Abstract
The lady’s slipper orchid (Cypripedium calceolus), which inhabits shady deciduous and mixed forests and meadows, is now threatened with extinction in many European countries, and its natural populations have been dramatically declining in recent years. Knowledge of its evolutionary history, genetic variability, and processes in small populations are therefore crucial for the species’ protection. Nowadays, in south-west Poland, it is only distributed in seven small remnant and isolated populations, which we examined. One nuclear (ITS rDNA) and two plastid (accD-psa1, trnL-F) markers were analyzed and compared globally in this study. Based on the nuclear marker, the most common ancestor of C. calceolus and Cypripedium shanxiense existed about 2 million years ago (95% HPD: 5.33–0.44) in Asia. The division of the C. calceolus population into the European and Asian lineages indicated by C/T polymorphism started about 0.5 million years ago (95% HPD: 1.8–0.01). The observed variation of plastid DNA, which arose during the Pleistocene glacial–interglacial cycles, is still diffuse in Poland. Its distribution is explained by the result of fragmentation or habitat loss due to human impact on the environment.
Highlights
Cypripedium calceolus is a rare, long-lived, terrestrial, and allogamous orchid species with a horizontal rhizome [1,2,3]
The C. calceolus evolutionary lineage was formed about 2 million years ago in Asia (C. shanxiense and other closely related species are found there). This time falls in the Pleistocene period, in which progressive glaciation could have contributed to the geographical isolation of the ancestor of both species
The C allele is characteristic of European and Asian populations (Western Russia, Siberia) [20], while the T allele occurs both in Europe and in Siberia and the Russian Far East [20], as well as in Korea and Japan
Summary
Cypripedium calceolus (the lady’s slipper orchid or yellow lady’ slipper) is a rare, long-lived, terrestrial, and allogamous orchid species with a horizontal rhizome [1,2,3]. It is a boreal species that occurs in shady deciduous and mixed woodland (rarely in full sunlight) and meadows, predominantly on calcareous soils [3,4]. This orchid is regarded as a species of least concern according to the International Union for Conservation of Nature (IUCN) [5]. In some countries, including Poland, it is listed in the red list and red books as a threatened species [6] because it is critically endangered [2,7,8,9]. This situation may be mainly explained by climate changes, habitat destruction and alternation, as well as improper forest management [5,9,13]
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