Odonata - Entomological Society of Latvia - Latvijas Daba

decrease with the increase of those of Anax parthenope? Will the population of Leucorrhinia dubia
decrease with the warming of the climate?
Changes of species distribution The largest part (78 %) of the Latvian dragonflies belongs
to the Palearctic or West Palearctic type of current distribution. This is due to the fact that mainly
species with very vast or vast areas of distribution in the Europe part of Eurasia are represented in
Latvian fauna. Four species (Pyrrhosoma nymphula, Aeshna cyanea, Brachytron pratense,
Cordulegaster boltonii) are distributed mainly in Europe with some localities also in the northern
part of Africa and the western part of Asia (Dijkstra 2006). Nevertheless, the distribution areas of
these species are quite vast. Mediterranean – Afrotropic species Anax ephippiger may be observed
in Latvia due to the summer invasions of the species in the whole Europe (von Rintelen 1997; Ott
2001), therefore this species may be considered only a guest species. Sympetrum fonscolombii is
generally related to northern and central part of Africa region, south-western part of Asia and
Mediterranean region. In northern regions the species can be found irregularly and rarely, but in the
years of invasion it can be quite common (Dijkstra 2006).
Data on dragonflies are available from whole territory of Latvia both in historical (1778-
1990) and current (1991-2010) periods (Figure 3). This scope and dividing line are based mainly on
several obstacles, associated with fact that in 1990 Latvia withdrew from USSR. These (political)
changes generated consecutive changes in science (availability of information, publications,
contacts with western scientists etc.), in agriculture (less chemicals, in the first years – development
of small farms), in forestry (more and more active forestry) and social process (project activity,
greater mobility of scientists) (CSP 2011). The same division is used in dragonfly Atlas of Poland
(Bernard et al. 2009).
Although the historical period is the longest, in this period the data were obtained about a
smaller territory (13 % of all squares of Latvia) than in the current period (23 % of all squares of
Latvia). Nevertheless, the survey of Latvia has not been homogenous neither in the historical, nor
the current period. The vicinity of Rīga and Sigulda has been surveyed more accurately, which is
related to the places of work and residence of dragonfly researchers both in the historical and the
current periods. Thoroughly surveyed are also some of the specially protected nature territories
(Gauja National Park, Protected Landscape Area ‘Ziemeļgauja’, Teiči Nature Reserve etc.). The
eastern part of Latvia and individual territories in Kurzeme and Zemgale have been only partially
surveyed, which is due to the greater distances from the places of work and residence of dragonfly
researchers, research centres and difficulties to reach these territories during the historical period.
The number of identified species in one square is mainly related to the type of research
activities. The largest number of species is identified in specially protected nature areas or in places,
where the research was carried out longer, for example, the Engure lake, Gauja National Park
(Спурис 1951; Inberga-Petrovska 2003; Kalniņš 2006; Kalniņš et al. 2007), in places where some
projects or researches were carried out (Kalniņš 2002b; Mathes, Mathes 1997; ES LIFE... 2007) or
near the places of work or residence of dragonfly researchers (Figure 17). The quantity and the
quality of the observations were affected also by other aspects related to dragonfly research. Some
species, for example, Calopteryx genus dragonflies are easier to observe and identify and they are
often photographed. At the same time, other species are more difficult to observe, for example,
Epitheca bimaculata (only imagines!!), or they are easily confused with other similar species
(Coenagrion lunulatum). Some species are registered more often, as their flight period is longer and
lasts several months in the summer. At the same time, the imago activity period for Coenagrion
armatum is in spring, when dragonfly observations are not as intensive. Thus, when comparing the
distribution of species with different imago activity periods, a faulty conclusion about the
distribution of species may arise. Simultaneously, it must be taken into account that different
habitats are not research to equal degree, for example, raised bog habitats were researched very
little in the historical period. Perhaps, this is the reason why almost all Aeshna subarctica localities
have been identified in the current period, as the surveying of bogs has become more intensive.
Also the methods of dragonfly inventory affect the results. Since 2005, when the author started to
collect Anisoptera exuviae, the number of Epitheca bimaculata localities has grown considerably.
Another aspect is that the survey of squares has been carried out to various degrees (from 1-2
observations of the species to several surveys throughout the season for several years). These and
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