MODULE 5 OVERVIEW Flashcards
What is an ecological community?
a group of potentially interacting species that occur together in space and time
What ecological processes affect communities?
- selection
- drift
- speciation (diversification)
- dispersal
What evolutionary processes affect population?
- selection
- genetic drift
- mutation
- gene flow
What traits?
things that drive their response to environment
What is selection?
changes in community structure caused by non-random (deterministic) fitness differences between taxa
sites vary with respect to temperature, rainfall, soil, fire regime
What are the features of selection pressures?
- vary across space / time
- constant
- density-dependent
What is diversification?
the evolution of new lineages from existing lineages
What is a metacommunity?
a group of local communities occupying a set of habitat patches that are linked by the dispersal of multiple, potentially interacting species
What are ecological processes?
processes that lead to changes in the species composition of a community
What are xeromorphic traits?
structural adaptations that reduce water loss
What are pyrophytic traits?
adaptations that allow plants to deal with fires
Which ecological processes help to explain the current diversification of Australian plant communities?
- persistence of rainforest species that evolved BEFORE the breakup of Gondwana
- persistence of species that evolved AFTER Gondwana breakup in response to a trend of drying of the continent and increased frequency of fire
- dispersal of rainforest species from SE Asia into Australia
What is alpha diversity?
the composition of a local ecological community with respect to its RICHNESS (number of species), EVENNESS (Distribution of abundances of the species), or both
What are some issues with describing ecological communities?
1) detectability of species
2) taxonomy (we don’t have a full description of ALL the species that are present)
We can measure species richness (sum of species present) but NOT species evenness because. . .
the abundance actually can’t be determined
The species range is a subset of. . .
the environmental range
Define niche
Ecological niche is a term for the position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role in the ecosystem.
What are 2 factors that influence distribution?
1) conditions e.g. light or temp
2) resources e.g. food
How did Hutchinson define niche (fundamental niche)?
a multidimensional hyperspace containing conditions & resources that allow the species to survive = fundamental niche
What is the realized niche?
smaller than the fundamental niche due to:
- COMPETITION
- DISPERSAL LIMITATIONS
- DISTURBANCES
- STOCHASTICITY (chance events)
What are some examples of environmental gradients?
- cover
- aspect
- solar radiation
- temp
What are some environmental variables for terrestrial settings?
- climate
- soil type
- humidity
What are some environmental variables for freshwater settings?
- temperature
- water quality
- flow magnitude & variability
What are some environmental variables for marine settings?
- depth
- temp
- salinity
- currents
- dissolved oxygen
What is competitive exclusion?
if 2 species compete for the same limited resource, one will dominate in the long term
What is resource partitioning?
species change morphology (shape + size) to reduce competition
- known as character displacement
Can resource partitioning occur through changes in behaviour?
YES
e.g. changing from nocturnal to diurnal
Give an example of how spatial / temporal variability allows co-existence
- different moisture levels across an area
- temp changes at dif times
How can community patterns be measured in space?
structure e.g. height of vegetation
env. relationships
Types of interspecific interactions
1) mutualism
2) competition for resources (-/-)
3) predation / parasitism
4) commensalism
What are tolerable parasites?
those that have evolved to ensure their own survival and reproduction but at the same time w minimum pain and cost to the host
What is commensalism?
where one species benefits and the other doesn’t really get affected (neutral outcome for them)
With trematodes, where does sexual reproduction happen?
in the definitive post
Features of parasites
- smaller than host
- live on/in host for extended period of time
- usually don’t kill host
Even though parasites are very small, they are often. . .
in such abundance that their total biomass is very significant within ecological communities
What is a keystone predator?
has such a important role in the community that it helps to define the community - if it is removed the community will be drastically different
e.g. sea starts who keep mussel levels in check in the community
Direct effects of predation
more animals alive or dead
Indirect effects of predation
prey learning to hide
may be in the form of developmental, morphological, physiological, or behavioural adaptations
What’s weird about indirect effects of predation?
even the presence of the predator can have important effects on populations and things, even if they aren’t actually doing any predation.
