Beaulieu C, Lavoie C, Proulx R. 2018. Bookkeeping of insect herbivory trends in herbarium specimens of purple loosestrife (Lythrum salicaria).

The potential use of herbarium specimens to detect herbivory trends is enormous but largely untapped. The objective of this study was to reconstruct the long-term herbivory pressure on an invasive plant, purple loosestrife (<i>Lythrum salicaria</i>), by evaluating leaf damages over 1323 specimens from southern Québec (Canada). Historical trends suggest a gradual increase in hole feeding and margin feeding damages from 1883 to around 1940, followed by a period of relative stability. The percentage of specimens with window feeding damages did not begin to increase until the end of the 20th century, from 3% (2 ̶ 6%) in 1990 to 45% (14 ̶ 81%) in 2015. Temporal changes in the frequency of window feeding damages support the hypothesis of an increasing herbivory pressure by recently introduced insects. This study shows that leaf damages made by insects introduced for the biocontrol of purple loosestrife, such as coleopterans of the <i>Neogalerucella</i> genus, can be assessed from voucher specimens. Herbaria are a rich source in information that can be used to answer questions related to plant-insect interactions in the context of biological invasions and biodiversity changes.

利用标本馆馆藏标本（herbarium specimens）探究植食性昆虫取食趋势的潜力巨大，但目前尚未得到充分开发。本研究旨在通过评估加拿大魁北克南部1323份标本的叶片受害情况，重建入侵植物紫花千屈菜（purple loosestrife，学名<i>Lythrum salicaria</i>）的长期植食压力。历史趋势显示，1883年至1940年左右，食孔型取食与叶缘型取食造成的叶片受害程度呈逐渐上升趋势，随后进入相对稳定阶段。窗斑型取食受害标本的占比直至20世纪末才开始上升，从1990年的3%（2%~6%）升至2015年的45%（14%~81%）。窗斑型取食受害频率的时间变化趋势，支持了“新近传入的昆虫导致植食压力上升”这一假说。本研究表明，可通过馆藏凭证标本，评估用于紫花千屈菜生物防治的外来昆虫（如新亮叶甲属<i>Neogalerucella</i>鞘翅目昆虫）造成的叶片受害情况。标本馆蕴藏着丰富的信息资源，可用于解答生物入侵与生物多样性变化背景下的植物-昆虫互作相关科学问题。