Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 90. (Budapest 1998)

Medzihradszky, Zs. ; Bajzáth, J.: The occurrence of arctic-alpine Betula species in the Hungarian Pleistocene

ches there are two dwarf species: Betula nana and Betula humilis. Another interesting birch tree is Betula pubescens ssp. tortuosa which differs significantly from the other ones such as Betula pendula and Betula pubescens. Not only the nutlets of Betula were found but other macroremains of these species - twigs, leaves, buds, bud scales and fruit scales - are also parts of the fossil assemblage. The dwarf birches and Betula pubescens ssp. tortuosa is reported from Hungary for the first time. Here we provide a detailed description of these birch species. Betula nana LlNNAEUS, 1753 (Figs 1-4) Description. Leaves (Fig. 1). Very characteristic, deeply and regularly toothed leaves of rounded shape and small size (0.5-0.8 mm). The venation of the leaves is typical for the genus. The terminal veins in the middle part of the leaves are curled. Fruit scales (Fig 3). The fruit scales are deeply lobed, small, 1.9-2.0 mm 2-2.1 mm in size. The angles between the three lobes are narrow and U-shaped. The middle narrow lobe is the same size or a little longer than the other two. The width of the lobes is nearly the same. Nutlets (Fig. 4). The rounded small nutlets are 1.25-1.6 mm 0.8-1.5 mm in size. The broadest part of the nutlets is almost of the middle section. The narrow wing around the body of nutlets is 0.15-0.3 mm in size. Discussion. Three almost whole leaves, four fruit scales and 15 whole nutlets were found in the fossil assemblage. Several leaf fragments and nutlets of cf. Betula nana and numerous buds and budscales were also recovered. The determination of Betula nana from the bud scales is uncertain. The measurements of the budscales (lxl mm) and their triangular outline resemble those of Betula nana. The other macrofossils unambiguously proved to be remains of Betula nana. These are the first macrofossil data of Betula nana from the Hungarian Pleistocene. An earlier determination of wood remains of Betula nana was uncertain and it lacked a radiocarbon age (ZÓLYOMI 1953). This dwarf birch is a typical species of the glacial stages throughout Europe (LANG 1994). It occurred abundantly in the Weichsel-pleniglacials and Late-glacial. Betula nana belonged to the so-called "Z)ry<xy-flora" of that time, characterizing the glacial tundra or steppe-tundra vegetation in Europe. Here it also occurred as a characteristic member of "Dryas-flora". The southern limit of the range of Betula nana in Europe reached the Alps during the Late-glacial similarly to its present distribution (LANG 1994). Nowadays Betula nana is an arctic-subarctic-alpine element living in terrestrial habitats (mountain birch zone and forest-tundra) and in oligotrophic mires (bogs, moors) as well. In the northern Fennoscandia Betula nana lives either in terrestrial habitats or in mires showing the different ecotypes of this species. Besides the continuous arctic-subarctic-alpine distribution area of Betula nana in northern Europe, there are some other disjunct localities in Central and Western European mountains. There are only two localities in the Eastern Carpathian Mountains where Betula nana is a glacial relic species occurring only in oligotrophic bogs or moors. The main plant association where Betula nana belongs to today is characterized by Sphagnion magellanici. It is possible that of