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80 | IV. Categories of animal associations § THE SMALLEST CATEGORY OF A ZOOCOENOSIS: THE CATENA From the statement on the structural elements of animal associations, it follows, naturally, that their formation is gradual, small at initiation and then expanding as they develop. Where should we look for the smallest units of a zoocoenosis? Given that the most important energy source is the plant cover, the simplest zoocoenoses should be sought here, at the meeting point of animals directly feeding on plants, and of zoophagous organisms. The more specialised a plant-transforming population is for its energy source, the more restricted will be the zoocoenosis forming around it, both in space and in its relation to energy sources. This is the simplest unit of an association, the smallest unit ofa zoocoenosis, the catena. A monophagous corrumpent, sustinent or intercalary population belongs to a catena, and its existentially dependent obstant, and possibly waste-consuming intercalary populations follow. The catena is, therefore, a trophic chain‘, in which the subsequent trophic levels are represented by the appropriate structural elements. One should not view a catena through an idiobiological lens, and be baffled that the same species may be present in various catenae; this view considers the species, but a zoocoenosis can only be viewed through a community lens. Looking at the question with this approach, it becomes clear that an obstant population living in a given catena (even if its species is polyphagous) is really existing in this catena - this trophic chain - and it is not possible that it can be present at the same time in any other place. The circumstance that other populations belonging to the same species live in other catenae means nothing more than that it will appear in the species combination of those catenae as well. The same occurs when an episitic semaphoront, during its hunting trips, will take prey from several catenae; the moment when it effectively entered that catena, it became its full member. This view is not only more correct coenologically, but is also of theoretical importance, because the various populations of the same species, when they are active in several catenae, form coenological links between these small zoocoenological categories. It is certain that several parasitic or episitic obstant elements that depend on several hosts can only remain in the zoocoenosis if these hosts are present there. These cannot be members of the same catena and, due to their intermediary host needs, can only fit into catena A if catenae Band C are also present. The relative obscurity of obstants, compared to the + For these links, we use this term instead of the food chain, which has a production biological “nuance’, emphasising the distance kept from any production-biological approach or influence. By food chain we mean the path through which the energy-binding organic material progresses through the animal elements, while a trophic chain is the mutual dependence of populations that are forced into a zoocoenosis because of their trophic dependence. We believe such a sharp distinction is useful.
