Symbiosis ( Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biological interaction, between two organisms of different species. The two organisms, termed symbionts, can be either in a mutualistic, a commensalistic, or a parasitic relationship. In 1879, Heinrich Anton de Bary defined symbiosis as "the living together of unlike organisms". The term is sometimes more exclusively used in a restricted, mutualistic sense, where both symbionts contribute to each other's subsistence. Symbiosis can be ''obligatory'', which means that one, or both of the symbionts depend on each other for survival, or ''facultative'' (optional), when they can also subsist independently. Symbiosis is also classified by physical attachment. Symbionts forming a single body live in ''conjunctive'' symbiosis, while all other arrangements are called ''disjunctive'' symbiosis."Symbiosis". Dorland's Illustrated Medical Dictionary. Philadelphia: Elsevier Health Sciences, 2007. Credo Reference. Web. 17 September 2012 When one organism lives on the surface of another, such as head lice on humans, it is called ectosymbiosis; when one partner lives inside the tissues of another, such as '' Symbiodinium'' within coral, it is termed endosymbiosis.

Definition

The definition of ''symbiosis'' was a matter of debate for 130 years. In 1877, Albert Bernhard Frank used the term ''symbiosis'' to describe the mutualistic relationship in

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Heinrich Anton de Bary defined it as "the living together of unlike organisms". The definition has varied among scientists, with some advocating that it should only refer to persistent mutualisms, while others thought it should apply to all persistent biological interactions (in other words, to mutualism, commensalism, and

parasitism 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 ...

, but excluding brief interactions such as predation). In the 21st century, the latter has become the definition widely accepted by biologists. In 1949, Edward Haskell proposed an integrative approach with a classification of "co-actions", later adopted by biologists as "interactions".

Types

Obligate versus facultative

Relationships can be obligate, meaning that one or both of the symbionts entirely depend on each other for survival. For example, in

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

symbionts, the fungal partners cannot live on their own. The algal or cyanobacterial symbionts in lichens, such as '' Trentepohlia'', can generally live independently, and their part of the relationship is therefore described as facultative (optional), or non-obligate. When one of the participants in a symbiotic relationship is capable of photosynthesis, as with lichens, it is called photosymbiosis.

Ectosymbiosis versus endosymbiosis

Ectosymbiosis is any symbiotic relationship in which the symbiont lives on the body surface of the

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

, including the inner surface of the digestive tract or the ducts of exocrine glands. Examples of this include ectoparasites such as

lice Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result o ...

; commensal ectosymbionts such as the barnacles, which attach themselves to the jaw of baleen whales; and mutualist ectosymbionts such as cleaner fish. Contrastingly, endosymbiosis is any symbiotic relationship in which one symbiont lives within the tissues of the other, either within the cells or extracellularly. Examples include diverse microbiomes:

rhizobia Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In gene ...

, nitrogen-fixing bacteria that live in

root nodules Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known a ...

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...

roots; actinomycetes, nitrogen-fixing bacteria such as '' Frankia'', which live in alder root nodules; single-celled

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

inside reef-building corals; and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects. In endosymbiosis, the host cell lacks some of the nutrients which the endosymbiont provides. As a result, the host favors endosymbiont's growth processes within itself by producing some specialized cells. These cells affect the genetic composition of the host in order to regulate the increasing population of the endosymbionts and ensure that these genetic changes are passed onto the offspring via

vertical transmission Vertical transmission of symbionts is the transfer of a microbial symbiont from the parent directly to the offspring. Many metazoan species carry symbiotic bacteria which play a mutualistic, commensal, or parasitic role. A symbiont is acquire ...

(

heredity Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inform ...

