Revision Lecture

Question 1

Latitudinal gradients

Species diversity decreases with…

Answer 1

Increasing latitude.

Question 2

What is the most common pattern found in graphs displaying endemic species richness vs altitude?

Answer 2

Hump shaped pattern.

Question 3

What are the 3 fundamental processes in biogeography?

Answer 3

1. Species: evolutionary process by which reproductively isolated biological populations evolve to become distinct species.
2. Extinction
3. Dispersal: the movement of organisms away from their point of origin.

Question 4

What are the 3 types of dispersal?

Answer 4

1. Jump dispersal (or long distance dispersal: dispersal that is accomplished by movement of individuals within a relatively short period.
2. Diffusion: a form of range expansion that is accomplished over generations by individuals spreading out from the margins of the species range.
3. Secular migration: geographic range expansion which is so slow (e.g many generations) that it is often accompanied by substantial evolutionary changes in the population en route. They expand to colonise new regions. Similar to diffusion.

Question 5

What are the two types of mechanism of movement?

Answer 5

Active: movement of an organism from one location to another by its own means.

Passive: movement of an organism from one place to another by means of a stronger force, such as water flow, wind or another organism.

Question 6

Types of barriers and dispersal routes:

According to Simpson…

Answer 6

1) Corridors
2) Filters
3) Sweepstake routes

Question 7

What is vicariance?

Answer 7

Attempts to reconstruct the historical events that led to observed distributional patterns based largely on the assumption that these patterns resulted from the splitting (vicariance) of areas and not long distance dispersal.

Geographical range of a taxa is split into parts by the formation of a barrier- no dispersal!

Geological/ climatic events

Question 8

Vicariance vs dispersal

Answer 8

1) Vicariance: species existed- then were separated and underwent allopatric speciation.
2) Dispersal: species disperses across an existing barrier- e.g islands already exist- some individuals made it to the next island, underwent allopatric speciation.

Question 9

What is macroevolution?

Answer 9

Changes in species (extinction and speciation).

Question 10

What is adaptive radiation?

Answer 10

A particular form of speciation where a single ancestor’s descendent species occupy a range of free niches (islands, after mass extinctions).

Question 11

What is allopatric speciation?

Answer 11

The result of geographic (spatial separation) followed by genetic differentiation in isolation until populations are so different they form different species.

Question 12

What is sympatric speciation?

Answer 12

Results from a physiological or behavioural change that isolates populations from breeding, such as switch in pollinators, or change in the time of breeding.

Question 13

Genetic drift vs natural selection

Answer 13

Natural selection is the most important way that evolution can take place- but it’s not the only way.

Another important mechanism of evolution is that of genetic drift, when random events eliminate genes from a population.

Two important examples of genetic drift are founder events and the bottleneck effect.

Question 14

What is genetic drift?

Answer 14

Change in allele frequencies (genes) in a population due to chance event.

More likely to occur in a small population (islands).

Unlike natural selection (favours beneficial traits) genetic drift is random. Can cause an increase of: beneficial, detrimental, or neutral traits.

Question 15

MacArthur and Wilson’s theory embraces two very general and long-known patterns in Island Biogeography:

Answer 15

1) Number of species to increase with island area.

2) Number of species to decrease with island isolation.

Question 16

The equilibrium theory of island biogeography in a nutshell

Answer 16

Species richness on an island represents a dynamic equilibrium controlled by the rate of immigration of new species and the rate of extinction of previously established species.

Question 17

What are the assumptions with the equilibrium theory of island biogeography?

Answer 17

1) Extinction is only influenced by island size.
2) Immigration is only influenced by island isolation.
3) Continued turnover occurs.

Question 18

What are baselines (or reference conditions)?

Answer 18

These are frequently derived from historical literature or from paleo ecological studies based on biological proxy, fossil or sub-fossil evidence (Willis et al 2010, Gillson et al, 2011).

Question 19

What is a species’ distribution model?

Answer 19

1) Models that predict distributions of species by combining known occurrence records with digital layers of environmental variables.
2) The most common strategy for estimating the actual or potential geographic distribution of a species is to characterise, the environmental conditions that are suitable for the species, and to then identify where suitable environments are distributed in space (Guisan and Thuiller, 2005).