Seed dispersal

Seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have very limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic vectors such as the wind and living (biotic) vectors like birds. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water, and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus.

Epilobium hirsutum - Seed head - Triptych
Epilobium hirsutum seed head dispersing seeds

Benefits

Seed dispersal is likely to have several benefits for different plant species. First, seed survival is often higher away from the parent plant. This higher survival may result from the actions of density-dependent seed and seedling predators and pathogens, which often target the high concentrations of seeds beneath adults.[1] Competition with adult plants may also be lower when seeds are transported away from their parent.

Seed dispersal also allows plants to reach specific habitats that are favorable for survival, a hypothesis known as directed dispersal. For example, Ocotea endresiana (Lauraceae) is a tree species from Latin America which is dispersed by several species of birds, including the three-wattled bellbird. Male bellbirds perch on dead trees in order to attract mates, and often defecate seeds beneath these perches where the seeds have a high chance of survival because of high light conditions and escape from fungal pathogens.[2] In the case of fleshy-fruited plants, seed-dispersal in animal guts (endozoochory) often enhances the amount, the speed, and the asynchrony of germination, which can have important plant benefits.[3]

Seeds dispersed by ants (myrmecochory) are not only dispersed short distances but are also buried underground by the ants. These seeds can thus avoid adverse environmental effects such as fire or drought, reach nutrient-rich microsites and survive longer than other seeds.[4] These features are peculiar to myrmecochory, which may thus provide additional benefits not present in other dispersal modes.[5]

Finally, at another scale, seed dispersal may allow plants to colonize vacant habitats and even new geographic regions.[6] Dispersal distances and deposition sites depend on the movement range of the disperser, and longer dispersal distances are sometimes accomplished through diplochory, the sequential dispersal by two or more different dispersal mechanisms. In fact, recent evidence suggests that the majority of seed dispersal events involves more than one dispersal phase.[7]

Types

Seed dispersal is sometimes split into autochory (when dispersal is attained using the plant's own means) and allochory (when obtained through external means).

Long distance

Long distance seed dispersal (LDD) is a type of spatial dispersal that is currently defined by two forms, proportional and actual distance. A plant's fitness and survival may heavily depend on this method of seed dispersal depending on certain environmental factors. The first form of LDD, proportional distance, measures the percentage of seeds (1% out of total number of seeds produced) that travel the farthest distance out of a 99% probability distribution.[8][9] The proportional definition of LDD is in actuality a descriptor for more extreme dispersal events. An example of LDD would be that of a plant developing a specific dispersal vector or morphology in order to allow for the dispersal of its seeds over a great distance. The actual or absolute method identifies LDD as a literal distance. It classifies 1 km as the threshold distance for seed dispersal. Here, threshold means the minimum distance a plant can disperse its seeds and have it still count as LDD.[10][9] There is a second, unmeasurable, form of LDD besides proportional and actual. This is known as the non-standard form. Non-standard LDD is when seed dispersal occurs in an unusual and difficult-to-predict manner. An example would be a rare or unique incident in which a normally-lemur-dependent deciduous tree of Madagascar was to have seeds transported to the coastline of South Africa via attachment to a mermaid purse (egg case) laid by a shark or skate.[11][12][13][6] A driving factor for the evolutionary significance of LDD is that it increases plant fitness by decreasing neighboring plant competition for offspring. However, it is still unclear today as to how specific traits, conditions and trade-offs (particularly within short seed dispersal) effect LDD evolution.

Autochory

Geranium sanguineum02
The "bill" and seed dispersal mechanism of Geranium pratense

Autochorous plants disperse their seed without any help from an external vector, as a result this limits plants considerably as to the distance they can disperse their seed.[14] Two other types of autochory not described in detail here are blastochory, where the stem of the plant crawls along the ground to deposit its seed far from the base of the plant, and herpochory (the seed crawls by means of trichomes and changes in humidity).[15]

Gravity

Barochory or the plant use of gravity for dispersal is a simple means of achieving seed dispersal. The effect of gravity on heavier fruits causes them to fall from the plant when ripe. Fruits exhibiting this type of dispersal include apples, coconuts and passionfruit and those with harder shells (which often roll away from the plant to gain more distance). Gravity dispersal also allows for later transmission by water or animal.[16]

