Lecture 6 - hyperdiversity

Question 1

what is the simplest measure of a species diversity/ biodiversity but what is the problem with it?

Answer 1

species numbers e.g. species count - tells us nothing about interactions and roles in ecosystem/community

Question 2

describe tropical forests diversity

Answer 2

hyperdiverse - lots of species per hectare

Question 3

what are the problems of hyperdiversity?

Answer 3

1) why do we have such exceptional hyperdiversity?

2) unusual compared with similar systems

Question 4

describe the pattern of tree diversity in the Amazon?

Answer 4

• the amazon is the biggest ecosystem on the planet in terms of trees
• home to lot of rare tree species
• 227 ‘hyperdominant’ tree species represent 50% of all trees in the Amazon
• 62% of all species are expected to have populations under a million individuals and are equivalent to 0.12% of all trees in the Amazon

Question 5

what are the two must abundant tree species?

Answer 5

1) Euterpe precatoria
2) Protium altissimum
- both pioneer species - interesting what this tells us about the type of species that drive abundance

Question 6

describe native tree diversity in the Amazon

Answer 6

30x higher than in GB and Ireland (temperate forests)

Question 7

4 examples of other hyperdiverse systems

Answer 7

1) coral reefs
2) desert plants
3) phytoplankton
4) sewage

Question 8

what do modern definitions of species diversity incorporate?

Answer 8

functional diversity and phylogenetic diversity - they offer different perspectives on the diversity measure
- expected to be a relationship between the 2 e.g. more species means more output and more phylogenetic diversity means more different species which means more functions

Question 9

what is functional diversity?

Answer 9

• represents the sum of the roles that species perform in the community - most important
• refers to those components of biodiversity that influence how an ecosystem functions

Question 10

what are the 2 key outcomes of functional diversity in tropical forests?

Answer 10

1) productivity - rate (tropical forests are the most productive systems)
2) carbon storage - amount (direct function of productivity)

Question 11

what underpins productivity and what drives it ?

Answer 11

underpins = species richness and community composition

- functional traits of species within a community are important in driving productivity

Question 12

what is more important that diversity itself?

Answer 12

evenness - not enough to have lots of species in a community, the distribution of their abundances is also important

Question 13

what are functional traits?

Answer 13

how species grow - strategies for survival e.g. shade tolerance - richness, evenness and shade tolerance are not independent of each other - as you increase richness, evenness and phylogenetic diversity of the community you increase the trait diversity and hence productivity

Question 14

relationship between diversity and carbon storage

Answer 14

increasing phylogenetic diversity (genus richness) carbon storage increases - increase above ground biomass
- this phylogenetic diversity is important in addition to functional diversity

Question 15

what are the 3 problems of diversity

Answer 15

1) competitive exclusion - species similar to each other competing for resources - species too similar cannot coexist
2) limiting similarity - due to competitive exclusion there are limits to the similarity of species within ecological communities - only room for 1 species per niche
3) not enough niches - in hyperdiverse communities there simply cant be enough niches - limited set of required resources

Question 16

describe a way in which species can divide niches

Answer 16

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

Question 17

what are the 2 theories of diversity?

Answer 17

1) equilibrium theory - overall species richness is maintained as a constant by a balance in losses and gains - implies processes that balance diversity i.e if species become rare then they should increase
2) non-equilibrium theory - disturbance/stochastic events prevent equilibrium being reached - competitive exclusion delayed

Question 18

what are problems with theories of diversity

Answer 18

• most theories are ecological i.e explain how species can coexist - fewer are evolutionary i.e. why do we have so many species
• difficult to evaluate - time and spatial scales are huge and data is difficult to obtain

Question 19

what is the intermediate disturbance hypothesis

Answer 19

• species diversity in communities relies on disturbance - too much or too little aren’t good - middle allows maximum diversity
• disturbance delays competitive exclusion but doesn’t prevent it

Question 20

describe the significance of disturbance

Answer 20

• disturbance doesn’t explain hyper-diversity but does play a role in it
• any theory about diversity must incorporate disturbance

Question 21

why is is the Amazon so impressive ?

Answer 21

• evidence that the Amazon rainforest dates back to atleast the late Cretaceous
• evidence that rainforests have withstood severe environmental disturbances

Question 22

what is significant about the age and robustness of rainforests

Answer 22

• should promotes diversity - some evidence that this is the case but not universally supported
• diversification rates are higher in tropical forests

Question 23

what is evidence that disturbance and diversity are related?

Answer 23

• disturbance only shows deterministic extinction- unless something else is going on (e.g. adaption to different environments)
• trade offs between competition and dispersal
• adaption to gap dynamics fits with evidence that disturbance promotes diversity