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The Asian genus Struckia Mü ll.Hal. is reduced to a synonym of Plagiothecium Bruch & Schimp. according to a phylogenetic analysis involving S. argentata (Mitt.) Mü ll.Hal., S. enervis (Broth.) Ignatov, T.J.Kop. & D.G.Long and 13 representative boreal species of Plagiothecium. Two nuclear regions, ITS and partial gapC, and five chloroplast regions, rbcL, rps4-trnS, psaB, trnG and trnL-F, were utilized to reconstruct the phylogenetic relationship between Struckia and Plagiothecium. Bayesian, maximum parsimony, and maximum likelihood analyses resulted in a strongly supported clade including Struckia and Plagiothecium. Plagiothecium handelii Broth. and P. paleaceum (Mitt.) A.Jaeger, which share similar geographical ranges with Struckia and intermediate morphological traits between Struckia and Plagiothecium, grouped with the Chinese Struckia, and all of them appeared as sister to the 'core' of Plagiothecium. The accurate position of P. piliferum (Sw.) Schimp. remains unclear due to moderate support from all analyses, and we suggest that it is retained in Plagiothecium until further evidence is available.

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Genetic distance is used to classify and elucidate the evolutionary relationship between populations, such as species, which have been diverging for a long period. The properties of genetic distance measures in livestock classi®cation have hitherto not been investigated. We used simulation studies to compare the accuracy of eight genetic distance measures to classify recently diverged populations. The effect of varied population sizes from generation to generation were also taken into account. Comparatively better results are obtained from Nei's standard distance with two alleles at each locus and from Nei's D A distance with four alleles at each locus under various conditions. However, the difference in accuracy among distance measures was small and very high correlations were shown. The number of alleles at each locus had a greater effect on accuracy than the number of loci or type of distance measures. It indicates that highly polymorphic markers, such as DNA microsatellite, are powerful tool to improve the accuracy in classi®cation of domestic animals. The six distance measures had a linear relationship with generation number at constant population size. None of the distance measures, however, showed a linear relationship when population size varied. The effect of¯uctuating population size on the average distance was obvious over the ®rst few generations but declined when the number of generations was increased. ZusammenfassungGenetische Distanz und Klassi®zierung von Haustieren mittels genetischer Marker Genetische Distanzen werden verwendet, um evolutiona Ère Beziehungen zwischen Populationen, die vor langer Zeit divergierten, einzuordnen und aufzukla Èren. Die Eigenschaften der hierfu È r verwendeten Maûeinheiten wurden bislang bei Haustieren noch nicht untersucht. Es wurden Simulationsmodelle verwendet, um die Genauigkeit von 8 Distanzmaûen fu È r ku È rzlich divergierte Populationen miteinander zu vergleichen. Dabei wurde der Effekt sich vera Èndernder Populationsgro È ûen miteinbezogen. Die im Vergleich besten Ergebnisse wurden mit Nei's Standard-Distanz mit zwei Allelen je Locus und mit Nei's D A ± Distanz mit 4 Allelen je Locus unter verschiedenen Bedingungen erzielt. Die Unterschiede in der Genauigkeit war zwischen den Distanzmaûen gering und sehr hohe Korrelationen konnten nachgewiesen werden. Die Anzahl der Allele je Locus hatte einen gro È ûeren Ein¯uss auf die Genauigkeit als die Anzahl der Loci oder das Distanzmaû. Dies zeigt, dass hochpolymorphe Marker wie DNA-Mikrosatelliten schlagkra Èftige Instrumente sind, um die Genauigkeit der Klassi®zierung von Haustieren zu verbessern. Die sechs Distanzmaûe hatten bei konstanter Populationsgro È ûe eine lineare Beziehung mit der Generationenzahl. Bei variierender Populationsgro È ûe zeigte allerdings keines der Distanzmaûe eine lineare Beziehung. Der Ein¯uss variierender Populationsgro È ûen auf die durchschnittliche Distanz war wa Èhrend der ersten Generationen offensichtlich, verringerte sich aber bei steigender Generationenzahl.