Variation in size-dependent fitness components in a terrestrial orchid, Dactylorhiza majalis (Rchb.) Hunt et Summerh., in relation to environmental factors

Abstract

We investigated the flowering probability and flower production in relation to plant size in a terrestrial orchid, Dactylorhiza majalis at 10 meadow sites in central and southwestern Poland. These sites differed in altitude (low, high) and management (presence or absence of mowing). At all sites, concentrations of nutrients in the soil were also measured. The probability of flowering increased significantly with the size of the plant in all populations, indicating that individuals do not flower until they reach a threshold size. Populations at high altitudes and the unmown sites had significantly lower threshold sizes for reproduction and showed sharp increase in flowering probability with plant size, compared to other populations. The threshold sizes for reproduction tended to decrease at sites rich in N and Mg and poor in P and S. Flower production was also size-dependent in all populations. Considerable between-site differences were found in the slope and the intercept of the regression between plant size and flower production. Flower production at some sites, at high altitudes, increased more steeply with plant size than at other sites. However, no pattern in size-dependent flower production was found relative to the measured environmental variables. Most of the size-dependent components of flowering probability were related to each other but not with the size-dependent flower production.

Demographic responses of boreal-montane orchid Malaxis monophyllos (L.) Sw. populations to contrasting environmental conditions

“…They very often exhibit fast responses to environmental changes, which is reflected mainly in decreases in abundances of local populations, as well in lowering their reproductive potential (e.g., [34][35][36][37]), which makes most orchid species relatively highly threatened. Moreover, high variations in demographic parameters over time and space are a property of orchids populations [38][39][40][41][42][43], and this is usually connected with differences in environmental and climatic conditions through geographical range of species, as well in differences in management [39,[44][45][46]. Intrinsic factors, however, like genetic variability, or population age and history have also a great importance, and are highlighted as factors significantly influencing within-population processes [47].…”