Community Assembly and Functional Diversity Flashcards
What is species composition?
Focuses on the identity of species within communities e.g. niches, traits and functions.
What is functional structure?
The distribution of species and their abundances within the overall niche space occupied by a community.
What is community assembly and what are the two timescales it operates over?
The order in which communities accumulate species and the combinations of species that can co-exist. Timescales include:
Ecological (short term) - immigration/extinction
Evolutionary (long term) - speciation/extinction
Why is it important to understand community assembly and structure?
How structure relates to ecological functions and processes
Strategies for community restoration after degradation
Community disassembly under human disturbance
Ecology of invasions by non-native species
What are some influences on community structure?
External influences:
- Regional pool effects
- Random immigration/neutral processes
- Habitat filtering and dispersal from regional pool (non-random)
Internal Dynamics:
- Density-dependent effects
- Inter-specific interactions
What is environmental filtering?
The non-selection of certain species that can’t exist due to certain abiotic/biotic conditions in the environment.
Results in the formation of communities with similar traits tending to co-occur more often that expected by chance.
Limiting similarity results in groups of species that have similar resource use tending not to co-occur at small scales.
How does competition affect community structure?
Past selection has favoured competition avoidance.
Gause’s principle - limiting similarity
Niche differentiation and morphological/functional differentiation
Saturated communities tend to be closer to equilibrium and will show more competition
What are null models?
Null model analysis is used to test whether differences in community structure are no more frequent than could occur by random combinations of species.
Doesn’t incorporate competition.
Probability of species being drawn is weighted against its abundance relative to the regional species pool. Hence, if there are 10 species in the pool:
(abundance of species x / mean abundance of all species) x (1/10)
