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72 | III. Biotope and animal associations
trophic relations, but the divergent ecological factors following from the
oecus-structure of the biotopes. Similar differences are reported by Kuehnelt
(1950:251) who demonstrated microclimatic variances between neighbouring
tree stumps, and whose zoocoenoses, consequently, reflected these differences.
The oecus, above all, must be seen as an energy source of special quality, even
though a manifestation of defined environmental conditions; the first
characteristic may be of decisive importance for colonising populations. The
same oecus can therefore harbour different zoocoenoses.
To complete our understanding, we have to examine one further
circumstance. When several plant species form a characteristic plant association,
this also results in groups of oecuses, showing structure-related features that
influence the microclimate. Such a sub-biotope (see Varga, in Fehér et al.,
1954) is the ecotone; in the arvideserta, the crop plus its weeds and in an
agrilinosa, the fruit trees and the weeds growing among them. The structure
of the biotope follows from the grouping of the oecus, and changes in the
microclimatic relations that are influenced by this structure, while the essence
of the energy source remains unchanged. The same oak species will represent
the same energy source everywhere, but will be available under various
microclimatic conditions in a gallery forest vs. a forest of closed canopy. The
animals do not only need food, but a certain combination of macro- and
microclimatic conditions and, only when these are available, can they utilise
the food source. The influence of soil moisture can be illustrated well by the
behaviour of Nicrophorus (Necrophorus) populations: on moist, clay forest
soils, N. humator; on dry, sandy soils N. vespilloides and; on meadows, N.
vespillo populations will live on the same food source (Pukowski, 1953).
A few more words on the concept of the statio, that is also needed in
zoocoenology, because we separate the various animal populations by their
species identity. To survive in a zoocoenosis, a population needs to find the
conditions that it can tolerate as an inherited feature of its species. As a
population of a species is a member of an animal association, so do all
populations belong to a species. The statio is a spatial expression of the
species-specific need concerning the living and non-living elements of its
environment. This need can be modified by evolutionary adaptations, but
such needs are always present. The realised zoocoenosis of a given biotope,
or oecus, also depends on the statio needs of the populations of the species
present. At this point, the syn- and idiobiological viewpoints must meet even
though they must not be mixed, because the latter helps to better understand
the formation of the association under study. With better description of
animal associations and zoocoenoses, more light will be shed onto the
ecological needs of the participating species, thus increasing our idiobiological
knowledge about them. This illustrates why, in zoocoenology, we need to
pay attention to the idiobiological concept of statio that mirrors the species¬
specific needs. The law of changing stadia (Bej-Bienko, see Tschegolev, 1951;
Bej-Bienko and Mishtschenko, 1951; see also Elton, 1927; Kühnelt, 1943;