3: LDG Flashcards
What do we mean by ‘diversity’ in LDG?
Usually shorthand for alpha diversity = number of species found in a location
define beta diversity
turnover in species i.e change in composition between two locations/ at the same location over time
Define gamma diversity
Number of species at a landscape scale i.e continental scale
Give an example of an exeption to the LDG
Gymnosperm (e.g pines, conifers) diversity peaks not at the equator but at Tropic of Cancer, smaller peak Tropic of Capricorn
LDG still supported as exceptions more likely to arise when considering finer taxonomic scale
Describe Hillebrand (2004) meta analysis on LDG
= analysis supported high generality of LDG
= concluded that there’s a variation in form of this relationship (e.g slope of line)
- Stronger with larger bodied organism, and trophic level
- Also varied in strength based on habitat type e.g weaker in freshwater than marine/terrestrial
Fundamentally, what is the no. of species a balance between?
Speciation (birth of new species) VS extinction (death of species)
Net diversification = speciation - extinction
Immigration (arrival of new species) VS emigration (species leaves area)
Net migration = immigration - emigration
What are the 3 groups of hypotheses for the LDG?
Chance events
Ecological factors e.g energy/productivity
Evolutionary/historical factors
Describe how land availability could explain the LDG
if species are distributed randomly through space you expect more species in locations with more land
Describe the mid-domain model
- If species ranges are randomly distributed across region, expect increasing overlap of species ranges (more species) towards the centre of the region
- Limited evidence
Define Actual evapotranspiration (AET)
Measures amount of water evaporated from land surface, combined with the amount transpired by plants
- Measure of energy availability (combines heat and water)
- Good proxy for plant productivity & ‘energy’ available for consumers
Describe the more individuals hypothesis (species-energy relationships)
More energy increases species pop. size, less likely to go extinct thus increasing total no. of species present at one time
Describe the chance hypothesis (species-energy relationships)
more energy in a given area allows more individuals to occur, increases no. of species by chance
Describe the more trophic levels hypothesis (species-energy relationship)
More energy enables pop.s to recover faster from disturbance thus reducing extinction risk
Describe the niche position hypothesis (species-energy relationships)
- Increased productive energy increases abundance of rare resources that are exploited by specialist niches
- In high-energy areas more species of niche specialists can maintain stable pop. sizes = increasing species richness
Describe the niche breadth hypothesis (species-energy relationships)
More energy increases abundance of individual resource types, enabling species to switch patterns away from less preferred resources
Reduced niche breadth = reduced niche overlap, reducing rates of competitive exclusion and thus elevating species richness in high energy areas
