Biological dispersal
[7][8][9] Dispersal can be distinguished from animal migration (typically round-trip seasonal movement), although within population genetics, the terms 'migration' and 'dispersal' are often used interchangeably.
[12] There are also a number of costs associated with dispersal, which can be thought of in terms of four main currencies: energy, risk, time, and opportunity.
Seeds from the invasive species were shown to be transported by the rivers to natural areas located downstream, thus building upon the already established dispersal distance of the plant.
Human influence through urbanization greatly affects the layout of landscapes, which leads to the limitation of dispersal strategies for many organisms.
Subsequently, this leads to less gene flow between distantly separated populations, in turn decreasing the genetic diversity of each of the areas.
While the urbanization did have a greater effect on mice dispersal, it also led to a slight increase in inbreeding among bat populations.
In general, species significantly vary across the landscape in association with environmental features that influence their reproductive success and population persistence.
[17][18] Spatial patterns in environmental features (e.g. resources) permit individuals to escape unfavorable conditions and seek out new locations.
In addition, the ability of a species to disperse over a gradually changing environment could enable a population to survive extreme conditions.
By contrast, natural barriers to dispersal that limit species distribution include mountain ranges and rivers.
The formation of barriers to dispersal or gene flow between adjacent areas can isolate populations on either side of the emerging divide.
The geographic separation and subsequent genetic isolation of portions of an ancestral population can result in allopatric speciation.
There are numerous animal forms that are non-motile, such as sponges, bryozoans, tunicates, sea anemones, corals, and oysters.
It may seem curious that plants have been so successful at stationary life on land, while animals have not, but the answer lies in the food supply.
Animals fixed in place must rely on the surrounding medium to bring food at least close enough to grab, and this occurs in the three-dimensional water environment, but with much less abundance in the atmosphere.
All of the marine and aquatic invertebrates whose lives are spent fixed to the bottom (more or less; anemones are capable of getting up and moving to a new location if conditions warrant) produce dispersal units.
These may be specialized "buds", or motile sexual reproduction products, or even a sort of alteration of generations as in certain cnidaria.
However, untold millions are produced, and a few do succeed in locating spots of bare limestone, where they settle and transform by growth into a polyp.
[24] On the other hand, small animals utilize the existing kinetic energies in the environment, resulting in passive movement.
Such dormant-resistant stages made possible the long-distance dispersal from one water body to another and broad distribution ranges of many freshwater animals.
[29] Many populations have patchy spatial distributions where separate yet interacting sub-populations occupy discrete habitat patches (see metapopulations).
Dispersing individuals move between different sub-populations which increases the overall connectivity of the metapopulation and can lower the risk of stochastic extinction.
A ship had accidentally released them into the North American Great Lakes and they became a major nuisance in the area, as they began to clog water treatment and power plants.
Another case of this was seen in Chinese bighead and silver carp, which were brought in with the purpose of algae control in many catfish ponds across the U.S.
Unfortunately, some had managed to escape into the neighboring rivers of Mississippi, Missouri, Illinois, and Ohio, eventually causing a negative impact for the surrounding ecosystems.
An environmental response occurs in due to this, as dispersal patterns are important for species to survive major changes.
A study was conducted to test the effects of human-mediated dispersal of seeds over long distances in two species of Brassica in England.
[35] Genome wide SNP dataset and species distribution modelling are examples of computational methods used to examine different dispersal modes.
[34] A genome-wide SNP dataset can be used to determine the genomic and demographic history within the range of collection or observation [Reference needed].
Methods such as these are used to understand the criteria the environment provides when migration and settlement occurs such as the cases in biological invasion.
