Odonata - Entomological Society of Latvia - Latvijas Daba

strongly preferred. Additionally, at two localities, C. elata was the leading species in the habitat of
N. speciosa. Apart from other typical components of the sedgling's habitats, e.g. Sphagnum sp.,
Utricularia sp., Menyanthes trifoliata, Comarum palustre, Naumburgia thyrsiflora, Equisetum
limosum (De Marmels, Schiess 1977; Schmidt, Sternberg 1999 etc.), some rather untypical plant
species occur, such as Thelypteris palustris, Typha latifolia and Hydrocharis morsus-ranae.
Anthropogenic, habitats play a rather marginal role in the habitat spectrum of N. speciosa in
Latvia. These localities may have long-term significance for N. speciosa as bogs occupy large areas
and probably always included a mosaic of habitats, from active peaty post-excavation places to
active raised bogs. It means that in such peat bogs, suitable habitats for N. speciosa can be
established during the succession proccesses.
Current data shows that large populations are rare, but small populations are the most
frequent. This situation is typical for all the Baltic States (Bernard and Wildermuth 2005).
Aeshna subarctica. A subarctica is a Holarctic species. However, the main species' European
range is around the Baltic Sea (Dijkstra 2006; Skvortsov 2010). Current distribution pattern probably
results in part from the diverse intensity of odonatological studies in various regions. An analysis of
a potential basis for such a pattern has not revealed a clear cause as the known distribution of
A. subarctica does not correlate with the delineation of Latvia into physiographic regions (sensu
Ramans, Zelčs 1995) or geobotanical regions (sensu Kabucis 1995). However, the richness and
abundance of raised bogs, thus potential habitats of the species, undoubtedly result in greater
numbers and concentration of its localities. This general correlation is especially recognizable from
the example of western Latvia, occupied by a large raised bog district which is a part of a great
mires chain extending through several countries. Some correlation between the distribution of
A. subarctica and climatic regionalisation (sensu Kalniņa 1995) has also been recognisable as the
majority of known localities (90 %) are situated in two climatic regions (Figure 19). These climatic
regions are characterized by a higher humidity (hydrothermal coefficient 1.6–2.4) and a more
continental climate in comparison with other two climatic regions (Kalniņa 1995).
In comparing the habitats inhabited by A. subarctica in Latvia and other Europe, some
differences were found. Some authors write that species inhabited active raised bogs with pools
with immerged (floating) Sphagnum (Dijkstra 2006), others mentioned that species was found in
post excavation peaty pools (Scholl 2001). In Latvia A. subarctica has been found in raised bogs
with water pools and lakes, as well as in lakes with fens and poor fens, but not found in any of the
surveyed post-excavation peat pools. If compare the water courses where larvaes was found or egg
laying observed, it seems that these water courses are larger than 25 m 2 . This concurrent with
observations in Czech Republic, were the species are occurring in small (ca. 50 m 2 ) peat pools and
large (ca. 1000 m 2 ) peat lakes, but most abundant in pools with surface ca. 300 m 2 (Holuša 2000).
However in Germany egg laying and exuviae’s was observed in small pits made by red deer Cervus
elaphus and wild boar Sus scrofa (Bönsel 1999).
The species composition of vegetation at Latvian localities is frequently relative poor.
Floating Sphagnum cuspidatum is the most frequent and the most abundant representative of the
mosses preferred for egg laying by A. subarctica. Other Sphagnum species as Sph. Magellanicum
and Sph. rubellum, though generally slightly rarer and less abundant, is also selected for egg laying
by the subarctic hawker. Apart from other typical components of the subarctic hawker’s habitats
(for emergence), e.g. Eriophorum sp., Rhynchospora alba, Scheuchzeria palustris, Andromeda
polifolia, some rather untypical plant species occur, such as Carex limosa, and C. lasiocarpa.
Although Holuša (2000) mentioned, that egg laying (and found exuviae) in Carex paupercule zone
were observed.
Although A. subarctica is not found in anthropogenic habitats, e.g. post-excavation peaty
pools, suitable microhabitats were found in several surveyed places. It means that in such peat bogs
suitable habitats for A. subarctica can be established during the succession process.
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