Abstract This is the first study documenting the distribution and population biology of the Endangered Aloe lettyae, an endemic to the highly threatened Woodbush Granite Grassland (WGG) in Limpopo Province, South Africa. We documented 19 A. lettyae populations and calculated the total area of occupied habitat at 17.5 ha within its extent of occurrence of 123 km2. Most populations were clustered on the south western side of the WGG, with all known localities less than 40 km apart in this severely fragmented vegetation type. Population size varied from 10 to 6547 plants, with ∼10,800 individuals estimated in total. Plant size and life history stage demographics were determined in seven of the 19 currently known A. lettyae populations, including two large populations, as well as a high- and a low-lying population, and constituted a representative sample of the entire geographical range of the species. For plant size, four metrics (number of leaves, number of leaf layers, height and diameter of the leaf rosette) were recorded for each sampled A. lettyae plant, and the presence of an inflorescence indicated its reproductive status. By means of the classification tree technique CHAID (Chi-square Automatic Interaction Detection), we determined that of the four plant size metrics, the ‘number of leaves’ predicts A. lettyae’s life history stages and fecundity most accurately, and revealed significant differences in the life history stage structure of the seven surveyed populations. Five populations occurring in relatively undisturbed WGG fragments, including the two large populations, comprised high proportions of adult individuals (77–89%), while only few A. lettyae juveniles were found (3–14%). By contrast, the relatively high percentage of juveniles (25–58%) and low percentage of adults (32–63%) observed in two small populations found in a degraded WGG fragment and in non-natural habitat respectively, appeared atypical. The percentage of subadults varied little across the surveyed populations (8–13%). In slow-growing, long-lived species such as A. lettyae, the dominance of adult individuals with a high probability of survival may be considered as indicative of stable populations. This study provides baseline A. lettyae population data for long-term demographic monitoring which will aid management and conservation of the range restricted, Endangered A. lettyae.

中文翻译：

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悬在那里：极度濒危草原碎片中的芦荟种群

摘要 这是第一项记录濒危芦荟分布和种群生物学的研究，芦荟是南非林波波省高度受威胁的伍德布什花岗岩草原 (WGG) 的特有种。我们记录了 19 个 A. lettyae 种群，并计算了其发生范围 123 平方公里内 17.5 公顷的栖息地总面积。大多数种群聚集在 WGG 的西南侧，所有已知地点都在这种严重破碎的植被类型中相距不到 40 公里。种群大小从 10 到 6547 株植物不等，估计总共约有 10,800 个人。在目前已知的 19 个 A. lettyae 种群中的 7 个中确定了植物大小和生活史阶段的人口统计数据，包括两个大种群，以及一个高地和低地种群，并构成了该物种整个地理范围的代表性样本。对于植物大小，记录了每个采样的 A. lettyae 植物的四个指标（叶数、叶层数、叶莲座的高度和直径），并且花序的存在表明其生殖状态。通过分类树技术 CHAID（卡方自动交互检测），我们确定了四种植物大小指标中，“叶子数”最准确地预测了 A. lettyae 的生活史阶段和繁殖力，并揭示了显着差异7个被调查人群的生活史阶段结构。出现在相对未受干扰的 WGG 片段中的五个种群，包括两个大种群，成年个体的比例很高（77-89%），而只有少数 A. 发现了 lettyae 幼鱼 (3–14%)。相比之下，分别在退化的 WGG 片段和非自然栖息地中发现的两个小种群中观察到的相对较高百分比的幼鱼 (25-58%) 和低百分比的成鱼 (32-63%) 显得不典型。受调查人群中亚成体的百分比变化不大（8-13%）。在生长缓慢、寿命长的物种中，例如 A. lettyae，具有高存活概率的成年个体的优势可被视为种群稳定的指标。本研究为长期人口监测提供基线 A. lettyae 种群数据，这将有助于管理和保护范围受限的濒危 A. lettyae。分别在退化的 WGG 片段和非自然栖息地中发现的两个小种群中观察到的相对较高百分比的幼鱼 (25-58%) 和低百分比的成鱼 (32-63%) 似乎不典型。受调查人群中亚成体的百分比变化不大（8-13%）。在生长缓慢、寿命长的物种中，例如 A. lettyae，具有高存活概率的成年个体的优势可被视为种群稳定的指标。本研究为长期人口监测提供基线 A. lettyae 种群数据，这将有助于管理和保护范围受限的濒危 A. lettyae。分别在退化的 WGG 片段和非自然栖息地中发现的两个小种群中观察到的相对较高百分比的幼鱼 (25-58%) 和低百分比的成鱼 (32-63%) 似乎不典型。受调查人群中亚成体的百分比变化不大（8-13%）。在生长缓慢、寿命长的物种中，例如 A. lettyae，具有高存活概率的成年个体的优势可被视为种群稳定的指标。本研究为长期人口监测提供基线 A. lettyae 种群数据，这将有助于管理和保护范围受限的濒危 A. lettyae。受调查人群中亚成体的百分比变化不大（8-13%）。在生长缓慢、寿命长的物种中，例如 A. lettyae，具有高存活概率的成年个体的优势可被视为种群稳定的指标。本研究为长期人口监测提供基线 A. lettyae 种群数据，这将有助于管理和保护范围受限的濒危 A. lettyae。受调查人群中亚成体的百分比变化不大（8-13%）。在生长缓慢、寿命长的物种中，例如 A. lettyae，具有高存活概率的成年个体的优势可被视为种群稳定的指标。本研究为长期人口监测提供基线 A. lettyae 种群数据，这将有助于管理和保护范围受限的濒危 A. lettyae。