What does influence large hoverfly activity more? - Individual host plant traits or actual weather conditions?

Janovský, Z. (1), Pavlíková, A. (2), Říhová, D. (3), Mikát, M. (3), Vosolsobě, S. (4), Ponert, J. H. (4,5)

1) Dept. of Botany, Faculty of Science, Charles University in Prague
2) Dept. of Zoology, Faculty of Science, University of South Bohemia, České Budějovice
3) Dept. of Zoology, Faculty of Science, Charles University in Prague
4) Dept. of Experimental Plant Biology, Fac. of Sci., Charles University in Prague
5) Prague Botanical Garden

The pollination activity of hoverflies within a meadow depends in general on two factors (i) actual weather conditions and (ii) floral traits of plants they visit. We investigated the interplay between these two groups of factors in areas of our study sites with mono-dominant flowering stands of Succisa pratensis. We observed activity of our focal hoverfly species (Eristalis tenax, E. interruptus and Helophilus trivittatus with minor proportion of H. pendulus) on different individuals of S. pratensis. Besides floral traits we also recorded mean solar radiation and wind speed for the 10-minute observation blocks. We conducted our research in three successive years on two sites.

The results suggest that E. tenax and E. interruptus had very similar preferences with respect to weather factors and floral traits. Both of them were influenced in their occurrence approximately three times as much by floral traits than by actual weather. This discrimination among the plant individuals was sharper in the time of peak hoverfly activity. On the other hand, Helophilus spp. discriminated plants worse, while the amount of variation by actual weather conditions remained approximately the same as in the preceding species.

We hypothesize, that this might be the result of the overall preferences of the studied hoverfly species, since E. tenax and E. interruptus tended to concentrate on Succisa pratensis, whereas Helophilus spp. preferred other plant species. It seems therefore likely that hoverflies discriminate better among their preferred host plants than the others.

Presentováno na 6. symposiu o pestřenkách konaném v Glasgow ve dnech 5.-7.8. 2011.

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