Inecology, abiological interaction is the effect that a pair oforganisms living together in acommunity have on each other. They can be either of the samespecies (intraspecific interactions), or of different species (interspecific interactions). These effects may be short-term, or long-term, both often strongly influence theadaptation andevolution of the species involved. Biological interactions range frommutualism, beneficial to both partners, tocompetition, harmful to both partners. Interactions can be direct when physical contact is established or indirect, through intermediaries such as shared resources, territories, ecological services, metabolic waste, toxins or growth inhibitors. This type of relationship can be shown by net effect based on individual effects on both organisms arising out of relationship.
Several recent studies have suggested non-trophic species interactions such as habitat modification and mutualisms can be important determinants of food web structures. However, it remains unclear whether these findings generalize across ecosystems, and whether non-trophic interactions affect food webs randomly, or affect specific trophic levels or functional groups.
Although biological interactions, more or less individually, were studied earlier,Edward Haskell (1949) gave an integrative approach to the thematic, proposing a classification of "co-actions",[1] later adopted by biologists as "interactions". Close and long-term interactions are described assymbiosis;[a] symbioses that are mutually beneficial are calledmutualistic.[2][3][4]
The term symbiosis was subject to a century-long debate about whether it should specifically denote mutualism, as inlichens or in parasites that benefit themselves.[5] This debate created two different classifications for biotic interactions, one based on the time (long-term and short-term interactions), and other based on the magnitude of interaction force (competition/mutualism) or effect of individual fitness, according thestress gradient hypothesis andMutualism Parasitism Continuum.Evolutionary game theory such asRed Queen Hypothesis,Red King Hypothesis orBlack Queen Hypothesis, have demonstrated a classification based on the force of interaction is important.[citation needed]
Predation is a short-term interaction, in which the predator, here anosprey, kills and eats its prey.
Short-term interactions, includingpredation andpollination, are extremely important inecology andevolution. These are short-lived in terms of the duration of a single interaction: a predator kills and eats a prey; a pollinator transfers pollen from one flower to another; but they are extremely durable in terms of their influence on the evolution of both partners. As a result, the partnerscoevolve.[6][7]
In predation, one organism, the predator, kills and eats another organism, its prey. Predators are adapted and often highly specialized for hunting, with acute senses such asvision,hearing, orsmell. Many predatory animals, bothvertebrate andinvertebrate, have sharpclaws orjaws to grip, kill, and cut up their prey. Other adaptations include stealth andaggressive mimicry that improve hunting efficiency. Predation has a powerfulselective effect on prey, causing them to developantipredator adaptations such aswarning coloration,alarm calls and othersignals,camouflage and defensive spines and chemicals.[8][9][10] Predation has been a major driver of evolution since at least theCambrian period.[6]
In pollination, pollinators includinginsects (entomophily), somebirds (ornithophily), and somebats, transferpollen from a male flower part to a female flower part, enablingfertilisation, in return for a reward of pollen or nectar.[11] The partners have coevolved through geological time; in the case of insects andflowering plants, the coevolution has continued for over 100 million years. Insect-pollinated flowers areadapted with shaped structures, bright colours, patterns, scent, nectar, and sticky pollen to attract insects, guide them to pick up and deposit pollen, and reward them for the service. Pollinator insects likebees are adapted to detect flowers by colour, pattern, and scent, to collect and transport pollen (such as with bristles shaped to form pollen baskets on their hind legs), and to collect and process nectar (in the case ofhoney bees, making and storinghoney). The adaptations on each side of the interaction match the adaptations on the other side, and have been shaped bynatural selection on their effectiveness of pollination.[7][12][13]
Seed dispersal is the movement, spread or transport ofseeds away from the parent plant. Plants have limited mobility and rely upon a variety ofdispersal vectors to transport their propagules, including bothabiotic vectors such as the wind and living (biotic) vectors like birds.[14] 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 areserotinous and only disperse their seeds in response to an environmental stimulus. Dispersal involves the letting go or detachment of a diaspore from the main parent plant.[15]
The six possible types ofsymbiosis are mutualism, commensalism, parasitism, neutralism, amensalism, and competition.[16] These are distinguished by the degree of benefit or harm they cause to each partner.[17]
Mutualism is an interaction between two or more species, where species derive a mutual benefit, for example an increasedcarrying capacity. Similar interactions within a species are known asco-operation. Mutualism may be classified in terms of the closeness of association, the closest being symbiosis, which is often confused with mutualism. One or both species involved in the interaction may beobligate, meaning they cannot survive in the short or long term without the other species. Though mutualism has historically received less attention than other interactions such as predation,[18] it is an important subject in ecology. Examples includecleaning symbiosis,gut flora,Müllerian mimicry, andnitrogen fixation by bacteria in the root nodules oflegumes.[citation needed]
