The ecology of leeches worldwide has been scarcely studied, with the ecology of Neotropical leeches remaining highly unknown. Americobdella valdiviana, an endemic, carnivorous, and giant leech that inhabits the Valdivian evergreen forest in southern Chile, an ecosystem that has experienced an increase in its net loss from 3.6% to 12% in the last decades due to various human activities. Here, we combined citizen science with species distribution models (SDM) to analyze (i) the effect of habitat variables with the abundance A. valdiviana, (ii) the distribution range, (iii) the habitat loss and fragmentation of A. valdiviana, and (iv) their conservation status. First, we asked each user or scientist for the observed relative abundance and a series of environmental variables, which were then correlated by using Generalized Linear Models. Then, distribution ranges were estimated using SDM, which was combined with multiannual forest cover maps to identify habitat loss and fragmentation between 2000 and 2018. Finally, we used IUCN criteria to evaluate the conservation status of this species. Abundance was related mainly to the canopy coverage, while suitability was positively associated to temperature seasonality and canopy cover. Suitability was higher in forests with levels of primary productivity. We found that the north and center zones of the species range experienced high habitat loss and fragmentation. Under IUCN Red List criteria, we qualified this species as endangered. Our results support that the combination of citizen science, SDM, and spatial analysis at local and biogeographical scales can inform conservation actions of poorly known and threatened macroinvertebrate fauna.

世界范围内水蛭的生态学研究很少，新热带水蛭的生态学仍然高度未知。Americobdella valdiviana是一种地方性、食肉和巨型水蛭，栖息在智利南部瓦尔迪维亚常绿森林中，由于各种人类活动，该生态系统的净损失在过去几十年中从 3.6% 增加到 12%。在这里，我们将公民科学与物种分布模型 (SDM) 相结合来分析 (i) 栖息地变量对A. valdiviana丰度的影响，(ii) 分布范围，(iii) A. valdiviana的栖息地丧失和破碎化，以及 (iv) 它们的保护状态。首先，我们询问每个用户或科学家观察到的相对丰度和一系列环境变量，然后使用广义线性模型将它们关联起来。然后，使用 SDM 估计分布范围，并结合多年森林覆盖图来识别 2000 年至 2018 年间的栖息地丧失和破碎化。最后，我们使用 IUCN 标准来评估该物种的保护状况。丰度主要与冠层覆盖率有关，而适宜性与温度季节性和冠层覆盖率呈正相关。初级生产力水平的森林的适宜性更高。我们发现该物种范围的北部和中部地区经历了严重的栖息地丧失和破碎化。根据 IUCN 红色名录标准，我们将这个物种定性为濒危物种。我们的结果支持公民科学、SDM 和地方和生物地理尺度空间分析的结合可以为鲜为人知和受威胁的大型无脊椎动物群的保护行动提供信息。