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TERBORGH et al. l 990) found that the number of species remained unchanged ordecreased in the edge, regardiesS of edge type. In another large Study, Lovejoy et al. l 986) also mund that the number of hird species declined in the edge of an AmaZonian rain forest, as a consequence of high levets of habitat specificity. The similarity and consistency of these resulis os fragmentation and edge effecis suggest remarkably different responses of temperate and tropical forest bird communities to forest edges Fig. l).
THREE ALTERNATIVE EXPLANATIONS FORTHE DIFFERENT EFFECI S OF EDGES ON BIRDSIN TROPICAL VERSUS TEMPERATE FORESTS
For the sake of simplicity, and because of the avallability of data. I analysed historical and bird distributionat data Dom the South-American tropicat the AmaZon basin), and the European temperate Zones. It is possi hie to include other regions, such as the Afrotropical or North-American temperate Zones, but theremight be difficulties. e. g. i) the lack of quantitati ve data Dom other tropical rain forest edges: or ii) the different biogeographic siluation of the European and the North American continenis, due to the position os mountain barriers UDVARDY
Below. Ι Suggest three alternative hypotheses for the explanation os different edge effecis. The firsi and second hypotheses consider Space and time, respectively, the third e valvates human impacis. These hypothesis are not exclusive. the described processes can interact. HoweVer, my aim was to ciearly ShOwthe possibie mechanisms, thus I emphasi sed the differences between the processes rather than the similarities and interactions. Hypothesis l: Different geomorPholon in Eurme and Amazonia The different geomorphology of Europe and Amagonia has resulted in different patchiness of vegetation on a continental scale. The area of the AmaZon
While the former is only one drain age area, the lalter consists of many ri Ver bastias, hi gli motintains, hilis, plains and lakes, and is hordered by a rugged Seas hore for thou sancis of kilometres, resulting in many very different Vegetation types. That is, on a continental scale Europe is natural ly more patchy than Ama-Zonia. The difference belween the scale of patchines s in the two Zones is apparentis we consider the drainage areas: AmaZonia is one large basin, whereas in Europe the has ins are sinalter by nearly an order of magnitude Table 2). Even thesum of the largest drain age areas in Europe is tess than that of the Amagon basin.
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Table 2. The area of Ammonia and the three largest European drainage basilas. and Europe sin km )Locali ty
during the glaciationS mari in Euro ebrom a historical potiat of vlew, plant communities during the glaciations must be viewed as impermanent in Europe. Changes have Occurred continuous ly even on a fine time scale sca. l000 years) ROY et til. l 996). Similar changes may have occurred at different times in different paris of Europe. Or the changes may have differed belween geographicat areas HUNTLEY l 988). During the last glaciation sabout 20 000 to l8 000 yr BP), there were nine very different vegetation types in Europe. including arctic tundi a. boreal Vegetation, Open wOOdland s. and semideseris FRENZEL et al. l 992). Furthermore, vegetation Zones have Varied considerably over the last ca. l0 000 years. There was a periodicat expansion os non-forested hi omes during the glaciations and extension of foresis during the interglaciations VARGA l99 ). Therefore, the predom in ance of edge bird species may be an adaptation to the discontinuousty wooded habitat that was extensive in the non-glacialed paris of Europe HUNTLEY l 988), and to the continuous lychanging patiern of Vegetation COVer. The history of tropical rain foresis during the glaciations was different. Conventionat wisdom suggesis se. g. UDVARDY l 983), that there were no majorchanges in the vegetation the changes in the climate were moderate, and the temperature in tropical lowland s remat ned hi gli during the glacials . These areas were relative ly stabie in a paleoniological sense HAFFER l98 l). Howe ver there is controversy abolit how much disturbance there was. The recent view is that Ama-Zonia was not as stabie as previ ously belleved WEBB l 995). For example STUTE et al. l 995) showed that the temperature in lowland Bragit was 5.4'Ccooler during the last glaciat than toclay. CAMPBELL sl 99 l) argued that there was even a large lake in the Amagoni an basin during the late Pleistocene. Nevertheless. ''C variation in Amaronian solis suggesis that the reti eat os foresis might occur Only on a locat scale and not on regional ones MARTIN ELLI etat. l 996. butsee DESIARDINS et al. l 996). Besides the large Scale proceSSes, there were
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changes on a finer scale as wello the rivers undulated acros f the lanciscape, lensecondary foresis in vast meanderS. and carved primary forests. The changingvegetation patierns may explain the high species diversi ty of tropical foresis onthe basis os fragmentation due to climatic changes when the AmaZoni an forestswere reduced to severat forest is laiads), and the creation os refugia HENGEVELDl 990. UDVARDY l 983). Both bird and plant data seem to confirm this idea PRANCE l98 l. l 996). However, a very recent research on pollen records indicate that glaciat age forests were comparabie to modern forests COLINUAUX et
