Enemy release, biotic resistance and the success of invasive forest insects

我的研究旨在通过更好地了解影响天敌调控森林昆虫的因素，提高我们管理森林昆虫的能力。具体地说，我探讨了与昆虫天敌的种群死亡率和群落多样性有关的问题，重点是了解和操纵本土寄生蜂和捕食者。最近引入加拿大的几种主要森林昆虫(翡翠白蜡虫、亚洲天牛、天牛)使我们能够比较本地和外来天敌的复合体，并探索这些群落影响寄主死亡和害虫入侵的机制。我目前的工作测试了关于外来物种和群落如何取代本地物种的假说，以便更好地了解森林中的入侵过程。在这个提案中，我测试了敌人释放假说(ERH)，更具体地说，是敌人减少非本土物种假说(ENRS)。我提出的问题是，ENRS是否解释了敌人对本土(IPS)和外来(Tomicus)树皮甲虫的攻击和寄主生产力的模式，或者是否有证据表明存在生物抗性(BR)。东部松材线虫(P.pini)原产于北美，而另一种以韧皮部为食的节肢动物是在1990年代的S时期从欧洲引进的。后者已经确立；两者都是共生的，在安大略省南部的林分中以相同的本地松树(P.strobus，P.resinosa，P.bansiana)和外来的松树(P.cervestris)为食。利用这个外来/本土的树皮甲虫系统，我将测试ERN在这两种甲虫上的捕食水平、寄生性以及敌人和同伙的群落多样性。我预测，本土甲虫的天敌将比非本土甲虫更多样化，发生密度也更大。生物地理和致癌数据将通过甲虫密度的梯度得出，以量化天敌的存在程度，并考虑甲虫的死亡率和生产力。这些结果将加深我们目前对入侵动态的了解，并在应用水平上帮助指导入侵外来森林昆虫物种的管理策略。

My research aims to increase our ability to manage forest insects through improved understanding of factors that affect natural enemies regulating forest-feeding insects. Specifically, I explore questions related to population mortality and community diversity of insect natural enemies, with focus on understanding and manipulating native parasitoids and predators. Recent introductions into Canada of several major forest insects (emerald ash borer, Asian long-horned beetle, Sirex woodwasps) enables us to compare the complexes of native and exotic natural enemies, and to explore mechanisms by which these communities affect host mortality and pest invasion. My current work tests hypotheses about how exotic species and communities displace native ones in order to better understand invasion processes in the forest. In this proposal, I test the enemy release hypothesis (ERH), more specifically, the enemy reduction in nonindigenous species hypothesis (ENRS). I ask the questions, does ENRS explain patterns of enemy attack and host productivity on indigenous (Ips) and exotic (Tomicus) bark beetles, or is there evidence for biotic resistance (BR). The eastern pine engraver beetle (I. pini) is native to NA, while T. piniperda (another phloem-feeding scolytid) was introduced from Europe during the 1990's. The latter has become established; both are sympatric and feed on the same native (P. strobus, P. resinosa, P. banksiana) and exotic (P. sylvestris) pines in stands across southern Ontario. Using this exotic/indigenous bark beetle system, I will test ERNS with respect to levels of predation, parasitism, and community diversity of enemies and associates on these two beetles. I predict that enemies of the indigenous beetle will be more diverse and occur at greater densities than those of the nonindigenous Tomicus. Biogeographic and ontongenic data will be derived across a gradient of beetle densities to quantify the degree to which enemies are present, and account for beetle mortality and productivity. These results will add to our current understanding of invasion dynamics, and at the applied level, help to direct management strategies for invasive alien forest insect species.