CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 51 No. 2 June 2002
The contribution of nonindigenous Cercopagis pengoi (Ostroumov) in the mesozooplankton community and its population structure in the Gulf of Riga; 91–102
Abstract. The nonindigenous predatory cladoceran Cercopagis pengoi forms a permanent population in the whole Gulf of Riga. During the investigation period 1997–99, the density of C. pengoi showed an increasing tendency with the highest recorded abundance (5790 ind. m–3) in the littoral zone. Maximum values were often found in the eastern part of the Gulf, where the highest water temperatures and lower salinities were recorded. Total zooplankton abundances were higher in the south-eastern and central parts of the Gulf. C. pengoi densities were higher above the thermocline, where over 50% of the population consisted of juveniles, than beneath it. In the warm upper water layers (0–4 m) juveniles formed up to 92% of the total population density. Presence of C. pengoi in the littoral zone seems to be unfavourable for microzooplanktonic rotatorians and nauplii of copepods.
Key words: Baltic Sea, Gulf of Riga, mesozooplankton, Cercopagis pengoi, population structure, nonindigenous species.
Phylogenetic analysis of cetrarioid lichens with globose ascospores; 103–123
Andres Saag, Tiina Randlane, Arne Thell, and Walter Obermayer
Abstract. The group of cetrarioid lichens with globose ascospores includes 37 species from eight genera. Phylogenetic analysis, using program PAUP 3.1.1, was carried out on two different data sets – morphological (incl. anatomical and chemical) and molecular characters (ITS1, 5.8S, and ITS2 rDNA sequences) – to verify the correspondence of current taxonomy to the probable evolution of the taxa involved. The paraphyletic nature of the genus Allocetraria in regard to two species of Dactylina is assumed based on morphological characters. Still, the separation of these genera is strongly supported by the analysis of molecular data. The genus Tuckermannopsis (11 species) is paraphyletic in regard to Esslingeriana idahoensis and “Nephromopsis” weii. Monophyletic origin can be declared only for the Tuckermannopsis ciliaris group. The analysis based on molecular characters exhibits the monophyletic origin of the group including three Tuckneraria species. Monophyly of the genus Ahtiana was not supported by the analysis of morphological data.
Key words: cetrarioid lichens, Parmeliaceae, Ahtiana, Allocetraria, Dactylina, Esslingeriana, “Nephromopsis” weii, Tuckneraria, Tuckermannopsis, Vulpicida, ITS rDNA sequences, cladistic analysis.
New records of aphids (Homoptera, Aphidodea) from Estonia; 124–137
Abstract. According to the literature reports 185 species of aphids (Homoptera, Aphidodea) have been found in Estonia. In this paper additional material on 55 aphid species new to Estonia is presented. From species new to Estonia Aphis forbesi Weed, A. newtoni Theob., A. praeterita Wlk., Anuraphis catonii H.R.L., Brachycaudus tragopogonis (Klt.), Dysaphis bonomii (H.R.L.), and D. devecta (Wlk.) probably have the northern border of their distribution area here. Macrosiphum trollii Börn. is a boreoalpine species. It has been found in Finland but not in Latvia and Lithuania.
Key words: Homoptera, Aphidodea, Estonia, new records.
The lack of old-growth forest – a threat to Estonian biodiversity; 138–144
Abstract. Between 1997 and 2000, forest structure was studied in random plots in a 900-km2 area in east-central Estonia. Only 2.4% (1.2% outside reserves) of forest land was covered by old unmanaged multi-cohort forests or forests with gap-phase dynamics, and 28% of their area was situated in edge zones. No stands naturally recovering after a recent natural stand-replacing disturbance were found. Hence, Estonian forest landscapes seem to lack habitats for old-growth specialists, and restoration of natural structure of forests may be needed for the viability of the most sensitive species.
Key words: conservation, extinction threshold, forest edge, natural forests, Estonia.