Bio-Protection Research Centre, Lincoln University , Lincoln , Christchurch , New Zealand.
Université d'Angers , Angers , France.
PeerJ. 2014 Feb 25;2:e262. doi: 10.7717/peerj.262. eCollection 2014.
Only recently has it been formally acknowledged that native species can occasionally reach the status of 'pest' or 'invasive species' within their own native range. The study of such species has potential to help unravel fundamental aspects of biological invasions. A good model for such a study is the New Zealand native scarab beetle, Costelytra zealandica (White), which even in the presence of its natural enemies has become invasive in exotic pastures throughout the country. Because C. zealandica still occurs widely within its native habitat, we hypothesised that this species has only undergone a host range expansion (ability to use equally both an ancestral and new host) onto exotic hosts rather than a host shift (loss of fitness on the ancestral host in comparison to the new host). Moreover, this host range expansion could be one of the main drivers of its invasion success. In this study, we investigated the fitness response of populations of C. zealandica from native and exotic flora, to several feeding treatments comprising its main exotic host plant as well as one of its ancestral hosts. Our results suggest that our initial hypothesis was incorrect and that C. zealandica populations occurring in exotic pastures have experienced a host-shift rather than simply a host-range expansion. This finding suggests that an exotic plant introduction can facilitate the evolution of a distinct native host-race, a phenomenon often used as evidence for speciation in phytophagous insects and which may have been instrumental to the invasion success of C. zealandica.
直到最近，人们才正式承认，在其本土范围内，本地物种偶尔也会成为“害虫”或“入侵物种”。对这些物种的研究有可能帮助我们揭示生物入侵的一些基本方面。新西兰本土的金龟子 Costelytra zealandica（White）就是一个很好的研究模型，尽管它有天敌，但在全国的外来牧场中还是已经变得具有入侵性。由于 C. zealandica 在其本土栖息地仍广泛存在，我们假设该物种仅经历了宿主范围的扩展（即在祖先宿主和新宿主上同样使用的能力），而不是宿主转移（与新宿主相比，在祖先宿主上适应性降低）。此外，这种宿主范围的扩展可能是其成功入侵的主要驱动因素之一。在这项研究中，我们调查了来自原生和外来植物的 C. zealandica 种群对几种喂养处理的适应能力，这些处理包括其主要的外来宿主植物以及其一个祖先宿主。我们的研究结果表明，我们最初的假设是错误的，即在异国牧场中出现的 C. zealandica 种群经历了宿主转移，而不仅仅是宿主范围的扩展。这一发现表明，外来植物的引入可以促进一个独特的本地宿主种族的进化，这种现象经常被用作植食性昆虫物种形成的证据，并且可能对 C. zealandica 的入侵成功起到了重要作用。
