Trophic niche
The trophic niche (from the Greek τροφή trophé - "nutrition") refers to the component of food as part of the ecological niche . It describes the nutritional biology of the species in question, for example the food spectrum it uses and the related specializations.
definition
According to the concept of the ecological niche as a multi-dimensional space (according to GE Hutchinson), not only abiotic environmental factors such as temperature and precipitation but also resources such as food determine the long-term survival of a species in a habitat. A species can only colonize a habitat if it has usable food, e.g. B. prey organisms, is present here and its use by other species, z. B. food competitors, is denied.
In ecology , a distinction is therefore made between the fundamental niche (the possible existence in a habitat without considering interspecific competition ) and the realized niche , which takes into account the interactions of the species and which can therefore actually be used.
competitor
The competition for resources between different species ( interspecific competition ) can influence natural selection . A distinction is made between exploitation and interference. The former describes the indirect influence on another species through the use of the same resource and the associated reduced availability of this resource. In contrast, interference describes the direct exertion of influence, i.e. the obstruction of access to an existing resource (for example, through aggressive behavior towards competitors).
Resource sharing reduces the pressure of competition between different species. Nutrition specialists escape the pressure of competition by specializing in one resource. If, on the other hand, two species use the same resource, their ecological niches overlap (niche overlap), so that the choice of food can be restricted and the niche space is reduced. In reality, the competition is often asymmetrical. The realized niche of a highly competitive species corresponds much closer to its fundamental niche (physiologically possible) than that of a weakly competitive species.
The principle of exclusion of competition states that sooner or later one species will be displaced by the better adapted species if these two species have identical resource requirements. In real habitats, numerous species coexist that have similar or even almost identical resource requirements without always having to exclude competition. The reasons for this are very diverse and one of the central research fields of ecology. Obviously, however, species can almost always gain evolutionary advantages if - for example through special diets - the interspecific competitive pressure is reduced.
Nutrition specialists
As a dietary specialists are heterotrophic organisms that depend on a particular type, composition and type of food called. They usually only feed on one or very few resources. It is said that the specialists are mono- or oligophagous. In contrast, there are the generalists who eat polyphagously. Few species are perfect generalists. As a rule, they also have a food preference. So they prefer one component of their prey spectrum.
The trophic niche of a species does not only refer to the composition of the food, but also to the circumstances of the acquisition of food itself: animals eat different food at different times of the day or look for different places to forage or metabolize substances that cannot be used by other species .
Since the basic features of the nutritional requirements of the individual representatives of the animal kingdom are almost identical due to the same cellular metabolic pathways, specialization is less based on a different requirement for essential nutrients themselves, but on special ways of acquiring them. Important are e.g. B. Different equipment with digestive enzymes that can break down food that remains indigestible for others or that can render toxins and antibodies harmless. Adaptations to be able to use particularly well-protected, mobile or hidden prey are very important. These adaptations can be morphological (e.g. particularly strong teeth in order to be able to crack armored prey), or they can be based on innate behaviors that open up special food sources for the individual animal species. If this rigid behavior pattern is circumvented (e.g. by applying so-called phagostimulate to otherwise unaccepted food), there may be a change in food to other food sources. Nutrition specialists in the narrow sense sometimes only consume a single chemical compound (for example wax , keratin ) as food, whereby the activity of symbiotic intestinal microorganisms is often required to nourish the organism. The transition from food specialists in the main , who, depending on the habitat, predominantly develop a source of food or who specialize in the mechanical properties of food, to omnivores is fluid.
The specialization in a certain food is in many cases largely dependent on its availability, so that seasonal polyphagous animals can be temporary food specialists . The choice of certain nutrients is often mediated by smells and flavors .
Examples
- Xylophagia is the consumption of wood. Living things that feed on wood are mostly insects.
- Cellulomonas is a genus of bacteria that specializes in the decomposition of cellulose.
literature
- TM Smith, RL Smith: Ecology , Pearson Studies, 6th Edition 2009, ISBN 978-3-8273-7313-7
- Neil A. Campbell: Biology , Spectrum, Akademischer Verlag, Heidelberg and Berlin, 1st edition 1997, ISBN 9783827400321
- Eugene P. Odum: Fundamentals of Ecology . Thieme Verlag, Leipzig and Mannheim, 3rd edition, ISBN 3133823035
- H. Walletschek, J. Graw: Öko-Lexikon , Verlag CH Beck, Munich, 5th, neubearb. Edition, 1994, ISBN 3406385729
- Brockhaus Encyclopedia : Biosphere - The habitats of the earth . FA Brockhaus, Leipzig and Mannheim, Vol. 1, 2002, ISBN 3765311812
- Begon, M., Harper, JL, Townsend, CR: Ecology . Spektrum, Akademischer Verlag, 3rd edition, 1998, ISBN 3827402263