A dispersal vector is an agent of biological dispersal that moves a dispersal unit, or

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

, away from its birth population to another location or population in which the individual will reproduce. These dispersal units can range from pollen to seeds to fungi to entire organisms. There are two types of dispersal vector, those that are active and those that are passive. Active dispersal involves organisms that are capable of movement under their own energy. In passive dispersal, the organisms have evolved dispersal units, or propagules, that use the kinetic energy of the environment for movement. In plants, some dispersal units have tissue that assists with dispersal and are called diaspores. Some dispersal is self-driven (autochory), such as using gravity (barochory), and does not rely on external vectors. Other types of dispersal are due to external vectors, which can be biotic vectors, such as animals (zoochory), or abiotic vectors, such as the wind (anemochory) or water (hydrochory). In many cases, organisms will be dispersed by more than one vector before reaching its final destination. It is often a combination of two or more modes of dispersal that act together to maximize dispersal distance, such as wind blowing a seed into a nearby river, that will carry it farther down stream.

Self-generated dispersal

Autochory is the dispersal of diaspores, which are dispersal units consisting of seeds or spores, using only the energy provided by the diaspore or the parent plant. The plant of origin is the dispersal vector itself, instead of an external vector. There are four main types of autochory that act on diaspores: ballochory, or violent ejection by the parent organism; blastochory, where a diaspore crawls along the ground using

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

s; barochory, the use of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

for dispersal; and herpochory, crawling using hygroscopic hairs called

trichome Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a pla ...

s. In some cases, ballochory can be more effective when utilizing a secondary dispersal vector: ejecting the seeds in order for them to use wind or water for longer distance dispersal.

Animal dispersal

Animal-mediated dispersal is called zoochory. Zoochory can be further described by which animal is acting as a dispersal vector. Animals are an important dispersal vector because they provide the ability to transfer dispersal units longer distances than their parent organism can. The main groups include dispersal by

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s (ornithochory), dispersal by

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

s (

myrmecochory Myrmecochory ( (sometimes myrmechory); from grc, μύρμηξ, mýrmēks ("ant") and ''khoreíā'' ("circular dance") is seed dispersal by ants, an ecologically significant ant–plant interaction with worldwide distribution. Most myrmeco ...

), dispersal by

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s (mammaliochory), dispersal by

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

s or

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s, and dispersal by

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, such as bees. Animals are also a large contributor to

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...

via

zoophily Zoophily, or zoogamy, is a form of pollination whereby pollen is transferred by animals, usually by invertebrates but in some cases vertebrates, particularly birds and bats, but also by other animals. Zoophilous species frequently have evolved ...

. Flowering plants overwhelmingly are pollinated by animals, and while

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s are involved in the majority of that pollination, birds and mammals also play a role.

Ornithochory

Bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s contribute to

seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

in several ways that are unique from general vectors. Birds often cache, or store, the seeds of trees and shrubs for later consumption; only some of these seeds are later recovered and eaten, so many of the seeds are able to utilize the behavior of seed caching to allow them to

germinate Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

away from the mother tree. Long-distance dispersal, which is rare for a parent plant to achieve alone, could be mediated by migratory movements of birds. Long-distance dispersal operates over spatial areas that span thousands of kilometers, which allow it to promote rapid range shifts and determine species distributions. In

ingestion Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms ingest ...

of seeds that are capable of resisting digestive juices allows the

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

s to be scattered in feces and dispersed far from the parent organism. For these seeds, gut passage enhances

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

ability when the seeds are ingested by

s and

s. Finally, ingestion of

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

s by carnivorous animals may help disperse seeds by preying on primary seed dispersers such as herbivores or

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

s. When a bird is eaten by a cat or another carnivore, that animal will inadvertently consume the seeds that the prey species consumed. These seeds may then be later deposited in a process called

diplochory Diplochory, also known as “secondary dispersal”, “indirect dispersal” or "two-phase dispersal", is a seed dispersal mechanism in which a plant's seed is moved sequentially by more than one dispersal mechanism or vector. The significance of ...

, where a seed is moved by more than one dispersal vector, which is important for seed dispersal outcomes as carnivores range widely and enhance the genetic connectivity of dispersed populations. Birds act as dispersal vectors for non-seed dispersal units as well. Hummingbirds spread pollen on their beaks, and fungal spores may stick to the bottom of birds’ feet. Water birds may also help to disperse aquatic invertebrates, specifically

branchiopods Branchiopoda is a class (biology), class of crustaceans. It comprises Anostraca, fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca and the Devonian ''Lepidocaris''. They are mostly small, freshwater animals that feed on plankton ...