Commensalism benefits one organism and the other organism is neither benefited nor harmed. It occurs when one organism takes benefits by interacting with another organism by which the host organism is not affected. A good example is aremora living with amanatee. Remoras feed on the manatee's faeces. The manatee is not affected by this interaction, as the remora does not deplete the manatee's resources.[19]
Parasitism is a relationship between species, where one organism, theparasite, lives on or in another organism, thehost, causing it some harm, and isadapted structurally to this way of life.[20] The parasite either feeds on the host, or, in the case of intestinal parasites, consumes some of its food.[21]
Neutralism (a term introduced byEugene Odum)[22] describes the relationship between two species that interact but do not affect each other. Examples of true neutralism are virtually impossible to prove; the term is in practice used to describe situations where interactions are negligible or insignificant.[23][24]
Leaf litter from these eucalypts contains chemicals which inhibit grass growth near the trees
Amensalism (a term introduced byEdward Haskell)[25] is an interaction where an organism inflicts harm to another organism without any costs or benefits received by itself.[26] This unidirectional process can be based on the release of one or more chemical compounds by one organism that negatively affect another, calledallelopathy.[27] One example of this is the microbial production of antibiotics that can inhibit or kill other, susceptible microorganisms. Another example is leaf litter from trees such asPinus ponderosa[28] orEucalyptus spp.[29] preventing the establishment and growth of other plant species.
A clear case of amensalism is wherehoofed mammals trample grass. Whilst the presence of the grass causes negligible detrimental effects to the animal's hoof, the grass suffers from being crushed. Amensalism also includes strongly asymmetrical competitive interactions, such as has been observed between the Spanishibex andweevils of the genusTimarcha, which both 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 eat the shrub and incidentally ingest the weevils.[30]
Competition can be defined as an interaction betweenorganisms or species, in which thefitness of one is lowered by the presence of another. Competition is often for a resource such asfood,water, orterritory inlimited supply, or for access to females for reproduction.[18] Competition among members of the same species is known asintraspecific competition, while competition between individuals of different species is known asinterspecific competition. According to thecompetitive exclusion principle, species less suited to compete for resources should eitheradapt ordie out.[31][32] This competition within and between species for resources plays a critical role innatural selection.[33]
Biotic interactions can vary in intensity (strength of interaction), and frequency (number of interactions in a given time).[34][35] There are direct interactions when there is a physical contact between individuals or indirect interactions when there is no physical contact, that is, the interaction occurs with a resource, ecological service, toxine or growth inhibitor.[36] The interactions can be directly determined by individuals (incidentally) or by stochastic processes (accidentally), for instance side effects that one individual have on other.[37] They are divided into six major types: Competition, Antagonism, Amensalism, Neutralism, Commensalism and Mutualism.[38]
Some examples of non-trophic interactions are habitat modification, mutualism and competition for space. It has been suggested recently that non-trophic interactions can indirectly affectfood web topology andtrophic dynamics by affecting the species in the network and the strength of trophic links.[39][40][41] It is necessary to integrate trophic and non-trophic interactions in ecological network analyses.[41][42][43] The few empirical studies that address this suggest food web structures (network topologies) can be strongly influenced by species interactions outside the trophic network.[39][40][44] However these studies include only a limited number of coastal systems, and it remains unclear to what extent these findings can be generalized. Whether non-trophic interactions typically affect specific species, trophic levels, or functional groups within the food web, or, alternatively, indiscriminately mediate species and their trophic interactions throughout the network has yet to be resolved.sessile species with generally low trophic levels seem to benefit more than others from non-trophic facilitation,[45] though facilitation benefits higher trophic and more mobile species as well.[44][46][47][48]
^abBegon, M., J.L. Harper and C.R. Townsend. 1996.Ecology: individuals, populations, and communities, Third Edition. Blackwell Science, Cambridge, Massachusetts.
^Gómez, José M.; González-Megías, Adela (2002). "Asymmetrical interactions between ungulates and phytophagous insects: Being different matters".Ecology.83 (1):203–11.doi:10.1890/0012-9658(2002)083[0203:AIBUAP]2.0.CO;2.
^Angelini, Christine; Silliman, Brian R. (January 2014). "Secondary foundation species as drivers of trophic and functional diversity: evidence from a tree-epiphyte system".Ecology.95 (1):185–196.Bibcode:2014Ecol...95..185A.doi:10.1890/13-0496.1.PMID24649658.
