Biodiversity Measurements
Diversity (species richness)
- The most common, see Community Ecology
Range size
- Range size estimation done using minimum convex hull of observevations
- This could often be an overestimation when disjunct populations exist
- Most species have a very narrow distribution
Explanations for range size
Table showing different factors determining range size
!Macroecology_partII_2026, p.57
- Species at higher latitudes tend to have larger range sizes (Rapoport's rule)
- However, with birds, this only applies to the northern hemisphere: this is probably because of large land areas inthe northern hemisphere. So this doesn't apply to all clades
Body size trends
Bergmann's Rule:
Body size increases along decreasing temperature gradient for endothermic species (mammals and birds)
- The strength of the rule depends on the clade
Foster's Rule(AKA Island rule)
Larger animals will be smaller and smaller animals will be larger compared to their mainland counterparts.
- Island dwarfism/gigantism
- Thought to reflect food availability, predation pressure and or cometition
- Systematic review of data found widespread support for this rule
Other body size rules:
| Name | Def |
|---|---|
| Allen's Rule | Animals have smaller tails, ears and limbs in cold climates to reduce heat loss |
| Bogert's rule | Pigmentation is more intense in cold climates, since darker colors absorb more radiation |
| Gloger's rule | Pigmenation is more intense in the tropics in endotherms, due to increased production of melanin |
| Harrison's rule | Host and parasite body sizes covary positively (larger hosts provide more resources) |
| Hesse's rule | Endothermic animals in cold or high-altitude environments have larger hearts w.r.t. body weight |
| Jordan's rule | Number of meristic characteristics (countable structures, Evo-Devo#Modularity) of fish increas in colder waters due to longer development |
| Murphy's Rule | Palearctic endotherms (birds and mammals) are larger in seasonal environments iwth greater temperature range - larger animals are more resistant to food scarcity (does not apply to N. America) |
| Thorson - Rass' Rule | Reproductive strategy of larger offpsring sizes in smaller numbers is favored towards the poles in marine organisms |
- Bogert's Rule and Gloger's rule oppose each other
- Murphy's rule and Bergmann's rule resemble each other, but Murphy's is more related to seasonality
- You may find these rules referencesd when reviewing macroecology literature: certain studies will support Gloger's or Bogert's rule for example
- Human languages also show ecological rules
- Review of ecological rules: Shelomi and Meiri 2023
Abundance distributions
- Distribution of abundances of all species within an ecological community - a theoretical foundation for exploring other ecological patterns
- Species Abundance Distributions (SADs). There are 30-40 proposed SAD models
- Most comon is the log-normal and logseries modesls
- Most can be described by these distributions, but not all.
Sampling effort
And of course this is affected by sampling effort.
- Well-sampled communities are more bell-shaped, while less well sampled might show more of a skewed SAD distribution
Differences in SAD distributions?
- Shape of SAD also depends on:
- Biome, speciation rate, migration rate from meta-community
- spatial/temporal scale of sample
- How the niches within the samples are separated from each other (niche paritioning)
- Disturbances affect community structure: polluted communities may be dominated by a few tolerant species
Importance of SADs
- Being able to explain unevenness in communities helps us make strongstatements about which mechanisms structure communities
- Used to give clear definitinos to rare and common species for conservation
Range size and abundance link
- Locally abundant species tend to be widespread, locally rare species tend to be narrowly distributed
- "Abundant-center" hypothesis - species sampled closer to the edge of its range will be less abundant there:
!Macroecology_partII_2026, p.86