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typi ...

s, and

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

ns.

Myrmecochory

This includes all of the dispersal caused by

s, including seed dispersal and the dispersal of leaf matter from trees.

Mammaliochory

Similarly to birds, dispersal by

s allows for long distance dispersal, especially via carnivores. The act of carnivores eating primary dispersal vectors (herbivores) can lead to long distance dispersal and connection between different populations of the same species because of large predator ranges in comparison to smaller herbivore ranges. Mammals have been shown to act as dispersal vectors for seeds, spores, and

parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

. Just as in ornithocory, ingestion by herbivores acts as a dispersal vector for seeds, and gut passage increases the rate of

Marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...

s, and some species in the suborder

Feliformia Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats (large and small), hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, Canifor ...

( Cape grey mongooses and

Cape genet The Cape genet (''Genetta tigrina''), also known as the South African large-spotted genet, is a genet species endemic to South Africa. As it is common and not threatened, it is listed as Least Concern on the IUCN Red List. Like other genets, it ...

s) have all been identified as pollinators. Non-flying mammals have been identified as acting as pollinators in Australia, Africa, South and Central America. Some plants may have traits that coevolved to utilize mammals as dispersal vectors, such as being extremely pungent in odor, nocturnal nectar production, and robust flowers that can handle rough feeders. The

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

of some plants can be found stuck to the fur of mammals as well as accidentally ingested when

nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...

is consumed. Deer_Mouse_(Peromyscus_maniculatus)_(9310532204)

Mammals contribute to

bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in ...

and

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

spore dispersal by carrying

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s on their fur. Small mammals acting as dispersal vectors may have advantages for the dispersing organism compared to wind transport, as the mammals share similar

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s to the parent plant, while wind transport is random. Additionally, mammals can transport spores that have qualities such as low production and non-wind adapted morphology that wouldn't be conducive for wind transport.

Dik-dik A dik-dik is the name for any of four species of small antelope in the genus ''Madoqua'' that live in the bushlands of eastern and southern Africa. Dik-diks stand about at the shoulder, are long, weigh and can live for up to 10 years. Dik- ...

, (''Madoqua kirkii''),

Grant's gazelle Grant's gazelle (''Nanger granti'') is a species of gazelle distributed from northern Tanzania to South Sudan and Ethiopia, and from the Kenyan coast to Lake Victoria. Its Swahili name is ''swala granti''.impala (''Aepyceros melampus'') become infected by gastrointestinal nematode parasites that lay on vegetation the antelope consume. Once infected, they disperse

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

in their feces. Once consumed, the eggs are spread to a new area via the defecation of small mounds of dung.

Dispersal by amphibians or reptiles

Frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s and

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s have been found to be dispersal vectors for

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s and ring worms, specifically bromeliad

s (''Elpidium bromeliarum)'' and

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

s (''Dero superterrenus''). Annelids showed a strong chemical orientation towards moist frog skin that may have developed to diminish risk of dehydration during transport in the environment. The ostracods have frequently been found to be attached to frogs in order to colonize new areas. Both ostracods and annelids will attach themselves to lizards as well, but they prefer to attach themselves to frogs.

Dispersal by Invertebrates

One of the most important examples of dispersal via

s are pollinators such as bees, flies, wasps, beetles, and butterflies. Invertebrates may also act as dispersal vectors for the spores of ferns and bryophytes via

endozoochory In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

, or the ingestion of the plant.

Wind dispersal

Anemochory is dispersal of units by wind. Wind is a major vector of long distance dispersal that is responsible for the spread and propagation of species to new habitats. Each species has its own "wind dispersal potential", which is the proportion of dispersal units that travel farther than a predefined reference distance travelled under normal

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...

conditions. The effectiveness of wind dispersal relies predominantly on the morphological traits and adaptations of the dispersal units and wind conditions. The two main traits of plants that predict their wind dispersal potential are falling

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...

and initial release height of the dispersal unit. Higher falling velocity is generally correlated with heavier seeds, which have a lower wind dispersal potential because it takes a stronger wind to carry them. The taller the initial release height of the dispersal unit, the larger the wind dispersal potential because there is a larger window in which it can be picked up by the wind.

