The giant panda (Ailuropoda melanoleuca) is the most basal living species in the phylogeny of the family Ursidae, with a specialized diet composed of a variety of bamboo species. The evolutionary history and past distribution patterns of the giant panda remain poorly understood. Our aim was to integratively apply distinct methods to evaluate the evolutionary history and distributional patterns of the giant panda; these included phylogeography, ecological niche modeling (ENM), and fossil data. To this end, we characterized the panda’s past and present ecological niches and the environmental conditions that define them. To estimate the panda’s phylogeographic patterns and the environmental conditions (precipitation and temperature) available across its historical geographic range, we evaluated its past distribution during the Last Glacial Maximum (LGM). Considering that modeling biotic interactions (e.g., foraging, predation) is still an enormous challenge, we propose a novel modeling strategy based on the panda’s specialized diet, using an ensemble of three bamboo genera with distribution across the panda’s historical geographic range. Finally, we tested the accuracy of our approach by evaluating its ability to predict the LGM fossils. Our results support that the panda’s diversification across its distribution happened ca. 2.7 million years (Mya), coinciding with the likely period when the panda changed from a carnivorous to a vegetarian diet (from the Pleistocene to the Pliocene), acquiring its exclusively bamboo-feeding habits until the mid-Holocene. Our findings provide evidence of a historical directional niche change along which the panda has currently reached the lower limits of temperature and precipitation conditions existing on the geography where its food is available. Our proposed ENM based on the panda’s food habits accurately predicted 85.7% of the LGM fossils, in stark contrast with the traditional approach of modeling the distribution of species by using exclusively its own occurrences. These results provide insights on how to include Eltonian components to undertake more robust ENM when only abiotic variables are available. We emphasize the importance of integrating fossil information, whenever available, into the niche modeling process to include the historical component when estimating species ecological niches.

中文翻译：

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大熊猫、化石和竹林：末次盛冰期大熊猫（Ailuropoda melanoleuca）生态位模型

大熊猫 (Ailuropoda melanoleuca) 是熊科系统发育中最基础的生物，其特殊饮食由多种竹子组成。大熊猫的进化历史和过去的分布模式仍然知之甚少。我们的目标是综合应用不同的方法来评估大熊猫的进化历史和分布模式；这些包括系统地理学、生态位模型（ENM）和化石数据。为此，我们描述了熊猫过去和现在的生态位以及定义它们的环境条件。为了估计熊猫在其历史地理范围内的系统地理模式和环境条件（降水和温度），我们评估了它在末次盛冰期 (LGM) 期间的过去分布。考虑到模拟生物相互作用（例如觅食、捕食）仍然是一个巨大的挑战，我们提出了一种基于熊猫特殊饮食的新建模策略，使用分布在熊猫历史地理范围内的三个竹属的集合。最后，我们通过评估其预测 LGM 化石的能力来测试我们方法的准确性。我们的结果支持熊猫在其分布中的多样化发生在 ca。270万年（Mya），恰逢熊猫从肉食性转变为素食性的可能时期（从更新世到上新世），直到全新世中期才获得其完全以竹子为食的习惯。我们的研究结果提供了历史方向生态位变化的证据，大熊猫目前已达到其食物可用地理上存在的温度和降水条件的下限。我们提出的基于熊猫饮食习惯的 ENM 准确预测了 85.7% 的 LGM 化石，这与仅使用其自身出现来模拟物种分布的传统方法形成鲜明对比。这些结果提供了关于如何在只有非生物变量可用时包含 Eltonian 组件以进行更强大的 ENM 的见解。我们强调将化石信息整合到生态位建模过程中的重要性，以在估计物种生态位时包括历史成分。