Ballistic dispersal

Ballochory is a type of dispersal where the seed is forcefully ejected by explosive dehiscence of the fruit. Often the force that generates the explosion results from turgor pressure within the fruit or due to internal tensions within the fruit.[14] Some examples of plants which disperse their seeds autochorously include: Impatiens spp., Arceuthobium spp., Ecballium spp., Geranium spp., Cardamine hirsuta and others. An exceptional example of ballochory is Hura crepitans—this plant is commonly called the dynamite tree due to the sound of the fruit exploding. The explosions are powerful enough to throw the seed up to 100 meters.[17]

Witch hazel uses ballistic dispersal without explosive mechanisms by simply squeezing the seeds out at 28 mph.[18]

Allochory

Allochory refers to any of many types of seed dispersal where a vector or secondary agent is used to disperse seeds. This vectors may include wind, water, animals or others.

Wind

Photos-photos 1088103921 Floating
Wind dispersal of dandelion seeds
Entada phaseoloides MHNT graines
Entada phaseoloides – Hydrochory

Wind dispersal (anemochory) is one of the more primitive means of dispersal. Wind dispersal can take on one of two primary forms: seeds can float on the breeze or alternatively, they can flutter to the ground.[19] The classic examples of these dispersal mechanisms, in the temperate northern hemisphere, include dandelions, which have a feathery pappus attached to their seeds and can be dispersed long distances, and maples, which have winged seeds (samaras) and flutter to the ground. An important constraint on wind dispersal is the need for abundant seed production to maximize the likelihood of a seed landing in a site suitable for germination. There are also strong evolutionary constraints on this dispersal mechanism. For instance, Cody and Overton (1996) found that species in the Asteraceae on islands tended to have reduced dispersal capabilities (i.e., larger seed mass and smaller pappus) relative to the same species on the mainland.[20] Also, Helonias bullata, a species of perennial herb native to the United States, evolved to utilize wind dispersal as the primary seed dispersal mechanism; however, limited wind in its habitat prevents the seeds to successfully disperse away from its parents, resulting in clusters of population.[21] Reliance on wind dispersal is common among many weedy or ruderal species. Unusual mechanisms of wind dispersal include tumbleweeds, where the entire plant (except for the roots) is blown by the wind. Physalis fruits, when not fully ripe, may sometimes be dispersed by wind due to the space between the fruit and the covering calyx which acts as air bladder.

Water

Many aquatic (water dwelling) and some terrestrial (land dwelling) species use hydrochory, or seed dispersal through water. Seeds can travel for extremely long distances, depending on the specific mode of water dispersal; this especially applies to fruits which are waterproof and float on water.

The water lily is an example of such a plant. Water lilies' flowers make a fruit that floats in the water for a while and then drops down to the bottom to take root on the floor of the pond. The seeds of palm trees can also be dispersed by water. If they grow near oceans, the seeds can be transported by ocean currents over long distances, allowing the seeds to be dispersed as far as other continents.

Mangrove trees grow directly out of the water; when their seeds are ripe they fall from the tree and grow roots as soon as they touch any kind of soil. During low tide, they might fall in soil instead of water and start growing right where they fell. If the water level is high, however, they can be carried far away from where they fell. Mangrove trees often make little islands as dirt and detritus collect in their roots, making little bodies of land.

A special review for oceanic waters hydrochory can be seen at oceanic dispersal.

Animals

Bur Macro BlackBg
The small hooks of the surface of a bur enable attachment to animal fur for dispersion.

