DISTRIBUTION IRREGULARITY OF IMAGO IXODES PERSULCATUS IN WEST SAYAN MOUNTAIN FORESTS

About author:

R.L. Naumov, Martsinovsky Institute of Medical Parasitology and Tropical Medicine. M. Pirogovskaya, 20, 119830 Moscow, Russia

Acknowledgments:

Автор благодарит всех многочисленных участников работ Саянской экспедиции ИМПиТМ, начальником которой он был с 1967г.

Annotation:

Distribution irregularity of imago Ixodes persulcatus in West Sayan mountain forests was estimated as dispersion coefficient K=c2 /x, where о — standard deviation, x — mean amount of ticks (per sample).

Results of 341 standard censuses of ticks per certain distance of flagging were used for the analysis. Total length of the distances was 384.05 km. Sample dimension was taken 25 m. Data of 104 censuses more than 2 km each were analysed separately. Total length of these censuses was 248.1 km. Sample dimensions were 25, 50 and 100 m (25, 25x2 and 25x4 m). Every census was conducted within a single altitudinalzonal complex. The vegetation of a complex was relatively homogeneous as far as it is possible in the mountains.

Besides, a 5-day special collection of ticks in a 500 m portion of a ruined road was conducted. Sample dimension was 2.5 m. For the analysis, samples were aggregated into groups of 5.0, 12.5 and 25 m of flagging. In a 500 m distance of another road the ticks were calculated once, using 1 m samples. For the analysis the distances were aggregated into pools of 2, 5, 10 and 25 m.

The analysis of the material has shown that imago Ixodes persulcatus distribution is aggregated, with high diversification of natural conditions in low and middle mountains of West Sayan. Aggregation degree increases with growing vegetation diversification and ticks prevalence.

The diameter of one aggregation area fluctuates from several to 100 m and probably more, according to natural conditions. In some cases two-step hierarchy of aggregations was observed; this is observed more often when tick prevalence is high. In many cases one can predict the presence and the size of aggregation, judging by the most clear character, i.e. vegetation charac-teristics. But sometimes it is impossible to judge upon the presence of aggregations from the external signs.

Different altitudinal-zonal complexes, both within one altitudinal zone and in different zones, show the same peculiarities of ticks distribution. The type of tick distribution is not a population characteristic but fully depends on the distribution of environmental conditions.

In the more homogeneous forests of plains, tick distribution seems to be less aggregated and aggregation area can be much larger.

 

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