Seed dispersal in six species of terrestrial orchids in Biebrza National Park (NE Poland)

Abstract

Knowledge about seed dispersal is required to explain problems in ecology, phylogeography, and conservation biology. Even though seed dispersal is a fundamental mechanism to understand problems at different levels of biological organization (individual, population, species, landscape), it remains one of the least recognized processes. Similar to other groups of plants, very little is known regarding patterns and distances of seed dispersal in orchids. Orchid seeds are generally assumed to be widely dispersed by wind because of their small size and low weight. Between 2006 and 2008, we conducted a field study of the distances at which orchid seeds are dispersed, and determined factors affecting dispersal. Investigations included 13 populations of six terrestrial orchid species -Cypripedium calceolus, Cephalanthera rubra, Epipactis helleborine, Goodyera repens, Neottia ovata, and Platanthera bifolia. To evaluate seed dispersal in orchid populations, 8.5-cm Petri dishes (traps) with self-adhesive paper were placed along transects, starting from a group of fruiting plants, which were considered to be the dispersal source. Seeds of the investigated orchid species were dispersed over relatively short distances. There were statistically significant negative correlations between seed density and distance from the fruiting plants. Seeds of species with taller fruiting shoots were dispersed farther than those with shorter ones (R = 0.68, p < 0.05). We discuss the causes and consequences of the dispersal patterns of orchid seeds.

Seed dispersal and realized gene flow of two forest orchids in a fragmented landscape

“…Jersakova & Malinova (2007) found reduced dispersal of Dactylorhiza majalis seed in taller vegetation of a wet meadow compared to short turf vegetation. Similarly, Brzosko et al (2017) reported a negative effect of height of surrounding plants as well as physical barriers caused by local relief on Platanthera bifolia seed dispersal in a forest. The dense understorey in the pine forest could reduce air movement in comparison with the beech forest in this study.…”

“…However, this assumption is not fully supported by recent experimental germination studies, showing that seeds may often germinate at unoccupied sites (de Hert et al 2013), and that suitable symbiotic fungi are more widespread than the initial mycoheterotrophs (reviewed in McCormick & Jacquemyn 2014). In addition, seed trapping studies showed that most of the dust‐like seeds land very close to the maternal plants, and maximum reported distance is between 0.8 and 15.5 m (Machon et al 2003; Jersakova & Malinova 2007; Johansson et al 2014; Brzosko et al 2017). Similar results were obtained with plant genotyping, where maximum estimated dispersal distance varied between 5 and 16 m (Chung et al 1998, 2004, 2005a, 2005b; Smouse & Peakall 1999).…”

“…Dispersal abilities of windborne seeds are influenced by wind dynamics and local conditions, such as habitat structure and continuity ( e.g. Damschen et al 2014; Heydel et al 2014; Brzosko et al 2017; Hemrova et al 2019). Dispersal efficiency may be decreased in the understorey of closed forests, where air turbulence and density of the canopy reduce the modal dispersal distance (Okubo & Levin 1989; Gabay et al 2012; Milleron et al 2012; Heydel et al 2014; Zhao et al 2016).…”

“…Dispersal efficiency may be decreased in the understorey of closed forests, where air turbulence and density of the canopy reduce the modal dispersal distance (Okubo & Levin 1989; Gabay et al 2012; Milleron et al 2012; Heydel et al 2014; Zhao et al 2016). Similarly, the height of vegetation surrounding the mother plant was found to negatively influence seed dispersal (Jersakova & Malinova 2007; Brzosko et al 2017).…”

Spatial genetic structure of an endangered orchid Cypripedium calceolus (Orchidaceae) at a regional scale: limited gene flow in a fragmented landscape

“…Gene flow, which often acts as a cohesive force in plant population, is rather negligible in C. calceolus due to constraints related to its pollination mechanisms, seed dispersal and germination. Fruit set is relatively low, frequently below 10% (Kull 1998;Nicole et al 2005;Pedersen et al 2012;Brzosko et al 2017b). Although long-distance dispersal of its dust-like seeds is expected to occur (Fay et al 2009), effective seed dispersal does not exceed 5 m (Brzosko et al 2017b).…”