Animals can disperse plant seeds in several ways, all named zoochory. Seeds can be transported on the outside of vertebrate animals (mostly mammals), a process known as epizoochory. Plant species transported externally by animals can have a variety of adaptations for dispersal, including adhesive mucus, and a variety of hooks, spines and barbs.[22] A typical example of an epizoochorous plant is Trifolium angustifolium, a species of Old World clover which adheres to animal fur by means of stiff hairs covering the seed.[6] Epizoochorous plants tend to be herbaceous plants, with many representative species in the families Apiaceae and Asteraceae.[22] However, epizoochory is a relatively rare dispersal syndrome for plants as a whole; the percentage of plant species with seeds adapted for transport on the outside of animals is estimated to be below 5%.[22] Nevertheless, epizoochorous transport can be highly effective if seeds attach to wide-ranging animals. This form of seed dispersal has been implicated in rapid plant migration and the spread of invasive species.[6]

Seed dispersal via ingestion by vertebrate animals (mostly birds and mammals), or endozoochory, is the dispersal mechanism for most tree species.[23] Endozoochory is generally a coevolved mutualistic relationship in which a plant surrounds seeds with an edible, nutritious fruit as a good food for animals that consume it. Birds and mammals are the most important seed dispersers, but a wide variety of other animals, including turtles, fish, and insects (e.g. tree wētā and scree wētā), can transport viable seeds.[24][25] The exact percentage of tree species dispersed by endozoochory varies between habitats, but can range to over 90% in some tropical rainforests.[23] Seed dispersal by animals in tropical rainforests has received much attention, and this interaction is considered an important force shaping the ecology and evolution of vertebrate and tree populations.[26] In the tropics, large animal seed dispersers (such as tapirs, chimpanzees, toucans and hornbills) may disperse large seeds with few other seed dispersal agents. The extinction of these large frugivores from poaching and habitat loss may have negative effects on the tree populations that depend on them for seed dispersal and reduce genetic diversity.[27][28] A variation of endozoochory is regurgitation rather than all the way through the digestive tract.[29]

Seed dispersal by ants (myrmecochory) is a dispersal mechanism of many shrubs of the southern hemisphere or understorey herbs of the northern hemisphere.[4] Seeds of myrmecochorous plants have a lipid-rich attachment called the elaiosome, which attracts ants. Ants carry such seeds into their colonies, feed the elaiosome to their larvae and discard the otherwise intact seed in an underground chamber.[30] Myrmecochory is thus a coevolved mutualistic relationship between plants and seed-disperser ants. Myrmecochory has independently evolved at least 100 times in flowering plants and is estimated to be present in at least 11 000 species, but likely up to 23 000 or 9% of all species of flowering plants.[4] Myrmecochorous plants are most frequent in the fynbos vegetation of the Cape Floristic Region of South Africa, the kwongan vegetation and other dry habitat types of Australia, dry forests and grasslands of the Mediterranean region and northern temperate forests of western Eurasia and eastern North America, where up to 30–40% of understorey herbs are myrmecochorous.[4]

Seed predators, which include many rodents (such as squirrels) and some birds (such as jays) may also disperse seeds by hoarding the seeds in hidden caches.[31] The seeds in caches are usually well-protected from other seed predators and if left uneaten will grow into new plants. In addition, rodents may also disperse seeds via seed spitting due to the presence of secondary metabolites in ripe fruits.[32] Finally, seeds may be secondarily dispersed from seeds deposited by primary animal dispersers, a process known as diplochory. For example, dung beetles are known to disperse seeds from clumps of feces in the process of collecting dung to feed their larvae.[33]

Other types of zoochory are chiropterochory (by bats), malacochory (by molluscs, mainly terrestrial snails), ornithochory (by birds) and saurochory (by non-bird sauropsids). Zoochory can occur in more than one phase, for example through diploendozoochory, where a primary disperser (an animal that ate a seed) along with the seeds it is carrying is eaten by a predator that then carries the seed further before depositing it.[34]

Humans

Epizoochoria NRM
Epizoochory in Bidens tripartita; the seeds have attached to the clothes of a human.
Seed dispersal by a car

Dispersal by humans (anthropochory) used to be seen as a form of dispersal by animals. It's most widespread and intense cases account for the planting of much of the land area on the planet, through agriculture. In this case, human societies form a long term relationship with plant species, and create conditions for their growth.

