Macdonald A J, Jackson D, Zemenick K
School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA.
Environ Entomol. 2013 Aug;42(4):658-67. doi: 10.1603/EN12287.
Fungal entomopathogens are widely distributed across natural and managed systems, with numerous host species and likely a wide range of community impacts. While the potential for fungal pathogens to provide biological control has been explored in some detail, less is known about their community interactions. Here we investigate the effects of fungal epizootics of the entomopathogen Lecanicillium lecanii (Zimmerman) on a keystone mutualism between Azteca instabilis (F. Smith), a dominant arboreal ant, and the green coffee scale (Coccus viridis Green), as well as broader impacts on a coffee agroecosystem ant community. We hypothesized that seasonal epizootics cause shifts in the foraging ranges of A. instabilis as the ants adapt to the loss of the resource. We further hypothesized that the magnitude of these shifts depends on the availability of alternate resources located in neighboring shade trees. To test these hypotheses, we induced an epizootic in experimental sites, which were compared with control sites. Surveys of ant activity were undertaken pre- and post-epizootic. We found a decrease in foraging activity of A. instabilis and increase in activity of other ant species in the experimental sites post-epizootic. The decrease in abundance of A. instabilis foragers was greater on plants in which an epizootic was induced than in other plants. This relationship was modified by shade tree density where higher shade tree density was associated with larger decreases in A. intabilis foraging activity in coffee plants. These results demonstrate the potential for fungal entomopathogens to influence the structure and diversity of ecological communities.
真菌性昆虫病原体广泛分布于自然和人工管理系统中，宿主种类繁多，可能对群落产生广泛影响。虽然真菌病原体提供生物防治的潜力已得到一定程度的详细研究，但对它们的群落相互作用了解较少。在此，我们研究昆虫病原体蜡蚧轮枝菌（Lecanicillium lecanii，齐默尔曼）的真菌流行病对不稳定阿兹特克蚁（Azteca instabilis，F. 史密斯）（一种优势树栖蚂蚁）与绿咖啡豆蚧（Coccus viridis，格林）之间关键共生关系的影响，以及对咖啡农业生态系统蚂蚁群落更广泛的影响。我们假设季节性流行病会导致不稳定阿兹特克蚁的觅食范围发生变化，因为蚂蚁会适应资源的损失。我们进一步假设这些变化的幅度取决于相邻遮荫树中替代资源的可用性。为了验证这些假设，我们在实验地点诱发了一场流行病，并与对照地点进行比较。在流行病前后对蚂蚁活动进行了调查。我们发现，在实验地点，流行病发生后不稳定阿兹特克蚁的觅食活动减少，其他蚂蚁物种的活动增加。在诱发了流行病的植物上，不稳定阿兹特克蚁觅食者数量的减少幅度大于其他植物。这种关系因遮荫树密度而改变，遮荫树密度越高，咖啡植物中不稳定阿兹特克蚁觅食活动的减少幅度就越大。这些结果表明，真菌性昆虫病原体有可能影响生态群落的结构和多样性。
