il ' ii - Northern Research Station - USDA Forest Service

THE ZOOGEOGRAPHIC SIGNIFICANCE OF EUROPEAN AND ASIAN
-GALL MIDGE FAUNAS (DIPTERA: CECIDOMYIIDAE)
Marcela Skuhravfi_,VacIavSkuhravy2 A
Czech Zoological Society, CZ-128 00 Praha 2, Vinicna 7, Czech Republic
2 Institute. of Entomology, Czech Academy of Sciences, CZ-370 05 Ceske Budejovice, Branisovsk/L 31, Czech Republic
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Abstract.--Between 1955 and 1997 we carried out extensive studies of gall midge at
1,600 localities in Europe and in 17 localities in Asia (Siberia). Occurrence data collected
by earlier authors are summarized and compared with our data. Our analyses
, show that the gall midge species composition in Europe is strongly influenced by
geographical and altitudinal position, climatic factors, vegetation type and human
activities. Analysis of our collected data make it possible to produce zoogeographic
distribution maps for gall midge species, to recognize long-term changes in population
dynamics and to determine which species should be considered
nature conservation.
threatened with regard to
INTRODUCTION summarization of all data gathered by earlier authors but
also which we enriched by results of our own investiga-
In zoogeographical studies of gall midges, it is essential tions (table 1). The gall midge fauna of each territory
to gather extensive data on the horizontal and vertical was evaluated from two points of view: geographic and
occurrence of each species throughout a larger study zoological. Geographic data present two features of
area. The more data are collected, the more reliable and gallwasp distributions" (a) Spatial distribution is
meaningful the conclusions that can be drawn. It is represented by the gall midge species found at individual
possible to begin in smaller areas but it is necessary to localities within a larger region. (b) Vertical occurrence
extend such investigations gradually to larger and larger is shown by the average numbers of gall midge species
areas. We have therefore broadened our investigations which occur in the rising altitudinal zones. When
from a starting point in 1955 in the former Czechoslova- possible, past and present distributions are compared to
kia to include other countries in Europe and Asia. The examine long-term changes in population dynamics.
"following approaches are very important in addressing
zoogeographical questions: We used the same collecting method at each sample
.- location. We walked slowly through various biotopes in
1. Summary of scattered gall midge occurrence data each location for between one and several hours,
gathered by earlier authors in various parts of searching and collecting all galls on plants, or plants
Europe in the past. inhabited by mites, aphids or other insects, or rusts, in
21 Obtaining new data on the present occurrence of which larvae of gall midges may develop. All findingsl
' gall midges species inthe same regions, were recorded, including notes about the local abundance
' 3. Extension of investigations to little-explored of species. Each locality was investigated only once b_
" areas, this method.
MATERIALS AND METHODS In 1955, at the beginning of our studies we developed a
strategy for systematic investigations of the gall midge
We use the term fauna to indicate the sum of all gall fauna of the Czech Republic. Localities in which we
midgesspecies recorded from a particular area, country intended to collect galls were identified throughout the
or period. Other authors have described the same country using the map with Ehrendorfer's network, as far
concept Using terms including species richness, species as possible with one locality per 11 x 12 km area
•diversity and faunal composition. We generated lists of (described in detail in Skuhrav_i 1994). We used the
' gallmidge species forming partial faunas of several same grid-based method in Slovakia (Skuhrav_i 1991) but
European countries in which we included not only the this systematic approach could not be applied to the
whole of Europe due to time constraints.
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