Different pollinator assemblages ensure reproductive success of Cleisostoma linearilobatum (Orchidaceae) in fragmented holy hill forest and traditional tea garden

Abstract

Orchids are generally recognized to have specialist pollination systems and low fruit set is often thought to be characteristic of the family. In this study, we investigated the reproductive ecology of Cleisostoma linearilobatum, an epiphytic tropical orchid, in a holy hill forest fragment and a traditional tea garden in SW China using comparable methods. C. linearilobatum is self-compatible and dependent on insects for pollination. Fruit production in natural conditions was both pollinator- and resource-limited. However, the natural fruit set remained stable over multiple years at both sites. Pollination observations showed that C. linearilobatum has a generalized pollination system and seven insect species were observed as legitimate pollinators. Although the visit frequencies of different pollinators were different in the two sites, the pollinator assemblages ensured reproductive success of C. linearilobatum in both study sites over multiple years. The results partly explain why C. linearilobatum is so successful in the area, and also suggest that holy hill forest fragments and traditional tea gardens in Xishuangbanna are important in preserving orchids, especially those with generalist pollination.

Figure 1. Two study sites, inflorescence, flower and different visitors of Cleisostoma linearilobatum.

(a) The holy hill forest (HHF) is fragmented by modern tea monocultures; (b) The traditional tea garden (TTG) with many native shade trees; (c) Inflorescence; (d) Flower; (e) Eumenes sp.1; (f) Prionyx sp.; (g) Megachile dimidiate; (h) Amegilla yunnanensis; (i) Vespa sp.; (j) Apis sp.; (k) Eumenes sp. 2.

Figure 2. Floral longevity of Cleisostoma linearilobatum in different treatments.

Statistically homogeneous groupings based on a one-way ANOVA are indicated by the same letter (a–c) above the bars.

Figure 3. Mean visiting frequency of different pollinators to flowers of Cleisostoma linearilobatum in a holy hill forest (HHF) and a traditional tea garden (TTG) in different years.

Statistically homogeneous groupings based on one-way ANOVA are indicated by the same letter (a–c).