Page 93 [93]
OCR
§ The limits of animal communities. The concept of supersocion | 91 coexistence must occur within tighter borders? Do we not end up identifying the animal association of a given space with the presocium? Coexistence is, indeed, relative, and the higher category we ascribe to coexistence, the hazier it becomes, though without doubt being a real occurrence. Every catena would coexist if there were no resource conflicts between catenaria, nor resource conflicts among presocia. Often, there is no direct link between populations in the different catenae. Between the populations of Baryscapus (Tetrastichus) diaphantus (terminalis) that belong to the Ceutorrhynchitena maculae-albae catena, and those of Halticoptera aenea, that is a member of the Oscinellaetena frit catena, there is only coexistence, even though they live alongside each other. Another population of T. terminalis, however, is an obstant element of the Eurybiatena cardui catena. Consequently, while Eurybia cardui and C. macula-alba populations can, at most, live in close spatial proximity, the adults of B. diaphanthus can form a community with both and, what is more, they also need this double connection, because during the second half of the summer, when both the poppies and wild poppies disappear, their winter larval cohort can only survive in the oecus provided by Centaurea sadleriana or Cirsium arvense. The adults of T. terminalis do not belong to either catena, and they are not obstants either but flower visitors, and probably sustinents. As such, they are members of the presocium! The larval population of Agrotis segetum (segetis) belongs to a presocium, as it can fit into several oecuses. Populations of its parasite, the braconid Periscepsia (Wagneria) carbonaria (migrans), can only have a coexistential relationship with any member of the Oscinellaetena frit catenarium, but the activity of Agrotis segetum can be fatal to populations of Oscinella frit and, if it destroys them, this action has a direct effect on all obstant elements of the Oscinellaetena frit catenarium. This link is, nonetheless, of a different nature to the case of Baryscapus (Tetrastichus) diaphantus (terminalis) shown above. In the former case, an obstant population changes into a presocium while, in the latter, a corrumpent element of a presocium clashes with a whole catena. Both are community relationships but at very different levels. Therefore we must distinguish the population interactions, and we can do this as follows: A coenotic relationship can be of four types: 1.) Bilateral, direct coenotic relationships exist among populations that mutually influence each other’s density, thus belonging to the same chain of energy exchange. Such a relationship exists between corrumpent (also sustinent, or herbivorous intercalary) and obstant elements of the same catenarium (compare Jermy’s (1956) connexulus). 2.) Unilateral, direct coenotic relationships exist between populations that are connected by the same energy transfer chain, but the influence on population density is unilateral. Such connections exist between the intercalary elements feeding on animal waste and the other populations (Jermy’s secunder connexulus).
