曼陀罗的生殖生物学：食草传粉者的益处
Reproductive biology of Datura wrightii: the benefits of a herbivorous pollinator.
作者信息
Bronstein Judith L, Huxman Travis, Horvath Brianna, Farabee Michael, Davidowitz Goggy
机构信息
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, USA.
出版信息
Ann Bot. 2009 Jun;103(9):1435-43. doi: 10.1093/aob/mcp053. Epub 2009 Mar 14.
BACKGROUND AND AIMS
A deeper understanding of mutualism can be reached by studying systems with measurable costs and benefits. Most studies of this type focus on an unusual class of obligate, species-specific pollination mutualisms. The interaction between Datura wrightii (Solanaceae) and the hawkmoth Manduca sexta offers similar advantages but greater generality. Adult moths both nectar at and deposit eggs on the same plant; larvae are herbivorous. The antagonistic component of this interaction has been well studied. Here the role of M. sexta as a pollinator of D. wrightii, particularly in the context of this moth's frequent nectaring visits to the bat-pollinated plant Agave palmeri, is documented.
METHODS
Hand-pollinations were used to determine breeding system and the reproductive consequences of mixed loads of A. palmeri and D. wrightii pollen. Plants and moths were caged overnight to assess whether nectaring visits led to fruit and seed set. Finally, pollen deposited on field-collected stigmas was identified, with a particular focus on documenting the presence of D. wrightii and A. palmeri grains.
KEY RESULTS
Datura wrightii is highly self-compatible, and a visit that deposits either outcross or self pollen almost doubles fruit and seed set compared with unvisited flowers. Manduca sexta transferred enough pollen to produce fruit and seed sets comparable to hand-pollination treatments. Agave palmeri did not interfere with D. wrightii success: in the field, stigmas received almost pure D. wrightii pollen, and hand-addition of large quantities of A. palmeri pollen had no measurable effect on fruit and seed set.
CONCLUSIONS
The floral visitation component of the D. wrightii-M. sexta interaction is indeed mutualistic. This finding is essential background to future development of this interaction as a model system for studying mutualism's costs and benefits. It is already proving valuable for dissecting third-species effects on the outcome of mutualism. Results indicate that M. sexta's heavy visitation to A. palmeri has no negative effect on the benefits conferred to D. wrightii. However, it can be predicted to augment M. sexta populations to the point where the costs of the interaction begin to exceed its benefits.
背景与目的
通过研究具有可衡量成本和收益的系统，可以更深入地理解共生关系。这类研究大多聚焦于一类不同寻常的专性、物种特异性传粉共生关系。曼陀罗（茄科）与烟草天蛾之间的相互作用具有相似的优势，但更具普遍性。成年蛾类既在同一植株上采蜜，也在其上产卵；幼虫为食草性。这种相互作用中的拮抗成分已得到充分研究。本文记录了烟草天蛾作为曼陀罗传粉者的作用，特别是在这种蛾类频繁拜访由蝙蝠传粉的植物帕尔玛龙舌兰的背景下。
方法
采用人工授粉来确定繁育系统以及帕尔玛龙舌兰和曼陀罗混合花粉负载的生殖后果。将植株和蛾类关在一起过夜，以评估采蜜拜访是否会导致结果和结籽。最后，鉴定沉积在野外采集的柱头上的花粉，特别关注记录曼陀罗和帕尔玛龙舌兰花粉粒的存在情况。
主要结果
曼陀罗具有高度的自交亲和性，与未受拜访的花朵相比，一次传递异交或自花花粉的拜访几乎使结果和结籽量增加一倍。烟草天蛾传递的花粉量足以产生与人工授粉处理相当的结果和结籽量。帕尔玛龙舌兰不会干扰曼陀罗的成功授粉：在野外，柱头上几乎接收到纯的曼陀罗花粉，大量添加帕尔玛龙舌兰花粉对结果和结籽量没有可测量的影响。
结论
曼陀罗 - 烟草天蛾相互作用中的访花成分确实是互利共生的。这一发现是未来将这种相互作用发展为研究共生关系成本和收益的模型系统的重要背景。它已被证明对于剖析第三物种对共生关系结果的影响很有价值。结果表明，烟草天蛾对帕尔玛龙舌兰的频繁拜访对曼陀罗获得的益处没有负面影响。然而，可以预测这会使烟草天蛾种群增加到相互作用的成本开始超过其收益的程度。
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