EE Lecture 39: Global Diversity Patterns Flashcards
what diversity gradient do birds show
latitudinal diversity gradient
what evidence is there that the latitudinal diversity gradient hypothesis is correct
`for birds, number of species in tropics is far greater than N/S hemispheres
why are there more species in the tropics
tropics act as a cradle -> faster speciation
tropics act as a museum -> lower extinction, longer time
higher carrying capacity: more niches, larger niches
larger land surface area
how do the tropics act as a cradle
faster speciation
how do the tropics act as a museum
lower extinction
longer time
what is the result of the tropics having a higher carrying capacity
more niches
larger niches
what are the main hypotheses for global diversity patterns
area
energy
time for speciation
niche conservatism
discuss the area hypothesis for global diversity patterns
shown by SAR (species area relationships)
big tropical regoin, likely that theres more species there
SAR exlpains 7% of variation in flowering plant species richness
give an example of SAR relationships in flowering plants
SAR explains 7% variation in flowering plant species richness
300,000 sp of plants -> high species richness
what are the core predictors of species richness
potential evapotranspiratoin
number wet days per year
measurements of topographical and habitat heterogeneity
discuss the residual differences across the major floristic kingdoms
the residual differences across the major floristic kingdoms, after accounting for enviro effects are minor - with the exception of Cape Region (v. diverse)
discuss the species energy relationship hypothesis - what does it involve
energy in the form of potential evapotranspiration more energy (spesh@tropics) = more species as can accumlate more biomass therfore increased carrying capacity
what is the strongest single climate predictor
evapotranspiration
why in terms of energy/evapotranspiration are there more species at equator
direct insulation at equator - get 2.5 times more energy than at the poles - more concentrated therefore more energy converted into biomass
how much of the variation in plants is eplained by temperature and evpotranspiation
25%
what are the main places where mammalian species richness is high
where its warm,wet and mountainous
where N/S biomes join up
what causes the affect of SER (species energy relationship)
faster evoln - mutation rates, shorter lifespan, faster speciation
more biomass - high carrying capacity
what are the problems faced by trying to generalise global biodiversity patterns
the lack of fit of plant diversity compared with the model shows a spatial
pattern
clades differ in where they are in the world
what is the time for speciation hypothesis
glaciation wiped high latitudes clean
most tropical regions have been more stable
temperate speciation rates might now be high
what is the tropical niche conservatism hypothesis
tropics are easier to adapt to due to less seasonal variation
seasonality is difficult to overcome, so if you can, you can radiate
predict high temperature speciation rates
assumes adaptation t high latitude is difficult
molecular phylogenies of New World birds and mammals say temperate rates of speciation and extinction are higher
predict highrates of speciation in temperate clades and predicts temperature clades wll be nested within tropical clades
why are tropics easier to adapt to
due to less seasonal variatoin
what does the tropical niche conservatism hypothesis predict
high rates of speciatoin in temperate climates and that temperate clades will be nested within tropical clades
what do molecular phylogenies of New World birds and mammals show about temperate rates
there are far greater temperate rates of speciation and extinction in New World birds
what are the three main aspects of biodiversity
functional
structural
compositional
what was the traditional view of microbial biodiversit
organisms
how are microbes distributed
wind
rain
but the environment seleces
what seems to be a key determining factor for bacterial biogeography
pH - espesh in British soils - possibly due to latitudes
how are we discovering the true diversity of fungi/protists/proKs
by using environmental DNA sequencing
what are the main considerations of host associated microbes
species area
productivity
ph
oxygen levels