The recent view that AmaZoni an vegetation was not stabie during glaciations seems to be in contradiction with this hypothesis. However, historical data of the glaciations suggest that, although the tropical lowland rain forest habitatswere not as stabie as heli eved. the variation os habitais and the scale of changesare different stom those in the temperate Zone. For ex ample, the totai area of the supposed refuges in tropicat Sotith America Fig. 9. 9 in PRANCE l98 l) is almost in the fige of ali os Europe, so they should he viewed as permanent on the spatiat scale on whicli Europe must he viewed as impermanent. Indeed, the response of Vegetation in the Southern Hemisphere to glaciations has been substantialty different frona that in the Northeria Hemisphere MARKGRAF et aL l 995). The relative stabili ty of tropical rain forests on a 'European' scale might have allowed the adaptation of hird species to continuous forest habitais and the spectation offorest interior species. Humid forests are ornithologicalty fairly homogeneotis onlocat and regional scales OLROG l 969). Hypothesis 3 Human habitat alternatis et wGS more ProrioiariCed in Eurme thian in Amazonia The human impact on the biosphere has a long history. For example, HONGet til. sl 994) showed that lead pollution occurred on a hemispheric scale as earlyas 2 00 years ago by Greek and Roman civili sations. Other human disturbances during the Quaternary greatly diminished and fragmented European forests whereas in North America temperate forests were far more extensive and continuotis MONKONNEN t 994). Obvious ly. the tropical forest of Sohith Americas hould be viewed as even more extensive and continuotis than North Americansoresis, hecati se of the s horter history of human disturbance. Thus, Europe al- ready had an artificiat ly fragmen ted forest land scape severat millennia ago, but in AmaZonia there was no Such strong disturbance HANNAH et ah l 995). Human populations were establis hed in the lalter area ca. l0 000 years ago sBUSH 9 CO
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EDGE EFFECT IN TROPICAL VERSUS TEMPERATE BIRD COMMUNITIES
Temperate Zone bird communities are adapted to an impermanent habitat. with relative ly smali patch si Ze son a continental scale), whereas tropical ones ure adapted to a more stabie habitat, where there are large patches. Theres ore, Species that tolerate edge habitats are more abundant in temperate Zone bird communities than in the tropical communities, where the relative number of species adapted tointerior habitat s is much higher. This may be one factor that accounts for thehigh tropical diversi ty because interior communities are more dissimilar than edge communities sHARRIS & SILVA-LOPEZ l 992).) In a recent review TURNER l 996) argued that fragment edges may be inhospitable not only to birds but tot he majori ty of forest specieS. I argue that the different communi ty structu res of tropical and temperate forests may be explained by the above three hypotheses. The three processes spatiat variabili ty. temporal changes and human disturba iaces) together created relative ly more edges in Europe than in Amagonia during the last severat thou sand years. This led in turn to hirci communities adapted to fragmen ted habitat s. containing more edges than tropical forests. The different history of the two Zones during the Pleistoce ne resulted in disse ferent hird communities. Besides the different ratio of edge and interior hird Species. the number and composition of guilds also differs. Tropical communities harbour many frugi Vores, usu atly large-bodi ed species, whereas in the temperate communities insectivores compri se the large majori ty of bird species TER BORCHl 985). Large frugivores are e specialty sensitive to tropical forest fragmentation
A future research task is to follow the effecis of tropical deforestation and habitat fragmentation in the Amagon SKOLE L TUCKER l 993). including de-tailed analysis of edge effecis in different successional phases of the rain fore sis. It is clear that more samples frona the litige tropical rain forests will he required totest these three hypotheses and to determine their relative importance.
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EDGE EFFECT IN TROPICAL VERSUS TEMPERATE BIRD COMMUNITIES
11 458 63. SKOLE, D. 9 TUCKER, C. l 993) Tropical deforestation and habitat fragmentation in the AmaZon satellite data hom l 9 8 to l988. Science 260 l 905-l9l0.
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THREE NEW GENERA OF LAUXANI IDAE DIPTER A) FROM PAPUA NEW GUINEA
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were used but actualty the se three new genera are peculiar en Ough to he charac teri Zed eas ity. In vlew of the richness of the New Guine an lauxani id fauna, this paper cannot be more than only a minor contribution to their beller knowledge.
In the descriptions we follow SHEWELI 's l98 P) termino logy. All the type- specimens of the new species below are deposited in the Diptera Collection. De part ment of Zoology. Hungarian Natural History Museum. Budapest sHNHM) orin the Australi an Nationat In seci Collection. Calaberra ANIC).LAUXANI IN AE
Etymology. This new genus is named after Dr S. P. KlM Canberra) for his great achi eve-ments in studies of the Australi an Laux antidae.