Abstract
Dendrobium wangliangii is an epiphytic orchid distributed in the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, China. Most Dendrobium spp. typically have a low fruit set, but this orchid shows a higher fruit set under natural conditions despite the lack of effective pollinators. The pollination biology of the critically endangered D. wangliangii was investigated in this study. A fruit set rate of 33.33 ± 4.71% was observed after bagging treatment in 2017 and a high fruit set rate (65.72 ± 4.44% in 2011; 50.79 ± 5.44% in 2017) was observed under natural conditions, indicating that D. wangliangii is characterized by spontaneous self‐pollination. The anther cap blocked the growing pollinium; thus, the pollinium slid down and reached the stigmatic cavity, leading to autogamous self‐pollination. Specifically, 51.50% of 162 unopened flowers (total 257 flowers) of this Dendrobium species under extreme water‐deficit conditions developed into fruits, suggesting the presence of cleistogamy in D. wangliangii. Here, cleistogamy may represent the primary mode of pollination for this orchid. Spontaneous self‐pollination and specific cleistogamous autogamy could represent major adaptions to the drought and pollinator‐scarce habitat in the Jinshajiang dry‐hot valley.
Highlights
The floral diversity and pollination biology of Orchidaceae have long intrigued evolutionary biologists (Cozzolino & Widmer, 2005)
Dendrobium wangliangii, a recently de‐ scribed species of Dendrobium (Hu, Long, & Jin, 2008), endemic to the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, and found at an altitude of 2,200 m, is an epiphytic orchid with strong drought tolerance (Zhao et al, 2013, 2018). Studies on this plant in the wild observed that the rate of fruit set of D. wangliangii was rather high under natural conditions
The fruit set rate under spontaneous self‐pollination reached to 33.33%, which suggested that D. wangliangii displayed the trait of autonomous self‐pollination
Summary
The floral diversity and pollination biology of Orchidaceae have long intrigued evolutionary biologists (Cozzolino & Widmer, 2005). Between 5% and 20% of orchid species have evolved autogamy (Gale, 2007; Pang et al, 2012; Tremblay, Ackerman, Zimmerman, & Calvo, 2005) This mode of autogamy often occurs under windless conditions and in drought and insect‐scarce habitats to ensure reproductive success (Liu et al, 2006). Dendrobium wangliangii, a recently de‐ scribed species of Dendrobium (Hu, Long, & Jin, 2008), endemic to the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, and found at an altitude of 2,200 m, is an epiphytic orchid with strong drought tolerance (Zhao et al, 2013, 2018) Studies on this plant in the wild observed that the rate of fruit set of D. wangliangii was rather high under natural conditions. | 12907 mating system does D. wangliangii possess? and (b) If the species ex‐ hibits self‐pollination, what type of pollination strategy is employed?
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