Odonata - Entomological Society of Latvia - Latvijas Daba

less than 100 observations and only 8 have less than 10 observations. This means that, at least
partially, the obtained information is a precise and correct representation of the distribution of most
species in Latvia.
4.2. THE SPATIAL DISTRIBUTION OF DRAGONFLY IMAGINES IN MICROHABITATS OF RAISED BOGS
Population research During the research 14 dragonfly species were found and three of them
were singled out as dominating species – Enallagma cyathigerum, Lestes sponsa and Leucorrhinia
albifrons. The greatest diversity of species and the greatest number of individuals was found in
habitats with open water bodies. As many tyrphophilic (or: typical for mires) species need open
water areas (van Duinen et al. 2003; Mazerolle et al. 2005), tree vegetation negatively affects
dragonfly species richness (Corbet 2004). This explains the fact that the highest number of
dragonfly species was observed in bog pools in open areas. However, the number of dragonfly
species was also higher in pools in pine stands. Here an important role is played by the density of
trees and the shading it creates. If the tree vegetation is sparse and does not produce much shading,
then the presence of trees is not the main negative aspect for any of the species. For example,
Leucorrhinia dubia is sometimes observed flying in forests (Pajunen 1962). The lowest diversity of
dragonfly species was recorded in an open bog area of vegetation without open water areas and an
insignificant presence of trees. These areas are characterized by a complex of hummocks and
depressions, where there was not a large variety of dragonfly species (Suh, Samways 2005). On the
other hand, these are suitable habitats for specialist species (species with a very narrow ecological
range, the existence of which requires very specific conditions) like Somatochlora arctica (Dijkstra
2006).
Dragonfly communities are associated with vegetation forms in raised bogs. Lestes sponsa
occurs in the bogs where vegetation has medium height and is highly layered to provide protection,
for example a cover of Calluna vulgaris (Hammond 1983; Sternberg, Buchwald 1999). However,
Corbet (2004) observed that the occurrence of Lestes sponsa is closely connected to the presence of
thick and high vegetation at shores. The Calluna vulgaris with Andromeda polifolia vegetation type
had the greatest percent cover (24.8%) within transects of sampling plots. DCA analysis showed
that Leucorrhinia dubia and Libellula quadrimaculata were associated with this vegetation type.
However, Calluna vulgaris is an important vegetation type also for Leucorrhinia dubia and
Sympetrum danae, as these dragonfly species rest on this plant species (Pajunen 1962; Sternberg &
Buchwald 2000). It is known about Libellula quadrimaculata that it preferably stays in vegetation
of shores (Chwala, Waringer 1996). A significant relationship was found between Enallagma
cyathigerum and Ledum palustre and Vaccinium uliginosum vegetation. However, it is mentioned
in the literature that Enallagma cyathigerum preferably flies above open water and prefers rich
vegetation along shores (Macan 1977). In our study, Ledum palustre-Vaccinium uliginosum
vegetation was mostly found along the shores of bog lakes and likely provides shelter from wind
and hiding places for Enallagma cyathigerum (McPeek 1989; Corbet 2004), or is associated with
breeding behaviour (Van Gossum et al. 2004).
Many dragonfly species hunt, oviposition etc. directly above the surface of open water and
floating vegetation. Egg-laying females and patrolling males also gather in such places (Inberga-
Petrovska 2003; Corbet 2004; Dijkstra 2006). Correlation analysis showed that open water is
important for Enallagma cyathigerum, corresponding with the data of other observers (McPeek
1989; Van Gossum et al. 2004). However, the DCA ordination showed a greater association of
Anax imperator, Aeshna juncea and Aeshna grandis to open water. These species are known to
patrol above the surface of the open water (Sternberg, Buchwald 2000). Correlation analysis and the
DCA ordination showed an association between the surface of the open water and Leucorrhinia
albifrons. Floating water plants are known to be important for Leucorrhinia albifrons (Pajunen
1962).
The species assemblages identified by TWINSPAN were related to specific habitats that
mainly differed in cover of water. Libellula quadrimaculata and Leucorrhinia dubia, which were
indicators of species assemblages, are typical in relatively dry habitats. Libellula quadrimaculata is
a very widespread species in Latvia, and often is recorded at distances from water bodies in dry
70