Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 57. (Budapest 1965)
Agócsy, P.: The Mts. Pilis as a divide of the mollusk faunas in the Central Range, Hungary
The Mts. Pilis as a Divide of the Mollusk Faunas in the Central Range, Hungary By P. AGÓCSY, Budapest In the eyes of the malacologist, the Central Range is one of the most interesting areas of our country. The conditions of soil, climate vegetation had made possible there the evolvement and survival to this day of a rich and diversified mullosk fauna. The Central Range of Hungary is a young, folded system bisecting obliquely the country, in a SW— NE direction. When coming into being, the orogenic forces attendant on the folding process had pushed upward the sedimentary rocks of the earlier sea-bottom, and these very forces had also been the primary causes that a part of the rocks underwent metamorphosis. Along the fault lines, also the magmatic appeared on surface. The pétrographie composition and the surface formations of the Range are therefore extremely various. Their materials represent sedimentary limestone and dolomite as well as the locally folded sandstone, argillaceous minerals, eruptive andésite, basalt, riolite, etc. From a malacological point of view, the formation of these rocks had a twofold effect: partly (and directly) by the physical and chemical action of the substrates, partly (and indirectly) by the microclimate governed by the physical structure and the physiognomical conditions. The climate of the Hungarian Central Range is not uniform, though the area is not substantial from a geographical standpoint. Differences in the microclimate are even greater than those of the macroclimate. To expound them would, however, go beyond the scope of this paner. The climate of the Range can be subdivided into three characteristical climatic areas. The firts is characterized by an always sufficient precipitationjand humidity content, and a relatively balanced temperature. Such places are to be met with mainly in the Mts. Sátoros, Bükk, Mátra, Börzsöny, Pilis, Bakony, and finally in certain sites of the basalt cones north of the Balaton. This climatic area is highly favourable for the mollusks. The northern wing of the Range is obviously richer in such places. The second climatic area makes up the preponderant portion of the entire Range. The main features are sufficient precipitation and humidity (except for the summer), and a slightly less balanced distribution of temperature. The third climatic area is characterized by the frequency of sites exposed to hot and strong insolation, the considerable fluctuation in temperature, and the rather insufficient amount of precipitation. Such places are rather few in the Hungarian Central Range. Next in line after the conditions of substrate and climate is the respective constitution of the vegetation. Its significance is manifest in the life of the mollusks. There are scarcely any species in places sustaining but a scanty vegetation : on barren cliffs and in sandy deserts. Aside of the physiological importance of the microclimate niches and aerial humidity, vegetation is indipensable as the sustaining factor. The majority of mollusks feed on plants and vegetable detritus. The number of carnivorous species in the Hungarian Central Range is only 4, in contrast with the 148 species shown from the area under consideration. Botanists studying the Central Range had found, when painstakingly mapping its flora, that the northern and southern flanks of the area have different floras and that their dividing line passes through the Mts. Pilis. Geographically, this section belongs already to the southern wing, but its climate and vegetation resembles rather those of the Mts. Börzsöny of the northern region. There live 29 Mediterranean plant species in the southern part]of the Central Range, but only 2 of them have advanced into the northern section. Of the Atlantic (western) species, 10
