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Comparative karyotype analysis of the Pseudotsuga genus Colangeli, Anna Maria


Numerical data were collected from the karyotypes of seven species in the Pseudotsuga genus, P. forrestii, P. sinensis, P. gaussenii, P. japonica, P. wilsoniana, P. macrocarpa and both varieties of P. menziesii, (Douglas-fir), menziesii and glauca. A comparative karyotype study was made utilizing chromosome number, secondary constrictions and chromosomal characteristics, to identify and separate the different species. Both varieties of Douglas-fir contained a somatic chromosome number of 2n=26 consisting of five metacentrics, six submetacentrics and two telocentric pairs. P. macrocarpa and the Asiatic species contained a somatic chromosome number of 2n=24 consisting of six metacentric and six submetacentric pairs. Douglas-fir could be identified by chromosome number. An analysis of variance and a multivariate stepwise discriminant function analysis were employed to test the validity of using karyotype data such as arm ratio, centromere index, morphological index and relative length for characterizing the cytogenetical and the geographical differences for each of the n=12 species. Good discrimination was shown among P. macrocarpa and the Asiatic species for both the analysis of variance and the multivariate analysis. The discrimination among the Asiatic species was further improved when the well separated P. macrocarpa was omitted. A high level of discrimination was observed between the two varieties of Douglas-fir by both the t-test and the multivariate analysis. The multivariate analysis was particularly helpful in selecting variables that best separated the taxa. To my knowledge, these results provide the first reported karyotype numerical analysis for the Pseudotsuga genus as well as the first reported karyotype analysis for P. gaussenii.

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