

Answer 11

Global patterns of species diversity and composition are controlled by geographic area and isolation, evolutionary history, and global climate
- Some species in one part of the world are similar to species in another part

Question 12

Two global patterns

Answer 12

• There is a gradient of species diversity with latitude (higher latitudes, diversity goes down)
• Earth’s land mass can be divided into six biogeographic regions

Question 13

Vicariance

Answer 13

evolutionary separation of species by barriers such as those formed by continental drift
ex. The large flightless birds (ratites) had a common ancestor from Gondwana. After isolation on different continents, they evolved unique characteristics, but retained their large size and inability to fly.

Question 14

Global patterns of species richness should be controlled by which three processes?

Answer 14

• Speciation
• Extinction
• Dispersal (if rates are similar everywhere, then species richness should reflect a balance between extinction and speciation)

Question 15

Species Diversification rate

Answer 15

• The net increase or decrease of species over time
• Subtracting extinction rate from speciation rate

Question 16

Species diversification time

Answer 16

• The tropics are thought to have been more climatically stable over time, and species have had more time to evolve.
• Temperate and polar regions have undergone severe climatic changes such as glaciation, disrupting species diversification.

Question 17

Productivity or carrying capacity

Answer 17

• Higher carrying capacity and productivity in the tropics (terrestrial)
• some very productive habitats, such as estuaries, have low species diversity

Question 18

Regional Biogeography

Answer 18

Regional differences in species diversity are influenced by area and distance, which determine the balance between immigration and extinction rates
- species richness increases with area sampled

Question 19

Species–area curves

Answer 19

• plots species richness (S) of a sample against area (A) of the sample.
• The relationship between S and A is estimated by linear regression: S = zA+c
• z=slope, c=y-intercept
• S and A are transformed into logarithmic values to obtain a straight line

Question 20

Island sizes

Answer 20

• large islands have more species than small islands
• Larger islands closer to mainland, smaller islands further away
• Populations on small islands have higher chances of going extinct, due to small population size and increased effects of competition and predation.

Question 21

The equilibrium theory of island biogeography

Answer 21

• The number of species on an island depends on a balance between immigration or dispersal rates and extinction rates
• This equilibrium number is the number of species that should theoretically “fit” on the island, irrespective of the turnover, or replacement of one species with another

Question 22

The Biological Dynamics of Forest Fragments Project

Answer 22

• Explains why more species are found on large islands than on small islands
• Four different sizes of forest plots were set up: 1, 10, 100, or 1,000 hectares.
• Control plots were surrounded by forest. Fragments were surrounded by logged land.
• Study design of conservation reserves and maintenance of species diversity
• project shows that most forest fragments are too small to maintain all their original species. Habitat fragmentation is likely to result in the loss of many species

Question 23

Habitat fragmentation

Answer 23

• creates large edge effects at the transition between forest and matrix habitat (can contribute to local extinctions)
• ex. trees at the edge are exposed to more light, higher temperatures, wind, fire, and diseases.

Question 24

Edge effects & forest regenerates

Answer 24

• If forest regenerates, secondary succession takes place and edge effects decrease
• if not, the area subjected to edge effects may increase in size

Question 25

Burning of forests

Answer 25

• Burning is used regularly and keeps the forest edges in a constant state of disturbance. Fire-tolerant species increase and edge effects extend into the fragment, reducing its effective size
• In order to have forest practices to maintain species richness, need to set aside massive fragments to preserve