Systematics ofPseudorchis albida s.l.(Orchidaceae) in Europe and North America

Abstract

In ScandinaviaPseudorchis albida(Orchidaceae)s.l.is usually divided into the lowland and subalpineP. albida s.s.and the more or less alpineP. straminea.There have been some uncertainties and conflicting views concerning the taxonomic treatment of these taxa. To address this issue, herbarium specimens ofP. albida s.l.were studied for variation in morphological characters. A small-scale population study approach was used, as herbarium sheets with two or three plants were used as population samples. Canonical Variates Analysis (CVA) indicated a distinction between taxa in population means, corresponding toP. albida s.s.andP. straminea, respectively. Principal Components Analysis (PCA), however, revealed an overlap between individuals of the two taxa. The PCA analysis, furthermore, revealed that the overlap was considerably larger in material from Central Europe than in material from Fennoscandia. Studentt-tests on separate characters confirmed the picture, with more characters significantly different in Fennoscandian than in Central European material. Furthermore, a Tukey–Kramer test revealed that there were small differences between regional populations ofP. albida s.s., while there were several significant differences in single characters between the North American regional population ofP. straminea, as compared with the Central European and Fennoscandian regional populations. In Central Europe there is no clear separation between taxa, while in Fennoscandia the taxa are more clearly separated. This probably means that there is a difference in the time of establishment in the different regions. The author suggests a distinction of taxa at the subspecies level, and argues that the clear distinction seen in Fennoscandian material is due to separate immigration histories for the two subspecies into Fennoscandia after the last period of glaciation.