Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, 560012, India.
Department of Biology (Ecology and Evolutionary Biology), University of Toronto Mississauga, Mississauga, ON, Canada.
Oecologia. 2024 May;205(1):215-227. doi: 10.1007/s00442-024-05566-3. Epub 2024 May 27.
Mutualisms are consumer-resource interactions, in which goods and services are exchanged. Biological market theory states that exchanges should be regulated by both partners. However, most studies on mutualisms are one-sided, focusing on the control exercised by host organisms on their symbionts. In the brood-site pollination mutualism between fig trees and their symbiont wasp pollinators, galled flowers are development sites for pollinator larvae and are exchanged for pollination services. We determined if pollinator galls influenced resource allocation to fig inflorescences called syconia and considered feedbacks from the host tree. We experimentally produced syconia containing only seeds (S), only pollinator galls (G) or seeds and galls (SG) with varying number of introduced female pollinator wasps, i.e., foundress wasps. Biomass allocation to syconia was affected by foundress numbers and treatment groups; SG treatments received highest biomass allocation at low foundress numbers, and both G and SG treatments at high foundress numbers. Seeds are important determinants of allocation at low foundress numbers; galls are likely more influential at high foundress numbers. Most allocation in the G and SG treatment was to the syconium wall, likely as protection from parasitoids and temperature/humidity fluctuations. Dry mass of individual seeds and wasps (except at low foundress numbers) was unchanged between treatment groups, indicating seeds and wasps regulate resource flow into them, with lower flow into galls containing the smaller males compared to females commensurate with sexual dimorphism. We demonstrate the importance of considering the direct role of symbionts in accessing resources and controlling exchanges within mutualisms.
互利共生是消费者-资源相互作用，其中商品和服务被交换。生物市场理论表明，交换应该受到双方的控制。然而，大多数互利共生的研究都是片面的，侧重于宿主生物对其共生体的控制。在榕果和它们的共生传粉蜂之间的繁殖地传粉互利共生中，受瘿花是传粉蜂幼虫的发育场所，并被用来换取传粉服务。我们确定了传粉蜂瘿是否影响了榕果称为榕果的资源分配，并考虑了来自宿主树的反馈。我们通过实验产生了只含有种子的榕果（S）、只含有传粉蜂瘿的榕果（G）或含有不同数量引入的雌性传粉蜂（即，育母蜂）的种子和瘿的榕果（SG）。生殖果的生物量分配受育母蜂数量和处理组的影响；在育母蜂数量低的情况下，SG 处理组获得的生物量分配最高，而在育母蜂数量高的情况下，G 和 SG 处理组都获得了最高的生物量分配。种子是低育母蜂数量下分配的重要决定因素；瘿在高育母蜂数量下可能更具影响力。G 和 SG 处理组中的大多数分配都给了榕果壁，这可能是为了防止寄生虫和温度/湿度波动的影响。在处理组之间，单个种子和蜂的干质量（除了育母蜂数量低的情况）没有变化，这表明种子和蜂调节资源流入它们的流量，与较小的雄性相比，流入雌性的流量较低，这与性二型性相一致。我们证明了考虑共生体在获取资源和控制互利共生中交换方面的直接作用的重要性。
