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§ 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).