Metacommunities Flashcards
Lotka-Volterra equations
Equations that describe the relationships between prey and predators
Issues with conventional stud of communities
Conventional views assume that communities are closed and isolated, however additonal ecological processes occur at larger scales.
Metacommunity
Set of local communities linked by dispersal
Metacommunity theory
Describes processes that occur at the metacomunity scale
The importance of dispersal in coexistence
Strongly competing species can coexist regionally through constant interpatch dispersal, and a tradeoff between competitiveness and dispersal capabilities
Mass effects
The occurrence of a species in local communities depend on an influx at a larger, regional scale
Population
Individuals of a single spcies in a habitat patch
Metapopulation
Set of local populations of a species linked by dispersal
Community
Individuals of different species that interact in a defined spatial unit
Metacommunity
A set of of communities in a region, which are linked by dispersal
Microsite
A site capable of holding a single individual
Locality
A spatial unit holding a community
Types of patches (aka localities) and examples
1) Permanent patches (e.g., islands)
2) Temporary patches (e.g., fruiting bodies)
3) Permanent patches with indistinct boundaries and corridors (e.g., ocean currents)
Region
A large spatial unit encompassing multiple localities
Mass effect
A metapopulation dynamic involving a flow of individuals, which is affected by difference in population densities among patches
Rescue effect
Constant recolonization reduces the chance of local extinctions
Source-sink effects
Metacommunity dynamic in which immigration enhances populations size emigration decreases population size
Colonization
Dynaiumc in which species become established in areas in which they were absent
Dispersal
Movement of individuals: Immigration vs emigration
Stochastic extinctions
Extinction events caused by disturbances beyond interacitons with other species
Deterministic extincions
Mechanism in which populations become extinct due to biotic or abiotic interactions
Metacommunity dynamics
Involve interaction of spatial and community mechanics
Classic metapopulation (Levin)
Identical local populations with equal chance of colonization and extincion
Mainland-island system
A system composed of extinction-resistant mainland populations and extinction-prone island populations
Open community
A community that is open to immigration and emigration
Closed comunity
An isolated community in which there is no immigration or emigration
Patch occupancy model
Community model in which local populations are not modeled
Spatially explicit model
Metacommunity model in which movement is influenced by arrangement and distance between patches
Spatially implicit model
Metacommunity model in which arrangement and distance between patches do not influence movement
The four paradigmal approaches to study metacommunities
1) Patch dynamic paradigm
2) Species sorting paradigm
3) Mass effect paradigm
4) Neutral paradigm
Patch dynamic perspective to metacommunity dynamics
Metacommunity paradigm assuming all patches are identical and local species are modeled only by a tradeoff between dispersal and competitiveness
Empirically supported by butterfly metapopulations
Species sorting perspective
Paradigm that explaines metacommunity patterns through environmental gradients, dispersal, and specialization to different patch types instead of dispersal/competitiveness
In this perspective, environmental gradients dictate the local demographies;
Empirically supported by plankton communties
Mass effect perspective
A metacommunity paradigm that proposes species are rescued by immigrations, and that immigration enhance population sizes, while emigrations reduce population sizes.
Empirically supported by bacteria and protist communities, where they added corridors
Neutral perspective
A metacommunity paradigm that assumes all species have equal competitive ability and attributes species patterns to random movement between communities; regarded as a null hypothesis against other community paradigms
Problem with defining communities
Often don’t have discrete boundaries
Problems with describing community processes with paradigms
1) Real ecological communties subject to both habitat ariability and stochastic dynamics
2) metacommunity behaviour depends on how species evolved
Community-wide character displacement
States that locally existing species should be less similar to each other;
Tis view is controversial because communities with species that are more similar are less prone to invasions.
In nature, there’s evidence for both cases.
