Community Structure and Diversity Flashcards
Community
group of cooccurring, interacting species
Species Richness
the number of different species in a community
Species Evenness
relative abundances of species compared with one another
What does the Shannon index do?
quantifies the diversity of a community
What is the range of the Shannon Index?
0-4
What is refraction analysis used for?
used to make species accumulation curves, helps determine when most of the species in a community have been observed
What is the purpose of a Rank Abundance Curve?
give a snapshot of overall diversity in a community and can suggest what species interactions might be occurring within the community
Direct Interactions
A directly interacts with B (i.e. species A eats species B, species A allows species B to grow more abundantly…etc)
Indirect Interactions
A directly interacts with B which indirectly effects C (i.e. a plant (A) encourages plant (B) to grow. An insect (C) eats plant (B), so plant (A) has indirect interactions with the insect (C))
interaction webs
non trophic interactions, i.e. commensalism, competition
trophic webs
energy (trophic) interactions, i.e. food webs
what are keystone species?
Species with low abundance or a small size, but a large impact (ex: starfish)
How do you differentiate between a keystone species and a dominant species?
A dominant species in an ecosystem is the most abundant species present. It makes up the highest percentage of the total biomass in the system. A keystone species is one that has the greatest effect on all of the other species in an ecosystem.
are top predators always keystone species?
No- if the prey isn’t abundant, the predator isn’t a keystone species
What are ecosystem engineers?
What is their impact?
Any organism that creates, significantly modifies, maintains, or destroys a habitat. They can have a large impact on the species richness and the kinds of landscapes that are available to a community. (ex: beavers, worms, trees)
what is ecosystem redundancy?
When the functional contribution of additional species reaches a threshold because as more species are added to the community, there is overlap in their function
What is biogeography?
the study of patterns of species composition and diversity across geographic locations
What is the Cradle Hypothesis?
everything originated from low latitude ecosystems then moved North and South when disturbances were low enough
What is the typical pattern for species richness and latitude?
Low latitude = greater species richness
High latitude = less species richness
What hypotheses explain the pattern of species richness and latitude? (3)
- Species diversification rate is higher in the tropics
- Diversification rates are similar, but evolutionary time is greater in the tropics
- Higher productivity results in more abundant resources in the tropics
What different interactions among species can affect species richness in communities?
Resource partitioning is theorized to reduce competition and increase species diversity.
Disturbance, stress, predation, and positive interactions can mediate resource availability, thus promoting species diversity
What kinds of ‘filters’ determine which species are found in a community?
Regional species pool, dispersal ability, environmental conditions
What does the Regional Species Pool limit?
Regional species pool provides an upper limit on the number and types of species that can be present in a community
