ISSN 10623590, Biology Bulletin, 2013, Vol. 40, No. 2, pp. 217–220. © Pleiades Publishing, Inc., 2013. Original Russian Text © S.V. Bugmyrin, L.E. Nazarova, L.A. Bespyatova, E.P. Ieshko, 2013, published in Izvestiya Akademii Nauk, Seriya Biologicheskaya, 2013, No. 2, pp. 240–244.
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Concerning the Problem of the Northern Limit of Ixodes persulcatus (Acari: Ixodidae) Distribution in Karelia S. V. Bugmyrina, L. E. Nazarovab, L. A. Bespyatovaa, and E. P. Ieshkoa a
Institute of Biology of the Karelian Research Centre of the Russian Academy of Sciences, ul. Pushkinskaya 11, Petrozavodsk, 185910 Russia b Institute of Northern Water Problems of the Karelian Research Centre of the Russian Academy of Sciences, Aleksander Nevsky pr. 50, Petrozavodsk, 185030 Russia email:
[email protected] Received October 12, 2011
Abstract—The influence of changes in climate conditions on the abundance and formation of the northern limit of Ixodes persulcatus distribution in Karelia has been studied. It has been demonstrated that the territory in which the heat provision is sufficient for the development of ixodid ticks significantly increased during 2000–2007. Thus, it favored an increase in the abundance and enhanced distribution of I. persulcatus. DOI: 10.1134/S1062359013020039
The ixodid tick Ixodid persulcatus Schulze, 1930 is widespread and common in Karelia. It is the main vec tor of tickborne encephalitis and Lyme disease. Ear lier research works have demonstrated that the north ern limit of the range of I. persulcatus in Karelia goes along the conditional line connecting Gimoly, Padany, Masel’gskaya, and Danilovo (Kheisin, 1950; Lutta et al., 1959; Korenberg, 1985). Recent studies have shown that not only has the abundance of ixodid ticks living in the region increased significantly, as com pared to the data obtained in 1970–1980 (Bespyatova et al., 2006), but there were also new findings of the taiga tick outside its traditional range (Jaaskelainen et al., 2006; 2011; Bugmyrin et al., 2011). One of the limiting factors that determines the dis tribution of ixodid ticks in the north is temperature. The minimum heat provision of the ground needed for the development of I. persulcatus is the accumulated temperatures equal to 1400–1500°C. In European Russia, the northern limit of the taiga tick’s range coincides with the isoline of the accumulated temper atures equal to 1400°C during the period with a stable daily mean temperature of more than 10°C. The accu mulated temperatures during the period with a stable daily mean temperature of 5°C should be not lower than 1600°C (Korenberg, 1985). The global trends in climate dynamics can be an important factor deter mining changes in the range of I. persulcatus within the northern periphery. The aim of this study was to estimate the influence of changes in th eregion’s climate on the abundance and distribution of I. persulcatus in Karelia.
MATERIALS AND METHODS The meteorological analysis was based on the series of the daily mean air temperatures obtained from 28 meteorological stations (MSs) of Karelia during the years 1951–2000. The accumulated daily mean tem peratures above 5 and 10°C during 2000–2007 were calculated using the data on 9 MSs of the Northwest ern Territorial Administration for Hydrometeorology and Environmental Monitoring, which are located in the central and northern regions of Karelia. The accu mulated temperatures were calculated for the periods lasting from the stable transition of the daily mean temperatures through the corresponding limits in spring and autumn for each period under study. Then, the average accumulated temperatures above 5 and 10°C for 2000–2007 were calculated. The obtained results were compared to the data in the Atlas of KarASSR (1989) and the Climate of the USSR: A Handbook (1965). The material on the distribution and abundance of ixodid ticks was obtained as a result of route expedi tions, which were organized in central Karelia in June 2008 and 2010, in the area between 63°15′ and 63°42′ N (see figure). Adult ticks were collected by flagging (0.7 × 1.1 m) according to the conventional procedure and further recalculation of the relative abundance in number of ticks per flagkilometer (flagkm). In all, 28.8 flagkm were performed and 114 ticks were col lected. The living ticks were identified using a binocu lar microscope (×16) and according to the method ological recommendations suggested by Fillipova (1977). To estimate the abundance of the larval I. persulca tus, the ticks were collected from small mammals. The mammals were caught with Gero snap and live traps
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1
2 3
Wh
4
ite Se
5
a
1400°C 1600°C
1400°C
Petrozavodsk
0
50
100 km
Schematic map of the research site. 1 is sites where small mammals were caught; 2 is the area of route investigation of ixodid ticks in 2008 and 2010; 3 is the northern limit of the ixodid tick range in Karelia, based on the data from 1950; 4 is isotherms (The Atlas of KarASSR, 1989); 5 is the isotherm calculated based on the data from 2000–2007.