Recent research points out that human dispersers differ from animal dispersers by having a much higher mobility, based on the technical means of human transport.[35] On the one hand, dispersal by humans also acts on smaller, regional scales and drives the dynamics of existing biological populations. On the other hand, dispersal by humans may act on large geographical scales and lead to the spread of invasive species.[36]

Humans may disperse seeds by many various means and some surprisingly high distances have been repeatedly measured.[37] Examples are: dispersal on human clothes (up to 250 m),[38] on shoes (up to 5 km),[35] or by cars (regularly ~ 250 m, singles cases > 100 km).[39]

Deliberate seed dispersal also occurs as seed bombing. This has risks, as unsuitable provenance may introduce genetically unsuitable plants to new environments.

Consequences

Seed dispersal has many consequences for the ecology and evolution of plants. Dispersal is necessary for species migrations, and in recent times dispersal ability is an important factor in whether or not a species transported to a new habitat by humans will become an invasive species.[40] Dispersal is also predicted to play a major role in the origin and maintenance of species diversity. For example, myrmecochory increased the rate of diversification more than twofold in plant groups in which it has evolved because myrmecochorous lineages contain more than twice as many species as their non-myrmecochorous sister groups.[41] Dispersal of seeds away from the parent organism has a central role in two major theories for how biodiversity is maintained in natural ecosystems, the Janzen-Connell hypothesis and recruitment limitation.[1] Seed dispersal is essential in allowing forest migration of flowering plants.

In addition, the speed and direction of wind are highly influential in the dispersal process and in turn the deposition patterns of floating seeds in the stagnant water bodies. The transportation of seeds is led by the wind direction. This effects colonization situated on the banks of a river or to wetlands adjacent to streams relative to the distinct wind directions. The wind dispersal process can also effect connections between water bodies. Essentially, wind plays a larger role in the dispersal of waterborne seeds in a short period of time, days and seasons, but the ecological process allows the process to become balanced throughout a time period of several years. The time period of which the dispersal occurs is essential when considering the consequences of wind on the ecological process.

See also

References

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Further reading

  • Ridley, Henry N (1930). The Dispersal of Plants Throughout the World. Ashford, Kent: L. Reeve & Co. ISBN 978-0-85393-004-4.

External links

Aril

An aril (pronounced ), also called an arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode or false aril is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ovary (from the funiculus or hilum), an arillode forms from a different point on the seed coat. The term "aril" is sometimes applied to any fleshy appendage of the seed in flowering plants, such as the mace of the nutmeg seed. Arils and arillodes are often edible enticements that encourage animals to transport the seed, thereby assisting in seed dispersal. Pseudarils are aril-like structures commonly found on the pyrenes of Burseraceae species that develop from the mesocarp of the ovary. The fleshy, edible pericarp splits neatly in two halves, then falling away or being eaten to reveal a brightly coloured pseudaril around the black seed.

The aril may create a fruit-like structure, called (among other names) a false fruit. False fruit are found in numerous Angiosperm taxa. The edible false fruit of the longan, lychee and ackee fruits are highly developed arils surrounding the seed rather than a pericarp layer. Such arils are also found in a few species of gymnosperms, notably the yews and related conifers such as the lleuque and the kahikatea. Instead of the woody cone typical of most gymnosperms, the reproductive structure of the yew consists of a single seed that becomes surrounded by a fleshy, cup-like covering. This covering is derived from a highly modified cone scale.

Cassia fistula

Cassia fistula, commonly known as golden shower, purging cassia, or Indian laburnum, is a flowering plant in the subfamily, Caesalpiniaceae of the legume family, Fabaceae. The species is native to the Indian subcontinent and adjacent regions of Southeast Asia. It ranges from eastward throughout India to Myanmar and Thailand and south to Sri Lanka and southern Pakistan. It is a popular ornamental plant and is also used in herbal medicine. It is both the national tree and national flower of Thailand. It is the state flower of Kerala in India.

Convergent evolution

Convergent evolution is the independent evolution of similar features in species of different lineages. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy. The recurrent evolution of flight is a classic example, as flying insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are analogous, whereas homologous structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions.

The opposite of convergence is divergent evolution, where related species evolve different traits. Convergent evolution is similar to parallel evolution, which occurs when two independent species evolve in the same direction and thus independently acquire similar characteristics; for instance, gliding frogs have evolved in parallel from multiple types of tree frog.