Adaptive morphology

Many species have evolved morphological adaptations to maximize wind dispersal potential. Common examples include plumed, winged, and balloon-like diaspores. Waiting_For_The_Wind_(222218757)

Plumed diaspores have thin hair-like projections that allow easier wind uplift. One of the most common plumed species is the dandelion, ''Taraxacum officinale''. The wind dispersal potential of plumed species are directly correlated to the total mass and total surface area of the projected plume. Picea_abies_seeds_with_wings

Winged diaspores have fibrous tissue that develops on the wall of the seed and projects outward. Seed wings are generally thought to co-evolve with the evolution of larger seeds, in order to increase dispersal and offset the weight of the larger seeds. Some common examples include

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...

and spruce trees. Balloon-like seeds are a phenomenon where the calyx, a kind of protective pouch or covering the plant uses to guard the seeds, is light and swollen. This ballon-like structure allows the entire pouch of seeds to be dispersed by gusts of wind. A common example of the balloon-like diaspore is the ''

Trifolium fragiferum ''Trifolium fragiferum'', the strawberry clover, is a herbaceous perennial plant species in the bean family Fabaceae. It is native to Europe, Asia, and parts of Africa. It is present in other places, such as sections of North America, as an intro ...

,'' or strawberry clover.

Human effects on anemochory

Wind dispersal of a particular species can also be affected by human actions. Humans can affect anemochory in three major ways: habitat fragmentation, chemical runoff, and climate change. Clearing land for development and building roads through forests can lead to habitat fragmentation. Habitat fragmentation reduces the number and size of the effected populations, which reduces the amount of seeds that are dispersed. This lowers the probability that dispersed seeds with germinate and take root. Chemical runoff from fertilizer, leakages of sewage, and carbon emissions from

fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...

s can also lead to

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

, a build up of nutrients that often leads to excess algae and non-native plant growth. Eutrophication can lead to decreased long distance dispersal because the lack of nutrients to native plants causes a decrease in seed release height. However, because of the lowered release height, eutrophication can sometimes lead to an increase in short distance dispersal. Climate change effects on wind patterns have the potential increase average wind velocity. However, it can also lead to lower levels of wind dispersal for each individual plant or organism because of the effects

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

has on the normal conditions needed for plant growth, such as temperature and rainfall.

Water dispersal

Hydrochory is dispersal using water, including oceans, rivers, streams, and rain. It affects many different dispersal units, such as seeds, fern spores,

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

, and

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

. Terrestrial water sources tend to be more restricted in their ability to disperse units. Barriers such as mountain ranges, farm land, and urban centers prevent the relatively free movement of dispersal units seen in open bodies of water.

Oceanic dispersal Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between isla ...

can move individuals or reproductive propagules anywhere from a meter to hundreds of kilometers from the original point depending on the size of the individual.

Marine dispersal

A majority of marine organisms utilize

ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours ...

s and movement within the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

to reproduce. The process of releasing reproductive propagules into the water is called broadcast

spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquat ...

. While broadcast spawning requires parents to be relatively close to each other for fertilization, the fertilized

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

s can be moved extreme distances. A number of marine invertebrates require ocean currents to connect their gametes once broadcast spawning has occurred.

Kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwa ...

, an important group of sea plants, primarily utilize ocean currents to distribute their spores and larvae. Many coral species reproduce by releasing gametes into the water column with hopes that other local corals will also release gametes before these units are dispersed by ocean currents. Some non-submerged aquatic plant species, like palm trees and mangroves, have developed fruits that float in sea water in order to utilize ocean currents as a form of dispersal. Coconuts have been found to travel up to thousands of miles away from their parent tree due to their

buoyant Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pr ...

nature. A variety of over 100 species of vascular plants utilize this dispersal method for their fruit. Many plants have evolved with specific adaptations to maximize the distance that seeds, fruits, or propagules are dispersed in the ocean. For an increased protection against sinking in the

, seeds have developed hair or slime on their outer seed coats. Seeds with filled with air, cork, or oil are better prepared to float for farther distances. Another aspect of dispersal comes from wave and tidal action. Organisms in shallower waters, such as seagrasses, become displaced and dispersed by waves crashing upon them and tides pulling them out into the open ocean. Table iceberg west of Sjuøyane, Arctic ocean

Table iceberg west of Sjuøyane, Arctic ocean

Some smaller marine organisms maximize their own dispersal by attaching to a raft - a biotic or abiotic object that is being moved by the ocean’s currents. Biotic rafts can be floating seeds or fruits, leaves, or other propagules. Abiotic rafts are usually floating woods or plastics, including buoys and discarded trash. Sea ice is also an important dispersal vector. Some arctic species rely on sea ice to disperse their eggs, like ''Daphnia pulex.'' Drifting, as discussed above, can be an effective dispersal vector for marine mammals. It has been shown that intertidal

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

invertebrates will utilize sea ice as a raft to travel up to multiple kilometers.

