J Syst Evol ›› 2008, Vol. 46 ›› Issue (6): 836-846.DOI: 10.3724/SP.J.1002.2008.08044

• Research Articles • Previous Articles     Next Articles

Ants pollinate Neottia listeroides (Orchidaceae) in Sichuan, China

14Chun-Qiu WANG; 13Yi-Bo LUO*; 2Yong-Dong TAI; 2De-Jun AN; 2Yong KOU   

  1. 1(State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China)
    2(Huanglong Administration of National Scenic Spot, Huanglong, Sichuan 624000, China)
    3(The National Orchid Conservation Center, Shenzhen 518114, China)
    4(Graduate University of Chinese Academy of Sciences, Beijing 100049, China)
  • Received:2008-04-03 Published:2008-11-18

Abstract: Ant-plant interaction is widespread, common and diverse in terrestrial ecosystems, but ants acting as pollinators are uncommon. Here we present a study conducted in Huanglong Nature Reserve, Sichuan, China, showing that ants of Formicidae, Leptothoras sp. and Paratrechina sp., are principle pollinators of Neottia listeroides (Orchidaceae). The two ant species accounted for dominant floral visitors and transferred most pollinia in the orchid, compared to the role of other insect visitors. The flowering period of N. listeroides in the studied population lasted about 40 days, and most flowers were open from 15th to 26th July. The flower has an open nectariferous furrow on the surface of the labellum which ran down the centre to the bifurcation of the labellum, and produced the minute amount of nectar. While an ant arrived at the base of the labellum following the nectariferous furrow, it could not touch the crest of the rostellum and withdraw the pollinia until it raised its head upwards. Pollinia were often attached to the top of the ant head by the viscid fluid exuded from the touched crest of the rostellum. After being touched the rostellum bent down instantly and blocked the stigma, and then slowly recovered to its original position. The backward movement of the rostellum lasted 17–24 h (21.4±2.1 h, n=42). The temporary inaccessi-bility of the stigma decreased self-pollination resulting from revisiting of ants. Breeding system experiments showed that this orchid is self-compatible but not autogamous, and that pollination success was dependent on pollinators. The fruit set was 19.77% under natural conditions, indicating that the efficiency of this ant-pollination system is low relative to the high frequency of visitation of ants. The low pollination success of N. listeroides was considered as a result of poor match in morphology between flowers and ants. Moreover, the interaction between N. listeroides and these two ants in Huanglong Valley was suggested as a casual case in a specific period.

Key words: Neottia listeroides, nectar, movement of the rostellum, ants pollination, pollination efficiency