arranged in two areas (figure). In the first area, a total of 750 trapdays (td) were examined, 11 specimens of Myodes glareolus were trapped June 17–20, 2008. In
the second area, 200 td were examined, 11 spm. of M. glareolus were trapped June 17–19, 2010. The lar vae and nymphs were fixed in 70% ethanol. In order to BIOLOGY BULLETIN
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CONCERNING THE PROBLEM OF THE NORTHERN LIMIT
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Abundance of Ixodes persulcatus in the research polygon Examined, Collected ticks, Number of ticks per flagkm ind. flagkm
Mean number of ticks per flagkm
Site of collection
Coordinates, N
I
southward of 63°17′
5.4
75
13.9
6/6
13.5 ± 5.3
II
63°17′–63°27′
8.3
18
2.2
4/11
1.3 ± 0.8
III
northward of 63°27′
15.1
21
1.4
1/14
0.9 ± 0.8
N/Ntotal*
Note: * N is the number of routes on which ticks were found, Ntotal is the general number of investigated routes.
further identify the tick species, temporary prepara tions were made using the ForaBerlese liquid. The ticks were identified according to the methodological recommendations suggested by Filippova (1977). The infection rate among small mammals was estimated according to prevalence (the percentage of infected hosts) and the abundance index (mean abundance of ticks per host). RESULTS AND DISCUSSION Based on the geographical characteristics, the area of investigation was divided into three research poly gons (table). In the first (southern) polygon, the abun dance of ticks made up 13.9 specimens per flagkm. All the routes were examined from south of the settle ment of Padany near the village of Pogost (63°16⬘ N, 33°23⬘ E). The earlier (Kheisin, 1950) northernmost findings of I. persulcatus in Karelia were registered here. At the same time, there are data on an extremely low rate of infestation by ixodid ticks detached from cattle (0.05%, average abundance of the I. persulcatus females equals 0.05); no information about flagging is provided. We detected I. persulcatus along all the routes. Moreover, the abundance of ticks reached up to 30 individuals per flagkm in some sites. In the second polygon, the abundance of ticks was 2.2 specimens per flagkm (table). The ixodid ticks were found on 4 of 11 routes. The highest abundance (8.7 ind per flagkm) was observed in the village of Yukkoguba (63°24′ N, 33°5′ E). Two larvae and two nymphs of I. persulcatus were collected from 11 speci mens of the bank vole, which were caught in this area (63°23′ N, 33°22′ E). The prevalence and the abun dance made up 18 and 0.18, accordingly. In the northern polygon (northward of 63°27′ N), the abundance of ticks was 1.4 specimens per flagkm (table). The ixodid ticks were registered on only 1 (the area of Kuznavolok 63°42′ N, 33°05′ E) of 14 routes, their abundance was 8.1 specimens per flagkm. Variations in region’s ground air temperature are indicative of the positive trends in global temperature. On average, the general trend of ground air tempera ture changes in Karelia (based on data from 28 MSs) is 0.2°С over 100 years (1900–2000) and 0.6°С over BIOLOGY BULLETIN
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50 years (1951–2000). In general, the yearly tempera ture of Karelia did not increase monotonically during the 20th century (Nazarova, 2008). The warming of the 1930s was replaced by a fall in temperature in the 1960s–1970s, which was then replaced by an increase in temperature at the end of the 1980s. If we consider monthly changes in the temperature for 1951–2000, the trends are not so clear. The estima tion of the changes in ground temperature allowed concluding that the clearest positive linear trend of the monthly mean temperature was observed in March and varied from 3 to 5°С at different stations. At the same time, according to the Student’s criterion, its significance made up 95% at all the stations. In April, the warming process progresses more slowly than in March. These trends are statistically unimportant, but they were also registered at all