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§ Quantitative characteristics | 133
8. Dominance
Dominance (relative abundance) expresses the percentage of the abundance of
a given population in relation to the total abundance of all related populations
in the zoocoenosis.
In the definition, the emphasis is on the term “related” Given that
dominance is a relative characteristic, it is inconceivable that we compare
elements that have got nothing in common (Tischler, 1950; Kuehnelt, 1951;
Balogh, 1953); therefore, the preconditions for the correct interpretation of
dominance is that we employ it within an identified zoocoenosis and, even
within that, we compare only population groups whose trophic position
allows this comparison. It is peculiar that, in zoocoenological practice, the
literature is full of dominance values that were obtained by comparing all
species collected. The explanation is, clearly, that the fauna of the given area
was analysed, but not the zoocoenosis present and, not knowing the real role
of the populations found, no attempt is made to establish the species
combinations of the given zoocoenosis. Behind this procedure lurks the
thought that dominant species have the biggest role in a zoocoenosis, which
is not the correct starting point (Smith, 1928), because this projects something
that is still to be proven onto the zoocoenosis. In a zoocoenosis, there can
be small, rare but sharply delimited catenaria, where all constituent populations
have low abundance. If we determine dominance by projecting it onto a given
area, it can lead to us not even notice these catenaria, as their dominance
values will be far inferior than those of others that may play a minimal role
(for example, because they are in diapause), yet have high abundance.
By calculating dominance, one or more populations will be elevated above
others, therefore we must ask: how can we establish dominance within a
given zoocoenosis, and the dominance of which population should be
considered the outstanding characteristic of the studied category?
Without doubt, populations belonging to plant-dependent coeti must
show some surplus to serve as energy sources for obstant and intercalary
elements, and the same holds for higher trophic levels, too. Such a surplus
can be of three kinds: if semaphoronts of two populations, that are in a trophic
relationship, have largely similar mass and numbers, the surplus in the host
populations is indicated by higher numbers, and its dominance is clear and
unequivocal. If the semaphoront of the host population is significantly bigger
(in mass and size), it can support several, or many, individuals of a smaller
(by mass or size) obstant. In this case, the obstant element can be dominant
(by abundance) over the host population, while the latter is dominant by
mass. If the members of the obstant semaphoront are much bigger than the
host individuals, the prey population must be highly dominant, numerically,
so that only one-two semaphoront of the obstant will stand against an
overwhelmingly bigger population of the host, or (which seems to be more
common) the obstant has to relate to several, occasionally many, hosts.