Xia J, Sun S G, Guo Y H
Laboratory of Plant Systematics and Evolutionary Biology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.
Plant Biol (Stuttg). 2007 Nov;9(6):713-9. doi: 10.1055/s-2007-965259. Epub 2007 Sep 21.
There has been substantial debate in recent years surrounding the impact of introduced honeybees on native biota. This study reports on an investigation of Pedicularis densispica, a subalpine annual herb endemic to Southwest China, in an attempt to determine the impact of introduced domestic honeybees on pollen dispersal and thus on their reproductive success and mating system. Honeybees were introduced into the study site in 2004, and a sudden seasonal pollinator shift from bumblebees to honeybees was observed. Intra- and inter-plant visits by different pollinators were recorded in the field in 2003 and 2004. Fruit and seed sets prior to and after the pollinator shift were measured. Experimental pollinations were performed to characterize the breeding system. Outcrossing rates at the seed stage were estimated for both years using RAPD markers. Our results indicated that honeybees foraged between plants more frequently than bumblebees did. Our results also revealed that the introduction of honeybees significantly enhanced reproductive success. However, no significant difference was detected between the outcrossing rates due to bumblebee and honeybee pollination. P. densispica was almost completely outcrossing ( T(m) = 0.956 and 0.967, respectively in 2003 and 2004) but partially self-compatible. This study presents the first report of the outcrossing rate in the genus pedicularis and reveals a limited influence of pollination on the mating system in P. densispica. The pollinator shift did not reduce reproductive success of the plants and honeybees may be used to augment pollinator services for nectariferous P. densispica.
近年来，围绕引进蜜蜂对本地生物群的影响一直存在大量争论。本研究报告了对中国西南地区特有的亚高山一年生草本植物密穗马先蒿的一项调查，旨在确定引进的家养蜜蜂对花粉传播的影响，进而确定其对繁殖成功率和交配系统的影响。2004年蜜蜂被引入研究地点，观察到传粉者出现了从熊蜂到蜜蜂的季节性突然转变。2003年和2004年在田间记录了不同传粉者在植株内和植株间的访花情况。测量了传粉者转变前后的果实和种子结实率。进行了实验授粉以表征其繁育系统。利用RAPD标记估计了这两年种子阶段的异交率。我们的结果表明，蜜蜂在植株间觅食的频率比熊蜂更高。我们的结果还表明，蜜蜂的引入显著提高了繁殖成功率。然而，未检测到熊蜂授粉和蜜蜂授粉导致的异交率之间存在显著差异。密穗马先蒿几乎完全异交（2003年和2004年的T(m)分别为0.956和0.967），但部分自交亲和。本研究首次报道了马先蒿属的异交率，并揭示了授粉对密穗马先蒿交配系统的影响有限。传粉者转变并未降低植株的繁殖成功率，蜜蜂可用于增加对产蜜密穗马先蒿的传粉服务。
