Abstract. Tanghe, M. & Lefebvre, C.- Mean term dynamics of a spontaneous population of Dactylorhiza fuchsii (DRUCE) Soo in a suburban garden. [Natural. belges 91 (Orchid. 23) (2010): 29-46]. A single plant of Dactylorhiza fuchsii, a rare orchid species in Belgium, appeared spontaneously in a suburban garden and flowered for the first time in 2003. Surprisingly, owing its isolation, it gave rise to a juvenile population as early as 2005. Its evolution has been followed for five years by means of pointed mapping, counting fertile plants, flower and capsule production, as well as measuring adult height, spike length and stem diameter. Taking into account the geographic isolation of the mother plant, these data provide information about the demographic success of this nectarless orchid. It is assumed that the relative decrease in growth performance of the offspring compared with the mother plant could be due to inbreeding depression.

 

Key-Words: Orchidaceae; European orchids, Dactylorhiza fuchsii, population biology and dynamics, reproductive success, inbreeding depression.