Genetic diversity, compatibility patterns and seed quality in isolated populations of Cypripedium calceolus (Orchidaceae)

摘要

Cypripedium calceolus has suffered an alarming decline, and today mainly occurs in small and isolated populations. In Denmark there are only two populations, close to each other and situated far from other European stands. One population is stagnant or in slow decline, whereas the other is in rapid increase. We examined the levels of genetic diversity and compatibility and seed quality following experimental crosses. No genetic variation could be detected in plastid and nuclear markers within or between the two populations—in contrast to results previously reported from other European populations of C. calceolus. This may indicate a founder effect in both populations, but it could also be the outcome of prolonged inbreeding or reflect a genetic bottleneck after the populations were established. According to fruit dimensions and frequency of fully developed seeds there was full self-compatibility in the stagnant population, and partial late-acting self-incompatibility in the proliferating population. In combination with previous reports from other countries, this suggests that several self-incompatibility systems may occur in C. calceolus. Seeds from the older and stagnant population performed more poorly in germination tests in vitro than seeds from the thriving population. The difference needs not be genetically based, but could be due to environmental differences during seed maturation, producing different seed quality or dormancy characteristics. However, low level of genetic diversity within the populations may affect their ability to adapt and the possibility of inbreeding depression should be investigated.