). As the endosymbiont adapts to the host's lifestyle, the endosymbiont changes dramatically. There is a drastic reduction in its genome size, as many genes are lost during the process of metabolism, and DNA repair and recombination, while important genes participating in the DNA-to-RNA

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

, protein translation and DNA/RNA replication are retained. The decrease in genome size is due to loss of protein coding genes and not due to lessening of inter-genic regions or open reading frame (ORF) size. Species that are naturally evolving and contain reduced sizes of genes can be accounted for an increased number of noticeable differences between them, thereby leading to changes in their evolutionary rates. When endosymbiotic bacteria related with insects are passed on to the offspring strictly via vertical genetic transmission, intracellular bacteria go across many hurdles during the process, resulting in the decrease in effective population sizes, as compared to the free-living bacteria. The incapability of the endosymbiotic bacteria to reinstate their wild type phenotype via a recombination process is called '' Muller's ratchet'' phenomenon. Muller's ratchet phenomenon, together with less effective population sizes, leads to an accretion of deleterious mutations in the non-essential genes of the intracellular bacteria. This can be due to lack of selection mechanisms prevailing in the relatively "rich" host environment.

Competition

Competition can be defined as an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource (such as

food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...

, water, and territory) used by both usually facilitates this type of interaction, although the competition can also be for other resources.Begon, M.; Harper, J.L.; Townsend, C.R. 1996. ''Ecology: individuals, populations, and communities'', Third Edition. Blackwell, Cambridge, Massachusetts. Chapters 5 "Intraspecific Competition" and 8 "Interspecific Competition"

Amensalism

Amensalism is a non-symbiotic, asymmetric interaction where one species is harmed or killed by the other, and one is unaffected by the other. There are two types of amensalism, competition and

antagonism Antagonism may refer to: *The characteristic of an antagonist *Antagonism (chemistry), where the involvement of multiple agents reduces their overall effect *Receptor antagonist or pharmacological antagonist, a substance that binds to the site an ...

(or antibiosis). Competition is where a larger or stronger organism deprives a smaller or weaker one of a resource. Antagonism occurs when one organism is damaged or killed by another through a chemical secretion. An example of competition is a sapling growing under the shadow of a mature tree. The mature tree can rob the sapling of necessary sunlight and, if the mature tree is very large, it can take up rainwater and deplete soil nutrients. Throughout the process, the mature tree is unaffected by the sapling. Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling. An example of antagonism is '' Juglans nigra'' (black walnut), secreting juglone, a substance which destroys many herbaceous plants within its root zone. The term ''amensalism'' is often used to describe strongly asymmetrical competitive interactions, such as between the Spanish ibex and

weevil Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...

s of the genus ''

Timarcha ''Timarcha'' is a genus of leaf beetles in the family Chrysomelidae, with more than 100 described species in three subgenera. The most widely known species is ''T. tenebricosa'', the bloody-nosed beetle. All species are black, wingless organisms ...

'' which feed upon the same type of shrub. Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it.

Commensalism

Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. It is derived from the English word commensal, used of human

social interaction A social relation or also described as a social interaction or social experience is the fundamental unit of analysis within the social sciences, and describes any voluntary or involuntary interpersonal relationship between two or more individuals ...

. It derives from a medieval Latin word meaning sharing food, formed from ''com-'' (with) and ''mensa'' (table). Commensal relationships may involve one organism using another for transportation ( phoresy) or for housing (

inquilinism In zoology, an inquiline (from Latin ''inquilinus'', "lodger" or "tenant") is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms such as insects may live in the h ...

), or it may also involve one organism using something another created, after its death (

metabiosis Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

). Examples of metabiosis are hermit crabs using

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

shells to protect their bodies, and spiders building their webs on plants.

