Oldal 145 [145]
OCR
§ 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;
