Movement and Metapopulations Flashcards
Three phases of movement…
Emigration, Transfer, Immigration
What are four broad aspects of studying movement?
Why move, nature of the movement, environmental drivers of movement and evoloutionary consequences
What are the two categories of dispersal?
Natal and Breeding
Examples of migration patterns…
Resource Patterns - Monarch butterflies south overwinter then four generations migrating north, tracing milk weed
Mule deer and American Elk into high mountain areas in summers, maybe seasonal or food supply
NH terrestial birds move north in spring, breeding with abundant food supplies, then south to savannas when foods abundant after rainy season
Seasonal Migrations
Most common, caused by external seasonal phenomenon, preceded by physiological canges like body fat
Example of migratory conservation…
Alewife fish in freshwater as young, migrating to ocean, blocked by dammming
Managing discharge based on migration patterns.
Example of abstract Active-Passive continuum…
Spiders climb to high place, release gossamer carrying them on winds
Active-Passive continuum seed dispersal…
Passive, however moved by an agent, spikes on herb seeds increase passive carrying on animal coats, or resistance to digestion
Mutalisitc dispersal…
Mites cling to beetles to traverse dung whilst elimintating eggs of flies
Types of Dispersion…
Random
Regular
Aggregated
What are the proximal causes of dispersion?
Evolotuionary triggers favoured by NS and consequences being individuals locations in habitats and interactions
Patchiness
All ecosystems patchy, created abiotically or biotically, grazing or water/moneral depletion
Ecological Grain
Describes the smallest scales at which an ecosystem can respond
Example of ecological grain
Bird view a hickory-oak mixture as a fine grain if they indiscriminately predate, whilst an insect coarse grained if preferentially predating
Turnover Dispersal
Local organism movement into a gap from occupied habitat surrounding it
Why may aggregation dispersal occur?
Conglomerate to favourable habitat, selfishness to decrease predation
Philopatry
Tendency to return to the site of birth for breeding
Philopatry and aggregation dispersal…
High gene proportion and habitat familiarity
What acts against aggregation?
Intensive competition or limitation of resources
Inbreeding as an evolutionary driver of dispersal…
The closer born individuals are, the morel ikely they are related and the more inbed their offspring
Outbreeding Depression
Dispersal where gene combinatiosn break up
Polymorphic Dispersal example…
Some plants produce seeds for both local and wide-range, some performing self pollitnation whislt others germinate underground
Example of sex related diserpsal…
Females more dispersive when males establish and defend territorites or males in polygynandrous as males defend access to groups to females
Example of dispersal affecting population dynamics?
Resources such as seeds for birds can determine where the birds may inhabit:
Dispersal considertion in conservation…
Flying squirrels in Finland due to habitat loss/fragmentation, being a highly dispersive species, with patches for breeding, so physical connectivity important.
Implication for dispersal peturbation on invasion…
North America great lakes invaded by 170 alien species, derived from freight ships mostly and discharge of many containing plants and animals
How may invasvieness be controlled?
Political enforcement of compulsory open ocean discharge or filtration systems
Case study of invasion…
Zebra mussles have massive economic implications: depletion of food and O2 availability, clogging of water intake pipes in hydroelectric plants and water filtration system
Metapopulations
These are dynamically determined by extinction of subpopulatiosn and colonisation rate of new ones by dispersal, thus the role of extinction and colonisation in dynamics
Species Distribution Modelling
A form of model of relationship between environment and species, based on variety of envrionmental variables, allowing spatial predictions
How is SDM performed?
Information collected on where species found, extrapolated against locations they are not, potential habtiatiability
What might limit species colonisation?
Dispersal effectiveness, so information gathered on environmentally variables predicting survivability
Levins Model
Describes temporal changes in regional abundance by extinction and colonisation of metapopulations
Derive dp/dt = cp(1-p)-ep
e is local extinction rate of patches
c is colonisation rate of empty patches
(1-p) depicts empty patches prone to recolonisation
What does dp/dt = cp(1-p)-ep say?
Recolonisation rate increases with (1-0) and with fraction of occupied patches that can provide colonisers, with extinction rate increasing with fraction of patches prone to extinction
What are necessary features of a MP?
Chance of extinction/recolonisation of subpopulation, and independent dynamics of the subpopulations
Example of MP dynamics?
Glenville fritillary butterfly inhabits dry meadows supporting one of its two larval hosts, fragmented 4,500 patches, covering only 1% of total area, split into 125 semi-independent networks