Many instances of convergent evolution are known in plants, including the repeated development of C4 photosynthesis, seed dispersal by fleshy fruits adapted to be eaten by animals, and carnivory.

Defaunation

Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.It is estimated that more than 50 percent of all wildlife has been lost in the last 40 years. in 2020 it is estimated that 68% of the world's wildlife will be lost. In South America, there is believed to be a 70 percent loss.In November 2017, over 15,000 scientists around the world issued a second warning to humanity, which, among other things, urged for the development and implementation of policies to halt "defaunation, the poaching crisis, and the exploitation and trade of threatened species."

Elaiosome

Elaiosomes (Ancient Greek: ἔλαιον olive oil + élaion "oil" and σόμα sóma "body") are fleshy structures that are attached to the seeds of many plant species. The elaiosome is rich in lipids and proteins, and may be variously shaped. Many plants have elaiosomes that attract ants, which take the seed to their nest and feed the elaiosome to their larvae. After the larvae have consumed the elaiosome, the ants take the seed to their waste disposal area, which is rich in nutrients from the ant frass and dead bodies, where the seeds germinate. This type of seed dispersal is termed myrmecochory from the Greek "ant" (myrmex) and "circular dance" (khoreíā). This type of symbiotic relationship appears to be mutualistic, more specifically dispersive mutualism according to Ricklefs, R.E. (2001), as the plant benefits because its seeds are dispersed to favorable germination sites, and also because it is planted (carried underground) by the ants.

Elaiosomes develop in various ways either from seed tissues (chalaza, funiculus, hilum, raphe-antiraphe) or from fruit tissues (exocarp, receptacle, flower tube, perigonium, style or spicule). The various origins and developmental pathways apparently all serve the same main function, i.e. attracting ants. Because elaiosomes are present in at least 11,000, but possibly up to 23,000 species of plants, elaiosomes are a dramatic example of convergent evolution in flowering plants.

Erodium cicutarium

Erodium cicutarium, also known as redstem filaree, redstem stork's bill, common stork's-bill or pinweed, is a herbaceous annual – or in warm climates, biennial – member of the family Geraniaceae of flowering plants. It is native to Macaronesia, temperate Eurasia and north and northeast Africa, and was introduced to North America in the eighteenth century, where it has since become naturalized, particularly of the deserts and arid grasslands of the southwestern United States.

Frugivore

A frugivore is an animal that thrives mostly on raw fruits, succulent fruit-like vegetables, roots, shoots, nuts and seeds. It can be any type of herbivore or omnivore where fruit is a preferred food type. Because approximately 20% of all mammalian herbivores also eat fruit, frugivory is common among mammals. Since frugivores eat a lot of fruit, they are highly dependent on the abundance and nutritional composition of fruits. Frugivores can either benefit fruit-producing plants by dispersing seeds, or they can hinder plants by digesting seeds along with the fruits. When both the fruit-producing plant and the frugivore species benefit by fruit-eating behavior, their interaction is called mutualism.

Harvester ant

Harvester ant, also known as harvesting ant, is a common name for any of the species or genera of ants that collect seeds (called seed predation), or mushrooms as in the case of Euprenolepis procera, which are stored in the nest in communal chambers called granaries. They are also referred to as Agricultural ants. Seed harvesting by some desert ants is an adaptation to the lack of typical ant resources such as prey or honeydew from hemipterans. Harvester ants increase seed dispersal and protection, and provide nutrients that increase seedling survival of the desert plants. In addition, ants provide soil aeration through the creation of galleries and chambers, mix deep and upper layers of soil, and incorporate organic refuse into the soil.

