Invertebrates make a very diverse group of animals, which possesses just a few common features. These animals are only remotely related to each other and differ significantly by their size, form and lifestyle. Many invertebrates are found in water, but some groups live and are widespread on land. Carolus Linnaeus divided all invertebrates into 2 main groups: insects and worms.
Each year, new insect species for Latvia are discovered. The indication system for biological diversity of terrestrial ecosystems is being elaborated.
The results have been summarized in the book “The invertebrate (Invertebrata) fauna and ecology of the habitats of Slītere national park”. The book provides overall survey of the Slītere national park’s habitats and their characteristic invertebrates’ fauna und ecology. Publications about the invertebrate fauna of Slītere national park have been used, as well as the author’s personal investigations and observations, which have been made while guiding students’ field courses; also, the information provided by the author’s colleagues has been included.
Slītere national park is an especially protected natural area included in the Natura 2000 network of European protected areas. The oldest part of the territory has been established in 1921 by selecting a little-affected large tract of forest within an area of 1100 ha. In this territory, economical activities have not been performed already 80 years. The current territory of the park has been established in 2000. Its terrestrial area covers 16,360 ha, and marine aquatorium covers 10,130 ha.
In the field of entomology, ecological researches dominate.
In Latvia, researchers of invertebrates do not describe many new species; instead of it, more attention is paid to the ecological investigations involving the studies of flora and fauna of particular habitats. Just to mention a few, such investigations have been done in raised bogs, coastal habitats and low calcareous fens.
More than 1,000 insect species have been determined in raised (peat) bogs. Besides that, a third of these species live only in this habitat. That testifies about these species’ specialization to live in the harsh bog conditions. In 1999, about 600 ha of forests and bogs burned out in the Lielais Ķemeru tīrelis bog, which provided a great opportunity to begin investigations of the consequences of bog fire. It was observed that already in the first days after the fire species dependent on the fire emerged. In burning, some particular fungus species grow, which provide a specific food chain, which exist for about two years. Later on, bog’s vegetation and animal communities restore. After the fire, a rapid multiplication of some beetles – specialists of bog habitat – has been observed. At the landscape level, bog fire increases the diversity of species.
In the coastal areas, there are especially protected habitats called grey dunes. Investigations done in the dunes allowed to ascertain species – specialists of dune habitats. These specialist species can be used as indicator species for natural dunes, as well as show the influence of trampling down on this habitat. It has been clarified that the biggest threat to the dune habitats is their overgrowing with pines. In the Pāvilosta’s grey dune, pine trees were partially cut down to retain the initial vegetation and fauna. Insects – especially grasshoppers and other sand dwellers – served as one of the indicators of the management practices’ efficiency. Coastal habitats are inhabited not only by specific species, but also by random new-comers from inland’s habitats. Sometimes masses of insects are observed in the seaside. These are unsuccessful migrants. If warm wind blows from the land, it carries myriads of flying insects in the sea and then waves sometimes wash them ashore.
The most recent investigations have been done in low calciferous fens. These fens are especially protected areas. Until recently, entomologists did not want to make researches in these harsh habitats due to their wetness, as well as clouds of horseflies and mosquitoes and hot sun in summer. In recent researches, it has been ascertained that the diversity of species in these habitats is high, but the number of individuals is rather low. About one fourth of the species are specialized to live in low fens and are not found in other habitats. Characteristically, the highest diversity of species has been recorded in the periphery of bogs and fens, where species from nearby habitats can also live. In the center of bogs and fens, there is a higher proportion of specialist species. Bog and fen plants are not nourishing; very few insect species feed on sedges, bog-rushes, fen-sedges, bog-myrtles. One plant species – great fen-sedge – drastically diminishes the diversity of insect species, although from the botanists’ point of view the habitat formed by this plant is especially protected.
These are not the only investiagations done. Latvian entomologists-ecologists investigate also, for example, the influence of dead wood, colonies of cormorants, flooding of alluvial meadows, forest management, forest type and burning of heath on insect communities. Insects are very useful for such investigations because using them researchers can quickly obtain much of material and ascertain natural regularities.
