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§ Ouantitative characteristics | 143
The question of dispersion also raises the concept of homogeneity in
zoocoenoses. What can we call a “homogeneous” zoocoenosis?
In phytocoenology, an association is considered homogeneous where the
characteristics of the individual constituent species are approximately similar
in the different quadrats. Can we transfer this criterion to zoocoenoses as
well? In our opinion, this cannot be done because, in a phytocoenosis, the
quantitative relations remain unchanged for a long period, but not so in
zoocoenoses which are in constant flux. Quantitative relationships in a
phytocoenosis indicate structure, but not so in zoocoenoses, where coeti are
the structural elements, which can be filled by the most varied populations.
It is impossible to talk about homogeneity in zoocoenoses based on the
similarity of structural elements and, probably, no zoocoenosis can be declared
homogeneous on the basis of its quantitative structure. Thus, we are left with
a group of qualitative parameters that we must examine. From a qualitative
point of view, we can consider a zoocoenosis homogeneous where it has the
same species representations in its whole area of distribution. We can assume
that such a zoocoenosis exists, even if it still has to be found. We can imagine
a Ceutorrhyachitena maculae-albae composed of the same populations in a
whole oak forest. We can, however, imagine the opposite, too: a zoocoenosis
is heterogeneous when certain groups of populations appear only at certain
points of its area of distribution, in an island-like manner; the species
representation is richer at some points than in others, constituting different
phases of the same zoocoenosis over a continuous area.
In defining homogeneity this way, we deviate from Balogh’s (1953)
viewpoint, who claims that “homogeneity in zoocoenoses is largely a matter
of area” (Balogh 1953: 55). This contradiction arises because Balogh uses
quantitative characteristics as criteria, while we consider a zoocoenosis
homo-, or heterogeneous, based only on qualitative characteristics. This is
in strict contradiction to Balogh, because we think that homogeneity is the
more probable when the area is smaller and, with an increasing area, the
formation of heterogeneity is more and more likely. Linking heterogeneity
and dispersion is not useful, because the uneven distribution of populations
remains, even across large areas.
There remains the question of how to evaluate different degrees of
dispersion? This is not an easy question, because dispersion also depends on
special features of population groups, thus its origins are idiobiological, and
can only be considered a coenological characteristic, because the type of
dispersion can influence the formation of a zoocoenosis.
Thalenhorst (1951) identified three types of horizontal dispersion for a
species, which can be accepted and extended to the whole zoocoenosis.
Dispersion can be:
1) continuous, when the constituent populations of the zoocoenosis are
represented by semaphoronts over the whole area (in every sample unit)
where the zoocoenosis is present;