Helonias

Helonias bullata (swamp pink) is a rare perennial rhizomatous herb native to the eastern United States, the only known species in the genus Helonias. The root system is extensive in comparison to the apparent size of the plant on the surface. Blooming in March to May, its fragrant flowers are pink and occur in a cluster at the end a vertical spike which may reach up to 3' in height. It has evergreen, lance-shaped, and parallel-veined leaves ranging from dark green to light yellow green in color that form a basal rosette.Swamp pink is a federally threatened species that was historically distributed from Staten Island, New York to the southern Appalachians. Currently, New Jersey supports the largest and most numerous populations, but there are populations in six other states: Delaware; Maryland; Virginia; West Virginia;North Carolina; South Carolina, and Georgia. There is also some unverified indication that a population of swamp pink has survived on Staten Island. Populations of swamp pink are on occasion subject to poaching by plant enthusiasts and others who prize the early bright pink blooms. Unfortunately, the poached plants likely do not survive their move owing to the high sensitivity to being removed from the water saturated environment, underestimation of the size of the root mass, and failure to replicate the necessary environment sufficiently.United States Fish and Wildlife Service has instituted a volunteer monitoring project, “Adopt-a-Swamp-Pink Population”. The program has been further expanded by a joint volunteer effort with Citizens United to Protect the Maurice River and Its Tributaries, Inc.. The survey results are shared with U.S.F.W.S. and the New Jersey Natural Heritage database.

Igapó

Igapó (Portuguese pronunciation: [igaˈpɔ], from Old Tupi: "root forest") is a word used in Brazil for blackwater-flooded forests in the Amazon biome. These forests and similar swamp forests are seasonally inundated with freshwater. They typically occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are found in a range of climate zones, from boreal through temperate and subtropical to tropical.

In the Amazon Basin of Brazil, a seasonally whitewater-flooded forest is known as a várzea, which is similar to igapó in many regards; the key difference between the two habitats is in the type of water that floods the forest.

Marantaceae

The Marantaceae are a family, the arrowroot family, of flowering plants known for its large starchy rhizomes. It is sometimes called the prayer-plant family. Combined morphological and DNA phylogenetic analyses indicate the family originated in Africa, although this is not the center of its extant diversity.

Myrmecochory

Myrmecochory ( (sometimes myrmechory); from Ancient Greek: μύρμηξ, romanized: mýrmēks and χορεία khoreíā "circular dance") is seed dispersal by ants, an ecologically significant ant-plant interaction with worldwide distribution. Most myrmecochorous plants produce seeds with elaiosomes, a term encompassing various external appendages or "food bodies" rich in lipids, amino acid, or other nutrients that are attractive to ants. The seed with its attached elaiosome is collectively known as a diaspore. Seed dispersal by ants is typically accomplished when foraging workers carry diaspores back to the ant colony after which the elaiosome is removed or fed directly to ant larvae. Once the elaiosome is consumed the seed is usually discarded in underground middens or ejected from the nest. Although diaspores are seldom distributed far from the parent plant, myrmecochores also benefit from this predominantly mutualistic interaction through dispersal to favourable locations for germination as well as escape from seed predation.

Parasitic plant

A parasitic plant is a plant that derives some or all of its nutritional requirement from another living plant. They make up about 1% of angiosperms and are in almost every biome in the world. All parasitic plants have modified roots, called haustoria, which penetrate the host plants, connecting them to the conductive system – either the xylem, the phloem, or both. For example, plants like Striga or Rhinanthus connect only to the xylem, via xylem bridges (xylem-feeding). Alternately, plants like Cuscuta and Orobanche connect only to the phloem of the host (phloem-feeding). This provides them with the ability to extract water and nutrients from the host. Parasitic plants are classified depending on where the parasitic plant latches onto the host and the amount of nutrients it requires. Some parasitic plants are able to locate their host plants by detecting chemicals in the air or soil given off by host shoots or roots, respectively. About 4,500 species of parasitic plant in approximately 20 families of flowering plants are known.

Pinophyta

The Pinophyta, also known as Coniferophyta or Coniferae, or commonly as conifers, are a division of vascular land plants containing a single extant class, Pinopsida. They are gymnosperms, cone-bearing seed plants. All extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs. Examples include cedars, Douglas firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 1998, the division Pinophyta was estimated to contain eight families, 68 genera, and 629 living species.Although the total number of species is relatively small, conifers are ecologically important. They are the dominant plants over large areas of land, most notably the taiga of the Northern Hemisphere, but also in similar cool climates in mountains further south. Boreal conifers have many wintertime adaptations. The narrow conical shape of northern conifers, and their downward-drooping limbs, help them shed snow. Many of them seasonally alter their biochemistry to make them more resistant to freezing. While tropical rainforests have more biodiversity and turnover, the immense conifer forests of the world represent the largest terrestrial carbon sink. Conifers are of great economic value for softwood lumber and paper production.

