Community diversity is correlated with primary productivity—
The tropics are more productive—
- could be that they get more energy
- could be that they’re more species rich
Our bodies have different communities of bacteria.
Questions for community ecologists
- Which concepts
o niche concept
o Shannon diversity
- processes responsible for the patterns we see
o competition, predation, dispersal
- why we have these species and not some other species?
- why do we have the richness we do?
- how stable is it / robust to perturbation?
- is one species more important than others in dictating the community’s composition?
The Niche Concept
- ex. Habitat: biology department; Niche: what classes he teaches, etc.
- Niche—what a species does within its community
- Hutchinsonin sense—sunlight vs temperature vs nutrients space
- Niches can overlap
- The more overlapping in the niches = the more competition between them; less likely to
keep both in the community
- things evolutionarily diverge to minimize their overlap in niche space
- if you introduce a species with the same niche, the first species will evolve a lot faster in
order to carve a more unique niche space—these are genetic changes!
Competition begets evolution of increased phenotypic distance between competitors, causes
niche space to be “explored” evolutionarily, and leads to species diversity, phenotypic diversity,
Short version: Competition diversity!
There are other forces that also do things like this—will cover later.
Fundamental niche—what abiotic forces will permit
Realized niche—what the biotic and biotic forces will permit—competition, predation—
predation will shrink the realized niche relative to the fundamental niche
Going back to diversity
- Shannon diversity index gives an H
- Raise e to the power of H—get A
- Assume A equally abundant species, that’s equal to an H - Higher H = most even
Thinking about two species and the relationship between them is more population ecology + one
other species, not really commu