Freshwater dispersal

Freshwater dispersal primarily occurs through flowing water transporting dispersal units. Permanent aquatic environments require outside forms of dispersal to retain biodiversity, so hydrochory via freshwater is vital for the success of terrestrial water sources. Lakes remain genetically diverse thanks to rivers that connect lakes to new sources of biodiversity. In lakes that lack connecting rivers, some organisms have developed adaptations that utilize the wind, while in an aquatic environment, to disperse reproductive units. In these cases, the dispersal units are moved to new aquatic habitats by utilizing the wind instead of the water in their habitat. The Flowing River

Running water is the only form of long distance dispersal present in freshwater sources, so rivers act as the main aquatic terrestrial dispersal vector. Like in marine ecosystems, organisms take advantage of flowing water via passive transport of drifting along on a raft. The distance traveled by floating or drifting organisms and propagules is determined primarily on the amount of time that organism or unit is able to retain

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...

. Freshwater is important for dispersal of non-aquatic terrestrial organisms as well.

Bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in ...

s require an external source of water in order to sexually reproduce. Some bryophytes also utilize falling rain drops to maximize their spore dispersal distances.

Extreme weather

Extreme weather Extreme weather or extreme climate events includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Often, extreme events are based on a locat ...

events (

tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...

s, floods and heavy rains, hurricanes, and thunderstorms) are the most intense examples of water functioning as a vector. The high intensity and high volume of rain that comes with these events facilitate long distance dispersal. Overflow is traditionally a side effect of heavy rains impacting one specific area. Overflows have been shown to be effective in transmitting

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

between temporary lakes and ponds. The overflow of pool water acts as an important passive form of

hydrochory In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

in which water acts as a vector. Floods displace plants and organisms, whether or not overflow occurs.

Macrophytes Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

and organisms as small as

can be transported via flood pulses. Hurricanes can also act as dispersal vectors. After the 2004 Hurricane Charley struck Florida, there was a higher reported dispersal of the propagules of red mangrove trees. If a hurricane strikes in the later summer months, there is an expected increase in the dispersal of propagules, while early storms can wash out immature propagules and decrease the dispersal of mature propagules for that season. When extreme weather events occur over an open body of water, they can create intense waves. These waves can create large dispersal within the water column by changing local water movement, but tend to constrict the actual dispersal distance for smaller organisms.

Human-created hydrochory

The

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...

industry has introduced new forms in which water acts as a dispersal vector. The water in bait buckets transfers bait everywhere a fisherman takes it, and this can introduce non-native species into areas should this bait water be spilt. This idea is applied on a much larger scale to the ballast tanks of ships. A study done by James Carlton of Williams College reports that more than 3000 species are moving across the ocean in ballast tanks on any given day. Artificial waterways created by humans have also spurred new forms of hydrochory.

Amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far describ ...

were found to be able to cross previously uncrossable areas to enter into new drainage pipe thanks to the construction of a canal. Artificial waterways not only connect communities that are geographically close, but they also allow for the transmission of invasive species from distant communities. The distribution of invasive species is, in part, regulated by local ocean conditions and currents. The introduction of human-generated waste, like wood planks and plastic bags, into water sources has increased the amount of viable rafts for dispersal.

Human-mediated dispersal

Humans have been acting as dispersal vectors since we began moving around the planet, bringing non-native plants and animals with us. As trends in

urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...

have increased, urban environments can act as staging grounds for species dispersal and invasion. Many non-native species exist in urban environments and the high rate of movement in and out of urban areas leads to a high level of dispersal to neighboring environments.{{Cite journal, last=von der Lippe, first=Moritz, date=Spring 2017, title=Do cities export biodiversity? Traffic asdispersal vector across urban–rural gradients, url=http://onlinelibrary.wiley.com/store/10.1111/j.1472-4642.2007.00401.x/asset/j.1472-4642.2007.00401.x.pdf;jsessionid=8555AE925BA4D1C18843B13F46A32974.f02t02?v=1&t=j294fnqv&s=78921d79a70a42912d1459f33ed3ab99074443cc, journal=Diversity and Distributions, volume=14, pages=18–25, doi=10.1111/j.1472-4642.2007.00401.x

References

Reproduction Population ecology