Seed dispersal syndrome

A seed dispersal syndrome is a mutualistic plant-animal interaction. Seed dispersal syndromes are morphological characters of seeds correlated to particular seed dispersal agents. Dispersal is the event by which individuals move from the site of their parents to establish in a new area. A seed disperser is the vector by which a seed moves from its parent to the resting place where the individual will establish, for instance an animal. Similar to the term syndrome, a diaspore is a morphological functional unit of a seed for dispersal purposes.Characteristics for seed dispersal syndromes are commonly fruit colour, mass, and persistence. These syndrome characteristics are often associated with the fruit that carries the seeds. Fruits are packages for seeds, composed of nutritious tissues to feed animals. However, fruit pulp is not commonly used as a seed dispersal syndrome because pulp nutritional value does not enhance seed dispersal success. Animals interact with these fruits because they are a common food source for them. Although, not all seed dispersal syndromes have fruits because not all seeds are dispersed by animals. Suitable biological and environmental conditions of dispersal syndromes are needed for seed dispersal and invasion success such as temperature and moisture.

Seed dispersal syndromes are parallel to pollination syndromes, which are defined as floral characteristics that attract organisms as pollinators. They are considered parallels because they are both plant-animal interactions, which increase the reproductive success of a plant. However, seed dispersal syndromes are more common in gymnosperms, while pollination syndromes are found in angiosperms.

Seeds disperse to increase the reproductive success of the plant. The farther away a seed is from a parent, the better its chances of survival and germination. Therefore, a plant should select certain traits to increase dispersal by a vector (i.e. bird) to increase the reproductive success of the plant.

Seed predation

Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source, in many cases leaving the seeds damaged and not viable. Granivores are found across many families of vertebrates (especially mammals and birds) as well as invertebrates (mainly insects); thus, seed predation occurs in virtually all terrestrial ecosystems. Seed predation is commonly divided into two distinctive temporal categories, pre-dispersal and post-dispersal predation, which affect the fitness of the parental plant and the dispersed offspring (the seed), respectively. Mitigating pre- and post-dispersal predation may involve different strategies. To counter seed predation, plants have evolved both physical defenses (e.g. shape and toughness of the seed coat) and chemical defenses (secondary compounds such as tannins and alkaloids). However, as plants have evolved seed defenses, seed predators have adapted to plant defenses (e.g., ability to detoxify chemical compounds). Thus, many interesting examples of coevolution arise from this dynamic relationship.

Seed trap

Seed traps are used in ecology and forestry to capture seeds falling from plants, allowing seed production and

dispersal to be quantified. They come in several forms, including funnel traps, sticky traps (using materials such as fly paper), nets and pots exposed in the field.

White-cheeked spider monkey

The white-cheeked spider monkey (Ateles marginatus) is a species of spider monkey, a type of New World monkey, endemic to Brazil. It moves around the forest canopy in small family groups of two to four, part of larger groups of a few dozen animals. This monkey feeds on leaves, flowers, fruits, bark, honey and small insects, and it is an important means of seed dispersal for forest trees. Females give birth after a 230-day gestation period. The population of this monkey is decreasing as its forest habitat is lost to soybean production, deforestation and road construction. It is also regarded as a delicacy and hunted for food. For these reasons, the International Union for Conservation of Nature has assessed the animal's conservation status as being "endangered".

White-eared opossum

The white-eared opossum (Didelphis albiventris) is an opossum species found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay. It is a terrestrial and, sometimes, arboreal animal, and a habitat generalist, living in a wide range of different habitats.For some time, this species was incorrectly known by the name D. azarae, correctly applied to the big-eared opossum. This led to azarae's discontinuation as a species name. From 1993 until 2002, this species also included the Guianan white-eared opossum (D. imperfecta) and the Andean white-eared opossum (D. pernigra) as subspecies.It is the team mascot of Clube Náutico Capibaribe, a Brazilian football team from Recife, Pernambuco.

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