Mutualism

Calcinus laevimanus hermit crab with Calliactis sea anemone

Mutualism or interspecies reciprocal altruism is a long-term relationship between individuals of different species where both individuals benefit. Mutualistic relationships may be either obligate for both species, obligate for one but facultative for the other, or facultative for both. Bryolith (Banc d'Arguin, Mauritania)

Many herbivores have mutualistic

gut flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut mi ...

to help them digest plant matter, which is more difficult to digest than animal prey. This gut flora comprises cellulose-digesting protozoans or bacteria living in the herbivores' intestines. Coral reefs result from mutualism between coral organisms and various algae living inside them. Most land plants and land ecosystems rely on mutualism between the plants, which

fix Fix or FIX may refer to: People with the name * Fix (surname) Arts, entertainment, and media Films * ''Fix'' (film), a feature film by Tao Ruspoli Music * ''Fix'' (album), 2015 album by Chris Lane * "Fix" (Blackstreet song), 1997 song by Black ...

carbon from the air, and

mycorrhyzal A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...

fungi, which help in extracting water and minerals from the ground. An example of mutualism is the relationship between the ocellaris clownfish that dwell among the tentacles of Ritteri sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn, the anemone stinging tentacles protect the clownfish from its predators. A special mucus on the clownfish protects it from the stinging tentacles. A further example is the goby, a fish which sometimes lives together with a

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

. The shrimp digs and cleans up a burrow in the sand in which both the shrimp and the goby fish live. The shrimp is almost blind, leaving it vulnerable to predators when outside its burrow. In case of danger, the goby touches the shrimp with its tail to warn it. When that happens both the shrimp and goby quickly retreat into the burrow. Different species of gobies ('' Elacatinus spp.'') also clean up ectoparasites in other fish, possibly another kind of mutualism. A spectacular example of obligate mutualism is the relationship between the

siboglinid Siboglinidae is a family of polychaete annelid worms whose members made up the former phyla Pogonophora and Vestimentifera (the giant tube worms). The family is composed of about 100 species of vermiform creatures which live in thin tubes buried ...

tube worms and symbiotic bacteria that live at

hydrothermal vents A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...

and cold seeps. The worm has no digestive tract and is wholly reliant on its internal symbionts for nutrition. The bacteria oxidize either

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

or methane, which the host supplies to them. These worms were discovered in the late 1980s at the hydrothermal vents near the Galapagos Islands and have since been found at deep-sea hydrothermal vents and cold seeps in all of the world's oceans. Mutualism improves both organism's competitive ability and will outcompete organisms of the same species that lack the symbiont. A facultative symbiosis is seen in encrusting bryozoans and

hermit crabs Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an a ...

. The bryozoan colony (''Acanthodesia commensale'') develops a cirumrotatory growth and offers the crab (''Pseudopagurus granulimanus'') a helicospiral-tubular extension of its living chamber that initially was situated within a gastropod shell.

Parasitism

Taenia solium tapeworm scolex with its four suckers and two rows of hooks 5262 lores

In a parasitic relationship, the parasite benefits while the host is harmed. Parasitism takes many forms, from

endoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

that live within the host's body to ectoparasites and

parasitic castrator Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part, to its own benefit. This is one of six major strategies within parasitism. Evolutionary strategy The parasitic castration strateg ...

s that live on its surface and

micropredator Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

s like mosquitoes that visit intermittently. Parasitism is an extremely successful mode of life; about 40% of all animal species are parasites, and the average mammal species is host to 4 nematodes, 2 cestodes, and 2 trematodes.

Mimicry

Mimicry is a form of symbiosis in which a species adopts distinct characteristics of another species to alter its relationship dynamic with the species being mimicked, to its own advantage. Among the many types of mimicry are Batesian and Müllerian, the first involving one-sided exploitation, the second providing mutual benefit.