Like nothing needs to actually be eaten for there to be an effect from their presence (fear of predation)
What are trophic cascades?
predator-prey effects that alter the abundance, biomass, or productivity of a species, functional group or trophic level across more than one link in a food web
one predator-prey interaction that has big cascading effects across more than just the direct relationship
Examples of parasites
- protozoans
- animals
- fungi
- plants
Predation (e.g. indirect effects) on birds
SPATIAL arrangements – birds will nest far away from area of predators
What are the effects of grazing?
- change composition & structure
- increase cover
- increase exotic weeds
- decrease plant species richness
What is the topological food web?
focus on number & distribution of connections, using data
Distinguish b/w top-down and bottom-up control.
top down control: when predators have an effect on communities
bottom-up control: when producers have an effect on predators
Interspecific interactions are important across many different scales
1) time (first pollinating relationships millions of years ago)
2) space (the migration of Bogong moths and their predation by mountain pygmy possums)
3) body size (antarctic krill and their predator the humpback whale)
Mutualistic relationships are the result of. . .
coevolution, when unrelated organisms evolve in a coordinated fashion
Mutualistic relationships can be. . .
specific –> b/w 2 species
diffuse –> b/w groups of species
What is mycorrhizae?
fungus that grows in association with the roots of a plant in a symbiotic or only mildly pathogenic relationship
Explain fungal mycorrhizal networks
Fungal mycorrhizal network (generally in soil) provides water, vitamins, minerals and other nutrients to plants (their roots), and the plants give back photosynthetic products (sugars) to the funghi.
Things and information can also be passed (via biochemical signals) through this network to other plants.-
Plants are generally more resistant to pathogens when in these relationships
What are functional groups?
a group of species that perform a similar function in a community
Example of a functional group
corallivores feed on coral
excavators take large bites of living coral & the coral skeleton
What is succession?
natural changes in the composition and structure of an ecological community over time
- the replacement of one community by another
Succession can be. . .
Orderly - nice logical sequence up to optimal community
Not orderly - takeover domination of one particular tree type during colonisation when fire management regimes are out whack
What is a disturbance?
a discrete event that disrupts the structure of an ecological community, changing resource availability and/or the physical environment
Examples of natural disturbances
- bushfires
- floods
- cyclones
- volcanic activity
- disease
Examples of human-generated disturbances
- habitat clearing
- urban development
- pollution
What are some effects of disturbance?
- selection
- drift
- dispersal (some new species may move in)
What is a disturbance regime?
the long-term pattern of disturbances across a landscape - its frequency, size, & intensity
Disturbance regimes are estimated using. . .
historical data
Invasive species affect. . .
terrestrial
freshwater
marine communities
What are the pros of: conservation of single species
tangible target that is conceptually simple and can have charismatic draw for people’s efforts & engagement
good for support, funding, policy, awareness…
What are the cons of: conservation of single species
expensive, risky, & may mean conserving a species that has no viable (wild) habitat
Pros of conserving ecological communities
can target multiple species at once, with more efficient use of resources, & can support non-charismatic species
(more important for inter-species relationships)
Cons of conserving ecological communities
requires protection of land, & communities may be subject to multiple stressors and threats
may be at cost of humanitarian / economic benefits
What are some of the issues faced by the Coastal Banksia Woodland (an endangered ecological community)?
It faces a range of threats, habitat loss, and fragmentation (overdevelopment, agriculture, urbanization, clearing for mining) as well as introduced pathogens, invasive species, and climate change
Threatened ecological communities are recognized under the EPBC. Was it effective?
No! Species still declining, clearing of threatened ecological communities is rarely prevented
Ecological problems ALWAYS have. . .
interrelated social problems that must be considered
