Patterns in biodiversity and their explanation Flashcards
What is biodiversity?
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
What are patterns in biodiversity?
-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
What is community ecology
Is concerned with the factors driving patterns of biodiversity
What is species richness?
Number of resident species
What is species heterogeneity/evenness?
Accounts for relative abundance of species as well as species number
When does heterogeneity increase?
When there are more species and when they are more equally abundant
(Shannon-Weiner Index)
What is alpha diversity?
Within area diversity
What is beta diversity?
Between area diversity, number of species present in area a and not in area b
What is gamma diversity?
Overall diversity across all areas within a region
What considerations with sample size need to taken?
If sample size is small, rare species are less likely to be detected
What habitats have less biodiveristy?
Alpine and Polar habitats
How many species of breeding birds were noted in Colombia?
1,525
How many breeding birds were noted in Greenland?
56
How many ant species were recorded in Brazil?
222
How many ant species were recorded in Arctic Alaska?
3
What are some generalities of the latitudinal diversity gradient?
-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
What are six factors thought to drive latitudinal diversity?
-Evolutionary speed
-Geographic area
-Interspecific interactions
-Ambient energy
-Productivity
-Disturbance
Describe evolutionary speed
-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
Describe geographic area
-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
Describe interspecific interactions
-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
Describe ambient energy
-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
Describe productivity
-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
What is some evidence of climatic drivers of diversity trends in marine bacteria (Fuhrman et al 2008)
-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
Describe disturbance
Moderate levels of ecological disturbance prevent some species from becoming competitively dominant and outcompeting other species