Leech-derived iDNA complements traditional surveying methods, enhancing species detections for rapid biodiversity sampling in the tropics

Deforestation, exploitation, and other drivers of biodiversity loss in Madagascar leave its highly endangered and predominantly endemic wildlife at risk of extinction. Decreasing biodiversity threatens to compromise ecosystem functions and vital services provided to people. New, economical, and diverse methods of biodiversity monitoring can help to establish reliable baseline and long-term records of species richness. Metabarcoding with invertebrate-derived DNA (iDNA) has emerged as a promising new biosurveillance tool. An unexpected wet forest fragment tucked in the dry cliffs of Madagascar's southcentral plateau, the Ivohibory Protected Area (IPA), hosts a unique mosaic of species diversity, featuring both dry and wet forest species. Recently elevated to protected status, the IPA has been surveyed for flora and fauna with a range of inventory methods over three years and six expeditions (2016, 2017, & 2019). We collected 1,451 leeches over 12 days from the IPA to supplement known species richness and to compare results against current records. With iDNA, we pooled tissues, and isolated, and amplified bloodmeal DNA with five sets of primers. We detected 20 species of which four are species of frogs previously undetected and three of which are previously unknown to exist in this region. iDNA surveys can provide complementary data to traditional surveying methods like camera traps, line transects, and bioacoustic methods.马达加斯加的森林砍伐、资源开发及其他生物多样性丧失驱动因子，使其极度濒危且以特有物种为主的野生动物面临灭绝风险。生物多样性的持续下降，还会损害生态系统功能及为人类提供的关键生态服务。新型、经济且多元的生物多样性监测方法，有助于建立可靠的物种丰富度基线与长期观测记录。基于无脊椎动物源DNA（invertebrate-derived DNA, iDNA）的元条形码（metabarcoding）技术，已成为颇具应用前景的新型生物监测工具。坐落于马达加斯加中南部高原干旱崖壁中的一处意外发现的湿润森林片段——伊沃希博里保护区（Ivohibory Protected Area, IPA），拥有独特的物种多样性镶嵌格局，同时栖息着干旱林与湿润林物种。该保护区近年刚被列入保护名录，研究团队在三年间开展了六次野外考察（2016、2017及2019年），采用多种调查方法对其动植物进行了全面普查。本研究团队于12天内从该保护区采集了1451只水蛭，用以补充已知的物种丰富度数据，并将研究结果与现有记录进行对比分析。我们借助iDNA技术，将组织样本混匀后，利用5对引物完成了血餐DNA的分离与扩增。本次检测共发现20个物种，其中4种蛙类为此前未被记录的新物种，另有3种为该区域此前未有分布记录的物种。iDNA监测可作为红外相机陷阱法、样线法及生物声学监测法等传统调查手段的补充数据来源。