Community ecology Flashcards
(18 cards)
Methods to assess biodiversity
Quadrats
Focal walks
Trapping eg camera traps
Benefits and limitations
Provides relative abundance of species
Some methods may be bias eg focal walks and the time of year as warmer weather could bring species out more
Labour intensive
Need specialist expertise
Molecular techniques
Collecting samples of DNA in pond water
PCR to amplify ‘barcoding’ genes present in a broad range of taxa
Sequence through NGS
Resolve species present by comparing to reference databases
Limitations of molecular techniques
Many microbes are unculturable
Only means of identifying is through DNA
Very broad sampling very quickly
Many have biases and some taxa have no representation
Not quantative
Can work better in some environments than others
Requires technology base and experience
What metrics summarise diversity?
Alpha - number of species in a site
Beta - variation between sites
Gamma - number of species in a landscape
Consumptive interactions
Consumptive is associated with energy transfer
Herbivory, predation, parasitism, decomposition
As described in food webs
Can be specialist or generalist, specialists eat one thing and generalists eat many
Parasites are commonly specialist
Specialists
Adapted to specific defences
Eg tolerance/detox of plant defensive chemicals eg coffee beans and caffeine
‘Lock and key’ parasites, receptor binding
Also dependent on the fate of prey
How to identify and measure consumptive interactions
Classical methods like watching and analysis of excretion
DNA based like barcoding analysis of gut contents
Non-consumptive interactions
Not involving energy change
Can be direct evolved interactions like symbioses and mutualisms
Protection, offence, anabolism, digestion, pollination
Can be a byproduct of activity
Non consumptive interactions - facilitation
Facilitation - where one species benefits another without causing any harm to itself
Coral as a substrate for all other reef species
Beavers damming activities result in flooded lands and slowed rives
Earth worms drainage and oxygenation of soil
Negative examples include habitat poisoning eg phenols and tannins in pine needles
This inhibits decomposition and plant growth
Indirect effects of non-consumptive interactions
What one species is doing may hinder another
It defines community biodiversity without consumption or direct action
Activities of an organism create or destroy the environment for others
Keystone species
One whose removal has an impact on community composition that exceeds its abundance (the species can be rare)
Two types - ecosystem engineers if habitat modification eg beavers
Ecologically dominant predators where removal leads to competitive dominance in the trophic level below
How to identify an ecologically dominant predator?
Exclusion experiments remove the species to see how the abundance of others change
If dominant there’s a loss in biodiversity
Eg; starfish predate herbivores which prevents space domination
Without starfish there would be a barnacle dominated community as barnacles are good at reserving space
Predators prevent competitive exclusion by freeing a resource
Sea urchin + otters example, intense kelp forest grazing
Dispersal filter
Community structure is dominated by this
Geographic barrier which influences which species can move between areas
Oceanic islands
Distance from continent -> fewer subset of species arrive
Environmental filter
Ability to exploit environment in terms of environmental conditions
Abiotic (nonliving) environmental factors that limit the establishment or persistence of certain species in a particular location
Lies within a fundamental niche
Ecological filter
Ability to coexist with other species
Lies within a ‘realised niche’
Appropriate predators/prey
Lack of direct competition
Appropriate symbioses with other indirect interactions
Why do communities vary?
Order of arrival
Established dominance may prevent the establishment of others
Specific mutualists or symbionts
Narrowing a realised niche via competition or inhibition
Conservation application
High alpha = individual sites of importance
High beta = important to conserve multiple sites
Both maintain gamma (overall landscape) diversity