the stations. For the years 1951–2000, trends towards warming were observed from January until May. In summer and the major part of autumn, the temperature changes were directed differently and had low absolute values (lower than 1.7°С over 50 years). They are replaced by a fall in temperature by 0.4–1.1°С over almost the whole country. Clear positive trends (increase of air temper ature) within the annual variation are dominant. The dates for which there was a stable transition of temperature through 5 and 10°С towards its further increase and decrease during 2000–2007 were shifted when compared to the longterm average values. The shift made up 6–8 days in spring and 10–12 days in autumn for temperatures above 5°С, as well as 4– 6 days in spring and 10–12 days in autumn for temper atures above 10°С. As a result, the periods with air temperature above the mentioned maximum values lasted 7–13 and 16–20 days longer, accordingly. Together with the general increase in temperature, this process favored the gathering of high accumulated temperatures. From analyzing the obtained and published data (Atlas of KarASSR, 1989), it can be concluded that the area for which the mean daily accumulated tem peratures above 10°С are greater than 1400°С has increased in Karelia, and its limit has shifted north wards (figure). In 2000–2007, the mean daily accu mulated temperatures above 5°С in Karelia were more
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than 1600°С and made up 1750–1800°С even in the northernmost regions of the republic. The obtained data agree with the information about the northward increase of potential and calculated range of the taiga tick based on the climatic parameters (Yasyukevich et al., 2009). The detection of ticks in the northern polygon is the northernmost finding of the adult I. per sulcatus in Karelia at present. In 1958, four larvae of I. persulcatus were found here while observing 268 small mammals (data were obtained from the Archives of the Karelian Research Center, Russian Academy of Sciences, Petrozavodsk). In June 2010, five larvae of the taiga tick were collected from 11 specimens of the bank vole. The prevalence and the abundance rate made up 27 and 0.45, accordingly. Therefore, the abundance of the taiga tick at the northern limit of its range has significantly increased when compared to that during the earlier period. A high abundance was registered to the south of the set tlement of Padany, which is mainly covered by the sec ondary mixed forests serving as a common range of I. persulcatus in Karelia. The area significantly decreases towards the north, the primary taiga forests (spruce and pine) become dominant, and the distribu tion of ticks is mosaic. Conditions favoring the devel opment of I. persulcatus are formed in close proximity to villages or mountain areas. Kuznavolok may be an example of this situation. Here, the secondary mixed forest was formed due to the gradual overgrowth of a small grass meadow (~1 km2). It cannot be excluded that there are some local focuses of ixodid ticks to the north of this point. This can be proved by findings from the eastern part of Finland (Burmygin et al., 2011). Nevertheless, additional route investigations are needed for further clarification of the northern limit of the taiga tick distribution. At present, there is suffi cient evidence to consider that this species is wide spread in territories outside its common range, which is, in turn, proved by the recent findings of I. persulca tus in Northern Europe (Jaakelainen et al., 2011). ACKNOWLEDGMENTS We are grateful to the scientists of the Karelian Research Center, Russian Academy of Sciences, for their help during the analysis of archival materials, and to S.A. Korosov and E.S. Akhmedzhanov for partici pating in the field investigation. This work is supported by the Federal Target Program: Scientific and Academic Personnel of Innovative Russia, 2009–2013 (no. 02.512.11.2171, no. P1299).
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