Medvrstni odnosi krojijo strukturo življenskih združb: večvrstni interakcijski kompleksi v ekosistemih / Interspecific interactions are structuring natural assemblages: multispecies interaction complexes in ecosystems

author: Al Vrezec, Oddelek za raziskave organizmov in ekosistemov, Nacionalni inštitut za biologijo
produced by: Videofon d.o.o.
published: June 30, 2010,   recorded: October 2008,   views: 3456
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Medvrstna razmerja ali interakcije med vrstami so temeljno gibalo v oblikovanju združb, torej njihove vrstne sestave in abundance posameznih vrst v njej. Z razmerji razlagamo odnose med dvema vrstama, torej v kakšnem neposrednem odnosu sta vrsti v okolju. Z neposrednimi razmerji pa lahko le delno razložimo strukturo združb in ekosistemov, saj so nedavne raziskave pokazale na pomen posrednih razmerij v biokompleksnosti ekoloških sistemov. Neposredna razmerja razumemo kot interakcije med dvema vrstama, pri čemer zaradi delovanja ene vrste številčnost druge upada ali raste, pri posrednih razmerjih pa smo soočeni s sistemom treh ali več vrst. Pravzaprav gre za splet različnih neposrednih interakciji, v katerih dve vrsti, ki nista v neposrednem stiku, prek tretje posredniške vrste ali mediatorja vplivata druga na drugo. Najbolj preučena oblika posrednih interakcij je prikrita kompeticija, pri kateri je mediator vrsta, ki je navadno na višjem trofi čnem nivoju kot pa prikrita kompetitorja in je bodisi plenilec, parazit ali parazitoid. Populacija mediatorja se lahko povečuje zaradi alternativnega plena ali gostitelja, ki predstavlja prikritega kompetitorja vrsti, ki je glavni plen oziroma gostitelj mediatorja. Zaradi alternativnega plena se lahko povečuje število mediatorja, s tem pa se povečuje tudi predacijski pritisk oziroma verjetnost infekcije glavnega plena oziroma gostitelja. Proces lahko pripelje do popolne izključitve glavnega plena oziroma gostitelja iz sistema, populaciji mediatorja in alternativnega plena oziroma gostitelja pa se ujameta v ravnovesju. Do sedaj je bilo prepoznanih že več tipov prikrite kompeticije, ki predstavlja negativno razmerje med prikritima kompetitorjema, medtem ko je primerov pozitivnih posrednih razmerij do sedaj znanih zelo malo in jih opisujejo kot prikriti mutualizem. Poznavanje posrednih interakcij se je izkazalo kot zelo pomembno v agrarnih sistemih, zlasti kar se tiče zatiranja za kmetijstvo škodljivih žuželk. Veliko nevarnost pa predstavljajo tudi vnosi eksotov, ki lahko prek deljenega mediatorja povzročijo popolno izključitev in izumrtje avtohtonih vrst in naravnih ekosistemov.


Interspecific interactions are the fundamental motive for the formation of communities, that is of their species richness and species abundance. Interactions are used to explain the relations between two species. However, these direct relations can only partially explain the structure of communities and ecosystems. Recent studies have showed that indirect relations are important for the biocomplexity of ecosystems as well. Direct reationships are actually interspecific interactions where one species increases or decreases the quantity of the other species. In indirect relations three or more species are involved via direct interactions. Two species which are not directly connected are in the relations via the third species, the mediator and thus affect each other. The most investigated type of the indirect interactions is the hidden competition, where the mediator species is on higher tropical level as are the hidden competitors, and is a predator, parasite or parasitoid. The mediator population can increase due to alternative pray, causing the increase of the predation pressure or the increase of the possibility of pray’s or main host’s infection. The process can lead to the total exclution of the main pray or host from the system, but the populations of the mediator and the alternative pray are in the equlibrium. So far, several types of hidden competition were recognized, mostly negative. Only few positive interactions are known and are described as hidden mutualism. The knowledge on indirect interactions was found to be very important in agricultural systems, such as insect repellents. High risk for the environment is also the intoduction of foreign species, which can cause total elimination and extinction of native species and natural ecosystems because of the same mediator.

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