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OCR
82 | IV. Categories of animal associations far away, descending on the populations of Moroccan locusts on the salty grassland. The trophic chain is more extensive in space, and will become more of a network, when the populations of more mobile and larger sized animals are considered (Elton’s (1927) “pyramid of numbers”). We are less interested, though, in the flow of energy along the trophic chains and networks, than the associations forced together by such trophic relationships. From the examples above, it can be seen that the trophic chain contains a group of populations that stays together, forming a “real” association. Such populations are the stable elements of the catena, forming the catena sensu stricto, and we can always find these together. The members that are attached only rarely and temporarily are often represented by single semaphoronts but, until they are present, they are not real members of the catena, and if they are obstants, one cannot deny that they possibly play a decisive role in the fate of populations belonging to that catena. Due to their short activity, though, they cannot be permanent members of the catena; therefore, they constitute the temporary elements of the food chain. Such temporary elements are obstant or intercalary populations and, for them, the catena in question is not the sole energy source; they move far and wide, and form temporary associations now here, now there. We shall soon see that these populations, that are usually dispersed over a large area, belong to the next, bigger associational category, and this includes the example above of the starlings. The stable elements of the catena are held together by a tight trophic chainlike connection. The catena is a real frame of an association, and its composition has to be unearthed using specific methods, and it is not identical to the species list of parasites and episites that make their appearance at the end of monographies devoted to pests as a list of natural enemies. Populations of the same species are always the starting point of all catenae; we see no obstacle to use this in nomenclature, emphasising that, in this case, a species name denotes an animal association. This is also practical, as it simplifies the discussion, if — as will be seen soon - the catena can be referred to by a single species name. We can also be certain that the same catena, the trophic chains originating from populations of the same species, will, according to the landscape differences, show different species combinations. If the catena bears the same name, we can also refer to these species combinations using a few qualifiers (as in plant sociology: Festucetum pseudovinae artemisetosum), and this means that from no less than a single name, we can draw conclusions about the landscape, biotope, or the presence of other catenae, etc. Therefore, we propose that, following the example of plant sociology, a special terminology is also introduced into zoocoenology, one that conforms to its needs, and promotes research as well as the better understanding of relationships.
