Flashcards in Biodiversity and ecosystems Deck (20)
Define biological diversity?
The variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.
Define taxonomic diversity?
The number and relative abundance of taxa, defined by a hierarchical, evolutionary classification
Define phylogenetic diversity?
Relationships among taxa based on elapsed time since divergence (e.g. sum of branch lengths linking species in a phylogeny)
Define genetic diversity?
Nucleotide, allelic, chromosomal, genotypic or other aspects of genomic variability.
Define functional diversity?
Variation in the degree of expression of multiple functional traits.
Difference between ecosystem processes and services?
Processes are the flow of energy through the system.
Ecosystem processes such as forest primary productivity support beneficial ecosystem services by providing timber and regulating climate. Grouped into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and oxygen production; and cultural, such as spiritual and recreational benefits.
What happens when biodiversity is lost?
Reduces the efficiency by which ecological communities capture resources, produce biomass, decompose and recycle nutrients.
Impact is nonlinear and saturating, such that change accelerates as biodiversity loss increases.
Why are diverse communities more productive?
They contain key species that have a large influence on productivity, and differences in functional traits among organisms that increase total resource capture.
Maintaining multiple ecosystem processes requires higher levels of biodiversity than does a single process.
Effect of loss of diversity across trophic levels?
Has the potential to influence ecosystem functions even more strongly than diversity loss within trophic levels.
Different measures of stability?
What can you measure the stability of?
Fluctuations of individual populations.
Diversity and composition of whole communities.
Ecosystem process rates.
What is stability resistance?
For a given perturbation, systems that change less are more resistant. Change in biomass.
What is stability resilience?
For a given perturbation, systems with a faster rate of return to the equilibrium state are more resilient. Gradient of change in biomass.
What determines the long term overall temporal stability of the system?
Both stability resistance and resilience.
How does diversity affect stability?
More complex ecosystems have more routes of energy flow so that if a species is lost it is less likely that the remaining species lose their access to resources.
Diverse systems are more stable.
Paradigm reversal in community stability?
1970s - Robert May suggested that more diverse communities are less stable.
Showed that individual populations become less stable with:
-increased community species richness
-more links between species
-interactions between species are stronger
Perturbations are likely to propagate further in food webs with more species or a greater connectivity.
What is the portfolio effect?
Analogy to financial markets where a diverse portfolio of investments is more stable in the long term due to statistical averaging.
What is the insurance hypothesis?
Biodiversity provides an insurance against perturbations so long as the species respond in different ways buffering the ecosystem level process rates.
What makes total biomass production more stable over time?
When species populations fluctuate asynchronously.
Diverse communities have less stable individual populations but asynchrony fills in the gaps over time, stabilising the ecosystem productivity.
Less diverse communities have more stable individual populations but less stable prductivity overall.