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Coexistence and population genetic structure of the whooper swan Cygnus cygnus and mute swan Cygnus olor in Lithuania and Latvia IntroductionCoexistence between closely related species in a given habitat or region has been of interest to researchers for decades [1][2][3][4]. Species with diverse population structures are generally better adapted to changing environmental conditions and can more successfully utilize new types of habitats [5]. As a result of global environmental change, closely related species that were historically separated by geographic barriers are sometimes found to coexist, which can result in an increase in interactions such as competition and hybridization. Two closely related swan species, the mute swan Cygnus olor and the whooper swan Cygnus cygnus were formerly allopatric throughout their breeding ranges, but during the last decades their breeding ranges have overlapped in the Baltic Sea Region [6][7][8]. This range overlap was caused by a rapid expansion in the breeding range of both species in Europe. In Lithuania and Latvia both species presently occur in the same type of habitats.The whooper swan is a characteristic species of the boreal zone in Europe. It was pushed close to extinction in the Baltic region during the 19 th and the early 20 th century due to intense human persecution [6]. A rapid range expansion of the species has been recorded since the 1970s (mainly due to improved conservation measures) and during the past decades it has established as a breeding species in all countries of the Baltic region. In Sweden, the number of whooper swans has increased from 20 pairs in the early 20 th century to about 5.400 pairs estimated during the last few years [9]. Similarly in Finland, a recorded 15 pairs from the 1940s have increased to 5.000-7.000 pairs during the last decade [10]. An increase in the number of the breeding birds was also recorded in other countries of Central and Western Europe [11][12][13][14][15][16]. The species continues to spread southwards, re-occupying former nesting grounds. During the same period, since the Keywords: Cygnus cygnus • Cygnus olor • D-loop • population genetic structure • CoexistenceAbstract: Two closely related swan species, the mute swan Cygnus olor and the whooper swan Cygnus cygnus, were formerly allopatric throughout their breeding ranges, but during the last decades a sympatric distribution has become characteristic of these species in the Baltic Sea region. The whooper swan has gradually replaced the mute swan in many suitable habitats in Lithuania and Latvia. Marked differences in the genetic population structure of both species may partially explain the dominance of the whooper swan, as genetic population divergence can be a major factor affecting inter-specific competition. A homogenous genetic population structure was defined for mute swans breeding in Lithuania, Latvia, Poland and Belarus. Breeding mute swans in this region are mostly of naturalised origin. A diverse population genetic structure characterizes whooper swans bree...

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Genetic Differentiation of Dabbling Ducks (Anseriformes: Anas) Populations From Palaearctic in Time and Space The genetic variation among populations of dabbling ducks (563 samples of A. acuta, A. clypeata, A. crecca, A. querquedula, A. falcata, A. penelope, A. platyrhynchos) in the Palaearctic region (Lithuania, Chukotka, Kamchatka, Lena, Ob and Kara rivers) was investigated between 1980 and 1998. Fifteen loci of blood serum proteins were surveyed for genetic variation using polyacrylamid gel electrophoresis, and eight polymorphic loci were found. The analysis of genetic variation at population and species levels shows that allele frequencies are temporarily variable. The general genetic diversity of dabbling ducks differed among geographically different populations: for Northern Pintail between Ho = 0.264 from Ob river and Ho = 0.331 from Kamchatka; for Eurasian Wigeon between Ho=0.185 from Ob and Ho = 0.263 from Lena river. In Mallard populations mean heterozygosity ranged from Ho = 0.242 (Vente 1998, Lithuania) to Ho = 0.366 (Antanavas 1987, Lithuania). The data obtained from genetic distances revealed that Mallards of Lithuania form no discrete populations and vary temporarily and spatially.

The tufted duck (Aythya fuligula, Anatidae) is widespread in the Palaearctic across Northern Eurasia. Birds breeding in Northern and Eastern Europe are highly migratory, while populations from Western Europe are partially migratory or resident. The aim of this study is to explore genetic variation within and between ducks breeding in Latvia and migrants sampled in North West Russia and Belarus. The technique of random amplified polymorphic DNA was applied using five random primers (ol-1, ol-9-12). Genetic variability was measured for all tufted ducks investigated and for different sub-populations from various regions. Individual genetic structure and genetic variability was higher in ducks collected from Latvia. Gene diversity of amplified DNA bands in birds of Latvian origin was 24% with 80% polymorphism. Means of gene diversity and polymorphism for tufted ducks sampled in other countries varied from 12 to 14% and from 27 to 40%, respectively. A high number of unique bands characterized ducks breeding in Latvia. The oligonucleotide primers used in this study were suitable to analyze differences among tufted ducks of different origin. Possible explanations for the variation observed among the studied ducks are discussed.