Revision Lecture Topics

Question 1

Latitudinal gradients

Answer 1

Species diversity decreases with increasing latitude.

Increasing species diversity from the poles to the Equator.

Question 2

Elevation pattern on graphs?

Answer 2

Hump-shaped pattern: described as the most common in a review of 304 data sets (Rahbek, 2005)

Question 3

What are the three fundamental processes in biogeography?

Answer 3

1. Speciation: 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 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) the is often accompanied by substantial evolutionary changes in the population en route. They expand to colonise new regions. Similar to diffusion.

Question 5

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

Barriers and dispersal routes

Answer 6

According to Simpson

1. Corridors
   Dispersal route that permits the movement of many (or most) species of a taxon from one region to another. No selectively discriminate against any form.
2. Filters
   Dispersal route that is more restrictive than a corridor. It selectively blocks the passage of certain forms while allowing those able to tolerate the conditions of the barrier to migrate freely.
3. Sweepstake routes
   A severe barrier that results in the partly stochastic (by chance) dispersal of some elements of a biota, and the establishment of a disharmonic biota.

Question 7

What is vicariance?

Answer 7

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

Question 8

Vicariance vs dispersal

Answer 8

Vicariance- species exist- then were separated and underwent allopatric speciation.

Dispersal: species disperse across an existing barrier- e.g islands already exist- some individuals made it to the next island and underwent allopatric speciation.

Question 9

What is genetic drift?

Answer 9

• Change in allele frequencies (genes) in a population due to chance event (random process). Non-influence of natural selection.
• More likely to occur in small population
• Unlike natural selection (favors beneficial traits) genetic drift is random. Can cause an increase of: beneficial, detrimental, or neutral traits.

Question 10

What is gene flow?

Answer 10

The transfer of genetic variation from one population to another.

Question 11

Types of genetic drift

Answer 11

Founder effect

Population bottleneck

Question 12

Founder effect

In the founder effect what does a small population size mean?

Answer 12

change in gene frequency due to colonization of a new area by a limited number of individuals.

It means this there is reduced genetic variation from the original population.

Question 13

Population bottleneck

Answer 13

change in gene frequency due to a drastic reduction in the size of the population.

For example, a natural disaster or as a result of fragmentation or overexploitation. When a population experience a large reduction in the number of individuals, the survivors carry only a fraction if the genetic diversity that was present in the original, larger population.

Question 14

What is speciation without physical separation?

Answer 14

Sympatric Speciation

Question 15

What is the mechanism of sympatric speciation?

Answer 15

When a population uses resources that are different from the original population.

Question 16

What is parapatric speciation?

Answer 16

Parapatric speciation is a mode of speciation in which differentiation occurs when two populations have contiguous but narrowly overlapping ranges, often representing two distinct habitats. An intermediate between allopatric and sympatric

Question 17

What is adaptive radiation?

Answer 17

It occurs when a single ancestor diverges into a host of species that use a variety of environments and that differ in traits used to exploit those environments.

Question 18

What is macroevolution?

Answer 18

Changes in species (extinction and speciation) are macroevolution.

Question 19

What is allopatric speciation?

Answer 19

The result of geographic (spatial separation) followed by genetic differentiation in isolation until populations are so different they form different species (1 species-> species). (Lomolino et al, 2010)

Question 20

What is sympatric speciation

Answer 20

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

Question 21

There are two modes of allopatric speciation:

Answer 21

1) Vicariance

2) Founder events

Question 22

What is vicariance allopatric speciation?

Answer 22

Environmental change can create a barrier to dispersal within a species range. Such events are called vicariant events.

Question 23

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

Answer 23

Number of species to increase with island area.

Number of species to decrease with island isolation

Question 24

Species richness on an island represents a dynamic equilibrium controlled by what…?

Answer 24

The rate of immigration of new species and the rate of extinction of previously established species.

Question 25

What are the main assumptions with MacArthur and Wilson’s theory?

Answer 25

Extinction is only influenced by island size

Immigration is only influenced by island isolation

Continued turnover occurs

Question 26

Define invasive species

Answer 26

Species that reproduce in large numbers and spread over a considerable area causing damage.

Question 27

Establishment of an invasive species requires…

Answer 27

dispersal across barriers, colonization, and successful reproduction.

Question 28

What are the generalised stages common to all species invasions?

Answer 28

Species pool
Entrainment 
Introduction 
Colonization
Establishment 
Spread
Integration

Question 29

The Cane Toad and the northern Australian fauna case study

Answer 29

Toads eat a lot – reduce population size of invertebrate prey?

Because they are toxic, they kill naïve PREDATORS – none of the Oz predators knew not to eat cane toads

Major problem for wildlife conservation

Public also concerned—topic of major public debate

Question 30

What is fragmentation?

Answer 30

Habitat fragmentation is the process by which habitat loss results in the division of large, continuous habitats into smaller, more isolated remnants (Fahrig 2003).

Also known as fragments or habitat islands.

Question 31

Where are baselines (or ‘reference’ conditions) frequently derived from?

Answer 31

From historical literature or from palaeoecological studies based on biological proxy, fossil or sub-fossil evidence (Willis et al 2010, Gillson et al, 2011).

Question 32

What is a species’ distribution model?

Answer 32

Models that predict distributions of species by combining known occurrence records with digital layers of environmental variables.

Question 33

The most common strategy for estimating the actual or potential geographic distribution of a species is to…

Answer 33

Characterize the environmental conditions that are suitable for the species, and to then identify where suitable environments are distributed in space (Guisan and Thuiller 2005).