Ecology - Island Biogeography

Question 1

What is biogeography?

Answer 1

the study of distribution of living organisms and the reasons for those distributions

Question 2

Who is the “father of biogeography”?

Answer 2

Alfred Russel Wallace (1823–1913) is the father of biogeography!

Question 3

Who is the co-author of the theory of evolution by natural selection?

Answer 3

Darwin

Question 4

Wallace’s Line pass passes through two islands in what country?

Answer 4

Indonesia

Question 5

What are Wallace’s six biogeographic regions (realms) and where are they located

Answer 5

(1) Nearctic (North America & Greenland)
(2) Neo-Tropical (South America)
(3) Ethiopian (Africa)
(4) Palearctic (Most of Northern Asia)
(5) Oriental (Most of Southern Asia)
(6) Australasian (Australia & New Zealand)

Question 6

Describe the process of seafloor spreading.

Answer 6

mid-ocean ridges, molten rock flows from the seams between plates and cools, creating new crust and forcing the plates to move apart

Question 7

What are some of the results of subduction zones of the continental plates?

Answer 7

earthquakes, volcanic activity and the formation of mountains

Question 8

About 250 million years ago all the land masses on the Earth were joined in a “supercontinent” named _________.

Answer 8

Pangea

Question 9

After that, the “supercontinent” split into what two land masses?

Answer 9

Laurasia to the north and Gondwana to the south

Question 10

After that Gondwana split into what present-day regions of the Earth?

Answer 10

present-day South America, Africa, India, Antarctica and Australia

Question 11

Laurasia then split into what regions of the Earth?

Answer 11

North America, Europe and Asia

Question 12

North America was originally part of ________, while South America was part of ___________

Answer 12

Laurasia
Gondwana

Question 13

The Nearctic and Palearctic were both part of ancient________________.

Answer 13

Laurasia

Question 14

What is vicariance and what causes it?

Answer 14

refers to the evolutionary separation of species by barriers such as those formed by continental drift (i.e., long-term processes)

Question 15

How can the legacy of continental drift can explain the distribution of extant and fossil ratites?

Answer 15

the fossil record and in existing taxonomic groups such as the large flightless birds (ratites) had a common ancestor from Gondwana

Question 16

Provide another well documented example of vicariance involving the formation of the Isthmus of Panama

Answer 16

resulted in the evolution of related species pairs on the Atlantic and Pacific sides

Question 17

From an ecological perspective, what is an island?

Answer 17

any kind of isolated area surrounded by unsuitable habitat

Question 18

What is the species-area curve, and what does it describe?

Answer 18

relationship between habitat area and species richness is called the species-area curve

Question 19

What does a comparison of species-area curve for islands and comparable pieces of mainland reveal about species richness and the slope of a curve relating number of species to area? Why?

Answer 19

Islands usually contain fewer species
* That is, they have a lower value for the intercept on the S-axis of the species-area graph
* This is especially true for species occupying higher trophic levels Island Biogeography

(2) The species-area relationships for islands are on average steeper than those for mainland areas, that is, the slope of the line relating number of species to area is steeper
* These observations raise some intriguing questions, and we shall return later to consider some possible reasons for them!

Question 20

Describe the habitat diversity theory for explaining patterns of island biogeography and some of the factors it fails to consider.

Answer 20

Probably the most obvious reason larger islands contain more species is that they typically have more diverse habitat types

Question 21

What factors determine the number of species found on an island?

Answer 21

dynamic balance between immigration and extinction

Question 22

At what point does the colonization curve fall to zero?

Answer 22

eventually all species from the “species
pool” (potential colonizers from source areas
surrounding the island) will reach the island and
the immigration rate will drop to zero!

Question 23

Why should rates of extinction on islands increase as species richness increases?

Answer 23

competitive exclusion

Question 24

Why does the theory predict a dynamic equilibrium and what does this mean?

Answer 24

when the rate of immigration equals the
rate of extinction, a dynamic equilibrium of
species richness is reached

Question 25

What factors determine the shape of the immigration and extinction curves?

Answer 25

immigration and extinction

curves determines the actual equilibrium point

Question 26

What types of islands does the model predict will have the fewest number of species?

Answer 26

with decreasing
island size since smaller islands present
smaller “targets” for colonizers

Question 27

Give two reasons why smaller islands are likely to have fewer species than larger ones

Answer 27

higher for smaller
islands because of increased competitive
exclusion and smaller population sizes

Question 28

What is meant by the indeterminacy of island communities?

Answer 28

because there is a significant degree of
chance regarding exactly which species are
present in the community, this produces an
indeterminacy in species structure!

Question 29

Why do island communities often show patterns of disharmony in their species assemblages and what are the effects of such disharmony?

Answer 29

partially because of differences in powers of dispersal * Even within a taxonomic group, powers of dispersal can vary

Question 30

According evolutionary theory, how might rates of speciation on remote islands compare with rates of colonization?

Answer 30

consider the events which shape island communities over evolutionary time
* On oceanic (remote) islands, rates of speciation may be comparable with or even faster than rates of colonization!

Question 31

Why do islands often show high degrees of species endemism?

Answer 31

high degree of endemism (the occurrence of species found nowhere else) on islands reflects the influence of evolution in these isolated communities

Question 32

According to evolutionary theory, why might some remote island communities not be “saturated”?

Answer 32

imply because there has been insufficient time for the evolution of all of the potential species!

Question 33

Describe the SLOSS debate and how might be important to the design of wildlife refuges

Answer 33

many small islands may support more species than a comparable area of one or a few large islands

Question 34

What are riparian corridors and what is their importance to wildlife conservation?

Answer 34

not only provide such immigration routes for some species
* But they are also some of the most biologically diverse terrestrial habitats!