PDF(Pubmed)
Abstract：
Organismal invasions have repeatedly been cited as a driving force behind the loss of biodiversity. Unlike many other impacts of invasion, the effect of invasion on native symbiont communities has received less attention. The introduction of invasive hosts presents a potential opportunity to native symbionts; invasive hosts could benefit native symbionts through providing a novel host environment that improves symbiont fitness relative to their fitness on native hosts. Alternatively, invasive hosts could noncompetent hosts for native symbionts, resulting in negative impacts on native symbiont abundance and diversity. Crayfish in the northern hemisphere host diverse assemblages of obligate annelid symbionts (P: Anellida, O: Branchiobdellida). Two invasive crayfish hosts in the genus Faxonius have been introduced and are interacting with the native crayfish hosts and their symbionts in three watersheds in western Virginia, USA. Previous studies suggest that the invasive host F. cristavarius is a less competent host for symbionts compared to native hosts in the genus Cambarus. We carried out an extensive survey in these watersheds to determine impacts of varying degrees of invasion on branchiobdellidan abundance and diversity. We also conducted a complementary host replacement experiment to investigate how increases in the relative abundance of invasive hosts contributes to observed patterns of symbiont abundance and diversity in the field. In our survey, as the proportion of invasive hosts at a site increased, branchiobdellidan abundance and diversity declined significantly. In the experiment, the worms dispersed onto both native and invasive hosts. As the percentage of noncompetent F. cristavarius hosts increased, the survival of branchiobdellidans declined. Both symbiont survival and opportunities for successful dispersal are reduced as this noncompetent invasive host progressively displaces native hosts, which imperils the integrity of native host-symbiont systems. Given that many native hosts accrue significant fitness benefits from their relationships with native symbionts, including hosts in our study system, losses of beneficial symbionts may produce a positive feedback loop that decreases invasion resistance of native species, exacerbates the effects of invasions, and presents a major conservation issue in invaded systems.
摘要：
器官入侵一再被认为是生物多样性丧失的驱动力。与入侵的许多其他影响不同，入侵对原生共生生物群落的影响受到的关注较少。侵入性宿主的引入为原生共生体提供了潜在的机会；侵入性宿主可以通过提供一种新颖的宿主环境来使原生共生体受益，该环境相对于其在原生宿主上的适应度提高了共生体的适应度。或者，侵入性宿主可能是原生共生体的无能宿主，对原生共生体的丰度和多样性产生负面影响。北半球的小龙虾拥有不同的专性环状共生体组合（P：Anellida，O:Branchiobdellida)。引入了Faxonius属的两个入侵性小龙虾宿主，并与弗吉尼亚西部三个流域的本地小龙虾宿主及其共生体相互作用，美国。先前的研究表明，与Cambarus属的天然宿主相比，侵入性宿主F.cristavarius是共生体的能力较差的宿主。我们对这些流域进行了广泛的调查，以确定不同程度的入侵对枝条丰度和多样性的影响。我们还进行了互补的宿主替代实验，以研究侵入性宿主相对丰度的增加如何有助于该领域观察到的共生体丰度和多样性模式。在我们的调查中,随着一个站点上侵入性宿主比例的增加，branchiobdellidan的丰度和多样性显着下降。在实验中,蠕虫散布在原生和侵入性宿主上。随着不称职的克里斯塔瓦利斯宿主的百分比增加，branchiobdellidans的存活率下降。随着这种无能力的侵入性宿主逐渐取代天然宿主，共生生物的生存和成功扩散的机会都会减少，这损害了本地宿主-共生体系统的完整性。鉴于许多本地宿主从与本地共生体的关系中获得了显着的健身益处，包括我们学习系统中的宿主，有益共生体的损失可能会产生正反馈回路，从而降低本地物种的入侵抗性，加剧了入侵的影响，并提出了入侵系统中的主要保护问题。
