Seed natural enemies and tropical forest diversity

在物种丰富的热带森林中，天敌在构建和维持植物多样性方面的作用正日益得到认识。迄今为止，研究几乎完全集中在从母植物、幼苗和较大植物（如1,2,3）传播后攻击种子的敌人上。最近，一些备受瞩目的研究表明，这种扩散后的捕食为热带森林的高度多样性提供了一种机制。传播前种子敌人的潜在作用，即在种子传播之前攻击种子的敌人，几乎被完全忽视了(5)。一个潜在的重要的预传播种子敌人群体是内部取食的昆虫种子捕食者（通常是鞘翅目，鳞翅目），它们以树冠中的种子为食，在这个过程中杀死它们。我们在巴拿马的巴罗科罗拉多岛的研究表明，大多数树种都受到了种子捕食者的攻击。我们还知道，这些天敌对寄主具有高度的特异性，只有20%的昆虫种子捕食者以一种以上的寄主植物为食。这使得这些昆虫成为一个有趣和相关的进一步研究群体。例如，如果它们倾向于在寄主丰富的地方杀死大部分种子，它们就有可能在群落水平上促进植物物种的共存（6,7）。本项目的目的是评估传播前昆虫种子捕食者对单个植物物种和更广泛的植物群落水平的影响。更具体地说，学生将能够1)研究预扩散昆虫种子捕食对单个树木的适应性后果；2)评估敌人造成的传播前种子死亡率的时空和群落水平变化；3)观察到的模式对植物群落水平上物种共存的潜在影响。该项目还将评估观察到的高（bbb50 %）水果过早脱落与预分散敌人攻击之间的联系。该学生将有机会获得由一位导师和她的合作者收集的数据集，这些数据集是之前研究的一部分，包括大约500种植物的昆虫种子捕食者在社区层面的攻击模式信息，以及Barro Colorado岛上数百种植物的30年种子雨数据。该学生将接受有关这些数据集的统计分析和建模的培训，以解决传播前种子死亡率对种群和群落动态的作用。还将有可能对巴罗科罗拉多岛的个别植物物种进行实地研究（观察研究、实验）。该项目有可能对一组研究较少的植物敌人产生新的见解。考虑到最近人们对热带森林昆虫数量下降的关注，这个研究主题尤其具有话题性(8)，而且范围更广。

The role of natural enemies in structuring and maintaining plant diversity in species-rich tropical forests is being increasingly recognised. To date, research has focused almost exclusively on enemies attacking seeds after dispersal from the mother plant, seedlings, and larger plants (e.g. 1, 2, 3). Recent, high-profile (4) work has shown that this post-dispersal predation provides a mechanism for the hyperdiversity of tropical forests. The potential role of pre-dispersal seed enemies, i.e. enemies attacking seeds prior to seed dispersal, has been almost completely ignored (5). One potentially important group of pre-dispersal seed enemies are the internally-feeding insect seed predators (typically Coleoptera, Lepidoptera) that feed on seeds in the canopy, killing them in the process. Our work on Barro Colorado Island in Panama shows that the majority of tree species are attacked by pre-dispersal seed predators. We also know that these enemies are highly host-specific, with only 20% of insect seed predator species feeding on more than one host plant species. This makes these insects an interesting and relevant group for further study. For example, if they tend to kill a large proportion of seeds where their host is abundant, they have the potential to promote the coexistence of plant species at the community level (6, 7). The aim of this project is to assess the impacts of pre-dispersal insect seed predators on individual plant species and at the wider plant community level. More specifically, the student will be able to 1) investigate the fitness consequences of pre-dispersal insect seed predation for individual trees; 2) assess spatial, temporal, and community-level variation in rates of enemy-inflicted pre-dispersal seed mortality, and 3) the potential implications of observed patterns on species coexistence at the plant community level. The project will also 4) assess the link between observed high (>50%) levels of premature fruit abscission and pre-dispersal enemy attack. The student will have access to data sets collected as part of previous research conducted by one of the supervisors and her collaborators, including information on community-level patterns of attack by insect seed predators across ~500 plant species and >30 years of seed rain data for hundreds of plant species on Barro Colorado Island. The student will receive training in statistical analysis of these data sets and modelling to address the role of pre-dispersal seed mortality on population and community dynamics. There will also be possibilities for field-based research (observational studies, experiments) on individual plant species on Barro Colorado Island. The project has the potential to yield novel insights into a poorly studied group of plant enemies. The research theme is particularly topical given recent concerns about declining insect populations in tropical forests (8), and more widely.