Dispersal vector

ferns, the fern catapults its spores 1-2 cm so they can be picked up by a second dispersal vector, often the wind. 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. There are five main types of autochory that act on such seeds or spores: ballochory, or violent ejection by the parent organism; blastochory, or crawling with horizontal runners; barochory, or relying on gravity for dispersal; herpochory, or crawling with fine hair-like structures called trichomes; or being pushed or twisted into the ground by hygromorphic awns in response to humidity changes, e.g. Erodium cicutarium. In some cases, ballochory can be more effective when combined with a secondary dispersal vector: ejecting the seeds or spores in order for them to use wind or water for longer distance dispersal. == Animal dispersal ==

Dispersal by animals is called zoochory. Ornithochory Birds contribute to seed dispersal in several ways that are unique from general vectors. Birds often cache, or store, the seeds of trees and shrubs to consume later. Only some of these seeds are later recovered and eaten, so many of the seeds are able to use the behavior of seed storage to allow them to germinate away from the mother tree. In seed dispersal, ingestion of seeds that can resist digestive juices allows such seeds to be scattered in faeces and dispersed far from the parent organism. Birds act as dispersal vectors for its other types 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, ostracods, and bryozoans. Myrmecochory This includes all of the dispersal caused by ants, including seed dispersal and the dispersal of leaves from trees. Mammaliochory Like birds, mammals disperse units over long distances, especially through carnivores. When carnivores eat herbivores they connect different populations of the same species. This is because predators have larger ranges than their prey. Mammals contribute to bryophyte and fern spore dispersal by carrying spores 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 ecosystems 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. Once consumed, the eggs are spread to a new are when small mounds of dung are passed out. Dispersal by Invertebrates One of the most important examples of dispersal via invertebrates 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, or the ingestion of the plant. == Wind dispersal ==

Anemochory is dispersal of units by wind. Wind is a major agent of long distance dispersal that helps to spread species to new habitats. Each species has its own "wind dispersal potential". This is the proportion of dispersal units (seeds, spores or pollen) that travel farther than a specific distance travelled under normal weather conditions. Its effectiveness relies on the wind conditions and the adaptations of the dispersal units. The two main traits of plants that predict their wind dispersal potential are falling velocity and initial release height of the dispersal unit. Seeds that fall faster are generally heavier. They have a lower wind dispersal potential as they need a stronger wind to carry them. Structural adaptations Many species have evolved structural adaptations to maximize wind dispersal potential. Common examples include plumed, winged, and balloon-like diaspores. Winged diaspores have fibrous tissue that develops on the wall of the seed and projects outward. Some common examples include pine 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 balloon-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, 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, reducing the amount of seeds that are dispersed. This, therefore, lowers the probability that dispersed seeds with germinate and take root. Chemical runoff from fertilizers, leakages of sewage, and carbon emissions from fossil fuels can also lead to eutrophication, a build up of nutrients that often leads to excess algae and invasive 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. Global warming effects on wind patterns can increase average wind velocity. However, it can also lead to lower levels of wind dispersal for each individual plant or organism since global warming affects 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. Barriers such as mountain ranges, farm land, and urban centers prevent the relatively free movement of dispersal units seen in open bodies of water. The process of releasing potential offspring into the water is called broadcast spawning. A number of marine invertebrates require ocean currents to connect their gametes once broadcast spawning has occurred. Kelp, an important group of sea plants, primarily use ocean currents to distribute their spores offspring. Many coral species reproduce by releasing gametes into the water column expecting other local corals to do the same before the original gametes are dispersed by ocean currents. Some non-submerged aquatic plant species, like palm trees and mangroves, have developed fruits that float on sea water in order to use ocean currents to disperse them. Coconuts have been found to travel up to thousands of miles away from their parent tree due to their buoyant nature. Over 100 species of vascular plants use this dispersal method for their fruit. Organisms in shallower waters, such as seagrasses, are crashed upon by waves and pulled out by tides into the open 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 plant parts, such as seeds, fruits, and leaves. Drifting, as discussed above, can help marine mammals move efficiently. It has been shown that intertidal invertebrates at the deepest part of their habitats will travel up to multiple kilometers using sea ice. Freshwater dispersal Freshwater dispersal mainly occurs through flowing water transporting dispersal units. Lakes remain genetically diverse thanks to rivers connecting them to new sources of biodiversity. In these cases, the dispersal units are moved to new aquatic habitats by utilizing the wind instead of the water in their habitat. 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 is dependent on the amount of time that organism or unit is able to be buoyant. Freshwater is important for the dispersal of non-aquatic terrestrial organisms as well. Bryophytes require an external source of water in order to sexually reproduce. Some of them use falling rain drops to disperse their spores as far as possible. Extreme weather Extreme weather events (tropical cyclones, floods and heavy rains, hurricanes, and thunderstorms) are the most intense examples of water functioning as a vector. Floods also displace plants and organisms, whether or not overflow occurs. If a hurricane strikes in the later summer months, more propagules can be expected to be dispersed. However, early hurricanes can wash out immature propagules and decrease the dispersal of mature propagules for that season. Artificial waterways created by humans have also spurred new types of water dispersal. Amphipods were found to be able to cross areas that could not be crossed before to enter a new drainage pipe due to a newly constructed canal. == Human-mediated dispersal ==

We have been acting as dispersal vectors since we began moving around the planet, introducing non-native plants and animals with us. As trends in urbanisation have increased, urban environments help to disperse seeds and bring invasive species with us. Many non-native species exist in urban environments and they can move in and out of urban areas very quickly. This leads to them spreading much more quickly to neighboring environments. ==See also==