Batesian mimicry Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, after his work on bu ...

is an exploitative three-party interaction where one species, the mimic, has evolved to mimic another, the model, to deceive a third, the dupe. In terms of signalling theory, the mimic and model have evolved to send a signal; the dupe has evolved to receive it from the model. This is to the advantage of the mimic but to the detriment of both the model, whose protective signals are effectively weakened, and of the dupe, which is deprived of an edible prey. For example, a wasp is a strongly-defended model, which signals with its conspicuous black and yellow coloration that it is an unprofitable prey to predators such as birds which hunt by sight; many hoverflies are Batesian mimics of wasps, and any bird that avoids these hoverflies is a dupe.; Reprint: In contrast, Müllerian mimicry is mutually beneficial as all participants are both models and mimics. For example, different species of bumblebee mimic each other, with similar warning coloration in combinations of black, white, red, and yellow, and all of them benefit from the relationship.

Cleaning symbiosis

Cleaning symbiosis Cleaning symbiosis is a mutually beneficial association between individuals of two species, where one (the cleaner) removes and eats parasites and other materials from the surface of the other (the client). Cleaning symbiosis is well-known amon ...

is an association between individuals of two species, where one (the cleaner) removes and eats parasites and other materials from the surface of the other (the client). It is putatively mutually beneficial, but biologists have long debated whether it is mutual selfishness, or simply exploitative. Cleaning symbiosis is well known among marine fish, where some small species of cleaner fish – notably

wrasse The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 81 genera, which are divided into 9 subgroups or tribes. They are typically small, most of them le ...

s, but also species in other genera – are specialized to feed almost exclusively by cleaning larger fish and other marine animals. In a supreme situation, the host species (fish or marine life) will display itself at a designated station deemed the "cleaning station". Cleaner fish play an essential role in the reduction of parasitism on marine animals. Some shark species participate in cleaning symbiosis, where cleaner fish remove ectoparasites from the body of the shark. A study by Raymond Keyes addresses the atypical behavior of a few shark species when exposed to cleaner fish. In this experiment, cleaner wrasse ''(Labroides dimidiatus)'' and various shark species were placed in a tank together and observed. The different shark species exhibited different responses and behaviors around the wrasse. For example, Atlantic and Pacific lemon sharks consistently react to the wrasse fish in a fascinating way. During the interaction, the shark remains passive and the wrasse swims to it. It begins to scan the shark's body, sometimes stopping to inspect specific areas. Commonly, the wrasse would inspect the gills, labial regions, and skin. When the wrasse makes its way to the mouth of the shark, the shark often ceases breathing for up to two and a half minutes so that the fish is able to scan the mouth. Then, the fish passes further into the mouth to examine the gills, specifically the buccopharyngeal area, which typically holds the most parasites. When the shark begins to close its mouth, the wrasse finishes its examination and goes elsewhere. Male bull sharks exhibit slightly different behavior at cleaning stations: as the shark swims into a colony of wrasse fish, it drastically slows its speed to allow the cleaners to do their job. After approximately one minute, the shark returns to normal swimming speed.

Role in evolution

Symbiosis is increasingly recognized as an important selective force behind evolution; many species have a long history of interdependent co-evolution. Although symbiosis was once discounted as an anecdotal evolutionary phenomenon, evidence is now overwhelming that obligate or facultative associations among microorganisms and between microorganisms and multicellular hosts had crucial consequences in many landmark events in evolution and in the generation of phenotypic diversity and complex phenotypes able to colonise new environments. CC-BY icon

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Hologenome development and evolution

Evolution originated from changes in development where variations within species are selected for or against because of the symbionts involved. The hologenome theory relates to the holobiont and symbionts genome together as a whole. Microbes live everywhere in and on every multicellular organism. Many organisms rely on their symbionts in order to develop properly, this is known as co-development. In cases of co-development the symbionts send signals to their host which determine developmental processes. Co-development is commonly seen in both arthropods and vertebrates.

Symbiogenesis

One hypothesis for the origin of the nucleus in

eukaryotes Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

(plants, animals, fungi, and

protists A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the excl ...

