Odonata - Entomological Society of Latvia - Latvijas Daba

2. MATERIAL AND METHODS
Basic data. All freely available Latvian dragonfly observation data are included in the
dragonfly locality data base (created in Microsoft Office Access). The basic unit of a record is an
observation of a species in one location in one day. The data base includes:
• all published data, data collected by the author of this thesis and by other authors - 81
publication;
• author’s own unpublished data collected between 1991 and 2010 - 3498 entries;
• unpublished data collected by entomologists before 2011 - 1595 entries;
• data from museums and collections - five significant Latvian dragonfly collections;
• data from four websites and untested data of various observers, including nature management
plans of specially protected natural areas data - 847 entries;
• separate project and study data - 14 data sources.
All data sources are enlisted in a separate publication (Kalniņš 2012d). The data base includes
data regarding the place, where the species were found, date, number of individuals, sex, the stage
of development, brief information about the habitat, the observer or the source of publication/data,
the person who has identified the species and additional notes. The total amount of data to
31.12.2010 is 12065 entries from year 1778 to 2010.
2.1. RESEARCH OF THE CHANGES IN DRAGONFLY FAUNA AND DISTRIBUTION IN LATVIA
Changes in the faunistic composition. For faunistic analysis dragonfly species complying
with the following criteria were chosen:
• species are mentioned in literature as probable for Latvia;
• borders of the distribution area or separate localities are relatively close to the territory of
Latvia (Estonia, Europe part of Russia, Belarus, Lithuania and for several species - Poland;
literature data) or they are known as species that faster disperse in northern direction;
• species were recorded for the first time in Latvia during the last 20 years.
The distance from Latvia to its closest locality of the species was calculated by measuring the
closest distance from the locality to the border of Latvia. The distribution of southern species
recorded in Latvia earlier (Спурис 1951) in northern direction was calculated by measuring the
difference of latitude degrees (not certain localities!) between the historically northernmost locality
and the newest northernmost locality (recorded in the last 20 years). All distances were measured by
using Google Earth software. Besides that, an unsystematic inspection of the potential habitats and
identification of specimens were checked in the collections.
Species distribution maps were created using the Latvian geodetic co-ordinate system of the
5x5 km square system of 1992 and the topographic map system (TM-1993) of 1993 (Ģeotelpiskās...
2010).
The data included in the data base are subdivided in two categories (periods) - historical data
(1778 - 1990) and modern data (1991 - 2010). The species distribution maps have been created
using Arc GIS 9 software package. For each species the occupied squares in the historic and
modern period have been enlisted. The relative distribution % have been estimated for each species
in each period (the number of known occupied squares in the period /the number of all studied
squares in period x 100 %) (Bernard et al. 2009). The species distribution has been characterized in
the scale of five classes, based on the relative distribution of the species – occupied squares vs. all
surveyed squares:
6. very common - frequency of occupied squares >25.1%;
7. common - frequency of occupied squares 15.1-25.0;
8. moderately represented - frequency of occupied squares 5.1-15.0;
9. localized - frequency of occupied squares 1.1-5.0;
10. very rare - frequency of occupied squares 0.1-1.0.
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