PCE - 11 Flashcards
what are examples of macroecology?
SARs, islands biogeography and latitudinal gradients
what are the goals of macroecology?
- To identify general emergent patterns in ecological systems
- General processes/mechanisms reflected in ‘emergent’
patterns in statistical distributions of individuals, populations and species - To test for repeatability of patterns in statistical distributions to infer the presence of ‘law-like’ ecological processes
what were Alexander von humboldts observations of varying latitudes and what did he hypothesise?
many more species at low latitudes and he hypohtesised that temperature was the cause
how can you map global richness?
by dividing the world into equal areas and measure richness
what are the 2 main categories of hypotheses for ‘what determines variation in the number of species in a community at a global scale?’
1) climatic/ environmental factors (ecology)
2) historical factors (evolution)
what 2 things can climatic factors affect?
1) energy / productivity of an area
2) spatial and habitat heterogenity (diversity)
what is PET?
potential evapotranspiration - amount of water that would evaporate or be transpired from a saturated surface - primitive measure of available energy or productivity
describe energy/ productivity patterns?
as energy increases = faster growth rates and larger populations, narrower ranged species can co-exsist
what does habitat heterogeneity reflect?
- a resource axis and the extent of potential niches
- allows for more species with small niches to co-occur
what are the 2 things that can determine the number of species that can co-exist
1) climate
2) environment
how do you work out net diversification?
speciation rate - extinction rate
describe the tropical cradles model
- the tropics are home to young, rapidly speciating lineages
- speciation rate peaks in the tropics
- extinction rate invariant with latitude
describe the tropical museums model
- home to old relictual species
- speciation rate invariant
- extinction rate declines in the tropics
what are the 3 historical processes (evolution)?
1) tropical cradles of diversity
2) tropical museums of diversity
3) out of the tropics
describe the out of the tropics model?
- species form in the tropics and move to extratropics
- speciation rate peaks in the tropics
- extinction rate declines in the tropics
what are ecogeographical rules?
variation in the traits of organisms over geographical or environmental gradients
what were bergmanns rule hypotheses?
he proposed that large body size is advantageous at high latitudes due to it reducing heat loss from a lower surface area to volume ratio
after many tests what were the conclusions of bergmanns rule?
a common pattern driven by multiple processes:
- thermoregulation (intra and interspecific)
- taxonomic turnover (interspecific) - how many taxa are alive at the time
- community assembly (interspecific) - the identity and abundance of species within a community
what did Allen observe?
he observed that the length of appendages in closely related endothermic vertebrates increased in hotter environments
what was Allens hypothesis?
thermoregulation - shorter appendages conserve heat and longer appendages are more effective in dissipating heat
what were the conclusions to allens rule on pattern?
- strong support for his rule
- data support both pattern and process
why are marine ecogeographical rules less well studied?
because marine data is harder to collect
what is jordans marine ecogeographical rule?
- number of vertebrae in marine fish increases towards higher latitude
- may be related to body size trend
- weak in migrant fish, stronger pattern in non-migrant species
what is Thorsons marine ecogeographical rule?
Dominant mode of development switches from
pelagic (larvae disperse with ocean current) in the tropics to direct development (no dispersal) at higher latitudes– direct developers more likely to become geographically isolated and speciate at high latitudes
what is Glogers ecogeographical rule?
pigmentation is darker in hot and humid zones (observation from birds)- few tests little support
with is rapoports rule?
the tendency for species ranges to become smaller at lower (tropical) latitudes- many tests, equivocal (questionable) support
what is the problem with Bergmans rule on latitude?
there is too much focus on latitude causing the differences in body size when actually the pattern is really about temperature
what were the conclusions to bergmanns rule after testing wether temperature had an effect on interspecific species?
temperature is the strongest predictor of body size within genera, families and order but not the only part of the picture
what genera have the widest overall temp range?
orders/families that occur at low temps
describe energy/ productivity patterns?
they are inconsistent - can show that productivity effects species richness but in some taxas it doesnt
