Determining the extinction risk of poorly known species is difficult, as data on both their biological traits and the threats to which they are exposed are often not available. Neotropical freshwater stingrays (potamotrygonins) represent such a challenge, as limited ecological data prevent formal assessments. Geographic range size (GRS) was computed for the first time for potamotrygonins (as a longitudinal extent of occurrence measured in km of river length) and, together with two other traits correlated with intrinsic susceptibility to extinction—body size, biological productivity (r_max)—was used to rank potamotrygonins according to their intrinsic susceptibility to extinction. Potamotrygonin GRS was only 6%–7% of that of marine elasmobranchs and is likely to be a significant driver of potamotrygonin extinction risk. The relationship between potamotrygonin GRS and body size differed from the expected triangular theoretical pattern; probably a result of the fragmented nature of freshwater habitats. Using K-medoids clustering, we identified seven groups of species; the most susceptible groups comprised the biggest species such as Potamotrygon brachyura and Paratrygon spp. Intrinsic susceptibility was also highest in the largest hydrographic basins, likely as a result of species with low r_max being more common there. Exposure to anthropogenic threats is highest for the species most intrinsically susceptible to extinction, which consequently have a high-extinction risk. We recommend the use of longitudinal extents of occurrence as standardized measurements of freshwater taxa GRS. Our ranking method, combining observed and predicted traits, may be a useful tool to assess poorly known taxa to assist conservation prioritization.

中文翻译：

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在生态信息很少的情况下估计灭绝的内在敏感性：以新热带淡水黄貂鱼为例（软骨鱼目：Potamotrygoninae）

确定鲜为人知的物种的灭绝风险很困难，因为通常无法获得有关其生物特征和所面临威胁的数据。新热带淡水黄貂鱼（potamotrygonins）代表了这样一个挑战，因为有限的生态数据阻碍了正式评估。首次计算了动三角菌素的地理范围大小（GRS）（以河流长度公里为单位测量的纵向发生范围），以及与灭绝的内在易感性相关的其他两个特征——体型、生物生产力（r _max）——用于根据其对灭绝的内在敏感性对其进行排序。袖珍鱼 GRS 仅为海洋软骨鱼类的 6%–7%，可能是袖珍鱼灭绝风险的重要驱动因素。动三角蛋白GRS与体型之间的关系与预期的三角理论模式不同；可能是淡水栖息地支离破碎的结果。使用 K-medoids 聚类，我们确定了七组物种；最易受影响的群体包括体型最大的物种，如短眼子菜属 (Potamotrygon brachyura)和副鲆属 ( Paratrygon spp)。在最大的水文流域中，内在敏感性也最高，这可能是由于r _max较低的物种在那里更为常见。对于本质上最容易灭绝的物种来说，受到人为威胁的程度最高，因此具有很高的灭绝风险。我们建议使用纵向发生范围作为淡水类群 GRS 的标准化测量。我们的排名方法结合了观察到的和预测的特征，可能是评估鲜为人知的类群以协助保护优先顺序的有用工具。