Lecture 7: Hyperdiversity Flashcards
simplest measure of species diversity/biodiversity:
species numbers
tropical forests are ___diverse
hyperdiverse
-rainforests are estimated to be home to__ % of all terrestrial species, despite covering __% of surface
50
<2
can be __ specie sin just 5 ha of forest
500+
AMAZON hyper diversity: estimated to be ___ trees
3.9X10^11
AMAZON hyper diversity: ___ tree species
~16 000
AMAZON hyper diversity: __ ‘hyperdominant’ tree species
227 –> represent ~50% of all trees
worlds most abundant tree
Euterpe precatoria 5.21 X10^9
second Protium altissimum 5.21X10^9
native tree diversity in the amazon is __X higher than in the GB & Ireland
30 times
Tropical forests are not the only hyper diverse systems, some other examples:
- coral reefs
- desert plants
- phytoplankton
- sewage
diversity relates to the number of
species in a given environment
current concepts of diversity are more complex than just the number of species present in a place, takes into consideration:
- species diversity
- functional diversity
- phylogenetic diversity
species diversity and tropical forests:
they are exceptional,
functional diversity is underpinned by
species and phylogenetic diversity
functional diversity:
refers to those components of biodiversity that influence how an ecosystem functions
key outcomes of functional diversity in tropical forests are:
- Productivity: tropical forests are the most productive ecosystems
- Carbon Storage: CS in tropical forests is a direct function of productivity
the relationship between FD and biodiversity has been ________: however …
controversial
however, usually positive and tropical forests are important with respect to all of these
zhang et al 2012 looked at
the drivers of productivity using a global survey of 54 sites
Cauvanaugh et al 2014 looked at
the relationship between carbon storage, environment and diversity
not only are forests significant carbon ___, but also this has been increasing:
diversity? amazon Above Ground Biomass has increased
–> reasons for increase include CO2 enrichment and successional changes
problem of diversity: Competitive exclusion:
- species that are similar to each other consume similar resources. hence compete with each other
- more similar species compete more strongly
- species that are too similar cannot coexist and one competitor is expected to outcompete the other
problem of diversity: limiting similarity
- competitive exclusion means that species that are too similar cannot coexist
- consequently there are limits to the similarity of species within ecological communities
- essentially room for one one species per niche
problems of diversity: not enough niches
- competitive exclusion and limiting similarity suggest that we need a niche for each species in a community
- BUT in hyper diverse communities there simply can’t be enough niches
- very limited set of required resources N,P,K water, light
ways in which species can divide niches: GAP DYNAMICS
- species may be adapted to exploit different stages of succession from gap opening to closing
- this generates diversity in species number and ecological strategies
theories of diversity:
large number of theories proposed to explain diversity and coexistence
- most theories are ecological (how spp co exist)
- some evolutionary (why do we have so many)
- difficult to evaluate
theories of diversity: 2 types
equilibrium & non-equilibrium
equilibrium theory:
balance between losses and gains to communities, such that overall species richness is maintained as a constant
- implies processes that balance diversity e.g. if species become rare then they should increase
- mathematically difficult
non-equilibrium theory:
disturbance (hurricane,fire etc) / stochastic (random) events prevent equilibrium being reached
-hence competitive exclusion DELAYED
intermediate disturbance hypothesis:
relationship between spp. diversity and level of distribution (normal distribution)
evidence that disturbance and diversity are related:
- However disturbance only slows deterministic extinction
- unless something else is going on
- e.g. adaptation to different environments
- trade-offs between competition and dispersal
- Adaptation to gap dynamics fits with evidence that disturbance promotes diversity.
age of tropical forests:
- evidence of amazon rainforest in SA dating back to at least the late Cretaceous-Eocene
- evidence rainforest have withstood severe environmental disturbance (e.g. glaciation)
- age and robustness should promote diversity
