Lin Shang-Yang, Chou Lien-Siang, Di Giusto Bruno, Bain Anthony
Institute of Ecology and Evolutionary Biology, College of Life Science, National Taiwan University, Rm. 635, Life Science Building, #1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan.
Journalism and Mass Communication Department, International College, Ming Chuan University, 250 Zhong Shan N. Rd., Taipei 111, Taiwan.
Bot Stud. 2015 Dec;56(1):32. doi: 10.1186/s40529-015-0113-7. Epub 2015 Nov 30.
Timing of reproductive events has become central in ecological studies linking success in pollination and seed dispersion to optimizing the probability and periods of encounters with pollinators or dispersers. Obligate plant-insect interactions, especially Ficus-fig wasp mutualisms, offer striking examples of fine-tuned encounter optimization as biological cycles between mutualistic partners are deeply dependent on each other and intertwined over generations. Despite fig flowering phenology being crucial in maintaining Ficus-fig wasp mutualisms, until now, the forces of selection shaping the phenological evolution of dioecious fig trees have received little attention. By conducting a 2-year survey of a population of Ficus benguetensis in Northern Taiwan, we assessed whether environmental factors or other selective pressures shape the phenology of male and female fig trees.
Constraints by mutualistic pollinating wasps and seed dispersers, rather than climatic factors, appeared to mainly shape fig phenology and allometry in F. benguetensis. We identified a new sexual specialization in dioecious fig trees: the position of fig production. We propose that the continuous male fig production on tree trunks can enhance the survival of pollinating fig wasps through faster localization of receptive figs while reducing the mutualistic conflict between the fig and its obligate pollinators. By contrast, in female trees, fig production is massive in summer, located on the twigs of the foliar crown and seem more related to seed dispersal and germination.
Identifying variations in the allometry and phenology of dioecious figs provide valuable insights into how monoecious and dioecious species resolve mutualism conflicts and into the emergence of dioecy in fig trees.
在将授粉和种子传播的成功与优化与传粉者或传播者相遇的概率和时期联系起来的生态学研究中，生殖事件的时间安排已成为核心内容。专性的植物 - 昆虫相互作用，特别是榕树 - 榕小蜂共生关系，提供了微调相遇优化的显著例子，因为共生伙伴之间的生物周期相互高度依赖且代代交织。尽管榕树的开花物候在维持榕树 - 榕小蜂共生关系中至关重要，但到目前为止，塑造雌雄异株榕树物候进化的选择力量很少受到关注。通过对台湾北部的孟加拉榕种群进行为期两年的调查，我们评估了环境因素或其他选择压力是否塑造了雄树和雌树的物候。
在孟加拉榕中，共生传粉榕小蜂和种子传播者的限制，而非气候因素，似乎主要塑造了榕树的物候和异速生长。我们在雌雄异株榕树中发现了一种新的性别特化：榕果产生的位置。我们提出，树干上持续产生雄榕果可以通过更快地定位可接受的榕果来提高传粉榕小蜂的存活率，同时减少榕果与其专性传粉者之间的共生冲突。相比之下，在雌树上，榕果在夏季大量产生，位于叶冠的嫩枝上，似乎与种子传播和萌发更相关。
确定雌雄异株榕树的异速生长和物候变化，为雌雄同株和雌雄异株物种如何解决共生冲突以及榕树中雌雄异株现象的出现提供了有价值的见解。