) is that it developed from a symbiogenesis between bacteria and archaea. It is hypothesized that the symbiosis originated when ancient archaea, similar to modern methanogenic archaea, invaded and lived within bacteria similar to modern myxobacteria, eventually forming the early nucleus. This theory is analogous to the accepted theory for the origin of eukaryotic mitochondria and chloroplasts, which are thought to have developed from a similar endosymbiotic relationship between proto-eukaryotes and aerobic bacteria. Evidence for this includes the fact that

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

and

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s divide independently of the cell, and that these organelles have their own genome. The biologist Lynn Margulis, famous for her work on endosymbiosis, contended that symbiosis is a major driving force behind evolution. She considered

Darwin Darwin may refer to: Common meanings * Charles Darwin (1809–1882), English naturalist and writer, best known as the originator of the theory of biological evolution by natural selection * Darwin, Northern Territory, a territorial capital city i ...

's notion of evolution, driven by competition, to be incomplete and claimed that evolution is strongly based on

co-operation Cooperation (written as co-operation in British English) is the process of groups of organisms working or acting together for common, mutual, or some underlying benefit, as opposed to working in competition for selfish benefit. Many animal a ...

, interaction, and

mutual dependence Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

among organisms. According to Margulis and her son

Dorion Sagan Dorion Sagan (born 1959) is an American essayist, fiction writer, poet, and theorist of ecology. He has written and co-authored books on culture, art, literature, evolution, and the history and philosophy of science, including ''Cosmic Apprentice, ...

, " Life did not take over the globe by

combat Combat ( French for ''fight'') is a purposeful violent conflict meant to physically harm or kill the opposition. Combat may be armed (using weapons) or unarmed ( not using weapons). Combat is sometimes resorted to as a method of self-defense, or ...

, but by

networking Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

Major examples of co-evolutionary relationships

Mycorrhiza

About 80% of vascular plants worldwide form symbiotic relationships with fungi, in particular in arbuscular mycorrhizas. Hummingbird hawkmoth a

Pollination

Flowering plants and the animals that pollinate them have co-evolved. Many plants that are pollinated by insects (in entomophily), bats, or birds (in ornithophily) have highly specialized flowers modified to promote pollination by a specific pollinator that is correspondingly adapted. The first flowering plants in the fossil record had relatively simple flowers. Adaptive

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

quickly gave rise to many diverse groups of plants, and, at the same time, corresponding speciation occurred in certain insect groups. Some groups of plants developed nectar and large sticky pollen, while insects evolved more specialized morphologies to access and collect these rich food sources. In some taxa of plants and insects, the relationship has become dependent, where the plant species can only be pollinated by one species of insect.

Acacia ants and acacias

The

acacia ant The acacia ant (''Pseudomyrmex ferruginea'') is a species of ant of the genus ''Pseudomyrmex''. These arboreal, wasp-like ants have an orange-brown body around 3 mm in length and very large eyes. The acacia ant is best known and named for ...

(''Pseudomyrmex ferruginea'') is an obligate plant ant that protects at least five species of "Acacia" (''

Vachellia ''Vachellia'' is a genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or acacias. It belongs to the subfamily Mimosoideae. Its species were considered members of genus ''Acacia'' until 2009. ''Vachellia'' can ...

'') from preying insects and from other plants competing for sunlight, and the tree provides nourishment and shelter for the ant and its larvae.

Seed dispersal

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 propagules, including both abiotic vectors such as the wind and living (

biotic Biotics describe living or once living components of a community; for example organisms, such as animals and plants. Biotic may refer to: *Life, the condition of living organisms *Biology, the study of life * Biotic material, which is derived from ...

) vectors like birds. In order to attract animals, these plants evolved a set of morphological characters such as fruit colour, mass, and persistence correlated to particular seed dispersal agents. For example, plants may evolve conspicuous fruit colours to attract avian frugivores, and birds may learn to associate such colours with a food resource.

Rhizobia

Lichens

Notes

References

Sources

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External links

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TED-Education video
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Symbiosis: a surprising tale of species cooperation
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Symbiosis Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

Ecology