Patterns in biodiversity and their explanation

Question 1

What is biodiversity?

Answer 1

The variety of life at all levels of organization (genetic variation within a species, the variety of species comprising a community and variability of communities within ecosystems

Question 2

What are patterns in biodiversity?

Answer 2

-Animal and plant life more varied in tropics than other parts of the globe
-Diversity decreases with increasing altitude
-Small remote islands have fewer specie than larger islands close to continents

Question 3

What is community ecology

Answer 3

Is concerned with the factors driving patterns of biodiversity

Question 4

What is species richness?

Answer 4

Number of resident species

Question 5

What is species heterogeneity/evenness?

Answer 5

Accounts for relative abundance of species as well as species number

Question 6

When does heterogeneity increase?

Answer 6

When there are more species and when they are more equally abundant
(Shannon-Weiner Index)

Question 7

What is alpha diversity?

Answer 7

Within area diversity

Question 8

What is beta diversity?

Answer 8

Between area diversity, number of species present in area a and not in area b

Question 9

What is gamma diversity?

Answer 9

Overall diversity across all areas within a region

Question 10

What considerations with sample size need to taken?

Answer 10

If sample size is small, rare species are less likely to be detected

Question 11

What habitats have less biodiveristy?

Answer 11

Alpine and Polar habitats

Question 12

How many species of breeding birds were noted in Colombia?

Answer 12

1,525

Question 13

How many breeding birds were noted in Greenland?

Answer 13

56

Question 14

How many ant species were recorded in Brazil?

Answer 14

222

Question 15

How many ant species were recorded in Arctic Alaska?

Answer 15

3

Question 16

What are some generalities of the latitudinal diversity gradient?

Answer 16

-Latitude ranges from 10 -90 degrees
-Latitudinal diversity gradient is a ubiquitous phenomenon
-Stronger gradients observed at regional scales compared to local scales
-Strength of relationship increases with body mass and trophic level

Question 17

What are six factors thought to drive latitudinal diversity?

Answer 17

-Evolutionary speed
-Geographic area
-Interspecific interactions
-Ambient energy
-Productivity
-Disturbance

Question 18

Describe evolutionary speed

Answer 18

-Faster rates of species evolution and diversification in tropical environments because of higher ambient temperatures, mutation rates, shorter generation time and/or faster physiological
-At higher latitudes there has been insufficient time for species to colonise or recolonise areas because of historical events like glaciations
-Difficult to test, relies on fossil record

Question 19

Describe geographic area

Answer 19

-Larger areas support more species than smaller areas; greater land area in tropics
-More complex habitats contain greater number of niches and support more species
-Can explain diversity gradients in some terrestrial systems but not marine systems

Question 20

Describe interspecific interactions

Answer 20

-Greater interspecific competition in the tropics - smaller niches
-Competing hypothesis: greater predation pressure in the tropics mean that prey population abundance stays low, thus reducing competition
-Competition may be important for parasites and predators
-Predation and disease may be more important among herbivores and plants

Question 21

Describe ambient energy

Answer 21

-More stable climate conditions in tropics allow more specialized species to evolve, more species are supported by a unit of habitat
-Conditions in low diversity habitats tend to be severe and/or unpredictable, species can not be as specialised
-Increased solar radiation in tropics= more energy available
-Supported by driver of trends in biodiversity over large spatial scales

Question 22

Describe productivity

Answer 22

-Diversity proposed to increase with productivity
-Longer growing season in tropics- primary producers are temporally partitioned (complete their main growth period at different times)
-More species can co-exist

Question 23

What is some evidence of climatic drivers of diversity trends in marine bacteria (Fuhrman et al 2008)

Answer 23

-Used genetic techniques to measure species richness in 103 near-surface samples of marine bacterial plankton from tropical to polar sites in both hemispheres.
-Reported significant latitudinal gradient in richness
-Diversity was correlated with temperature

Question 24

Describe disturbance

Answer 24

Moderate levels of ecological disturbance prevent some species from becoming competitively dominant and outcompeting other species

Question 25

Describe ecological disturbances

Answer 25

-Communities are rarely stable over long periods of time
-Biotic disturbances (disease, predation)
-Abiotic (fire, storms, floods)
-Vary in scale, frequency and intensity
-Communities will tend to recover towards the climax stat through natural succession

Question 26

List the timeline of a disturbance event

Answer 26

-Disturbance
-Succession
-Recovery

Question 27

What is the intermediate disturbance hypothesis?

Answer 27

-Moderate frequency and intensity can increase biodiversity
-The community is dominated by the few species that are tolerant of disturbance (Giant sequoias using fire to reproduce)
-With infrequent and low intensity disturbances, community is dominated by species that are effective at eliminating competitors

Question 28

Summary of disturbance hypothesis

Answer 28

-Low levels of disturbance allow competition to reduce diversity
-Predicts that species diversity will be highest at intermediate levels of disturbance
-High levels of disturbance reduce diversity
-Supported by laboratory and field studies across terrestrial, marine and freshwater systems
-Difficult to consistently quantify disturbance across studies

Question 29

Why are biodiversity trends important?

Answer 29

-Global biodiversity is currently declining at an alarming rate
-Driven by human activities (pollution/overfishing/climate change)
-Understanding what drives variation in biodiversity and what promotes high biodiversity in some areas can inform the conservation of biodiversity