Leguminosae endemic to the Chaco facing quaternary climate fluctuations

ABSTRACT We investigated the influence of Quaternary climate fluctuations on the current distribution of three species of Leguminosae (Fabaceae) occurring in the Chaco. Potential distribution models of Bauhinia hagenbeckii, Muellera nudiflora and Neltuma rubriflora with a supposed endemism area were generated. The Last Interglacial, Last Glacial Maximum, Holocene Middle and current scenarios were used. The species showed a potential distribution according to the South American biogeographic history regarding the glacier regression and the formation of the Dry Diagonal. The models for each Quaternary event exhibited a tolerable AUC ≥ 0.9 for the validations. The LGM was the event that favoured the current species establishment areas in the Dry Diagonal. Quaternary climatic events were related to the current Leguminosae distribution. Bauhinia hagenbeckii and Neltuma rubriflora present similar areas of environmental suitability. Muellera nudiflora models with areas of environmental suitability were larger for the LIG and Holocene than for areas from other periods. All scenario models (LGM, HM and current scenario) highlighted the potential distribution of the three species concomitant with the glacier regression events and were consistent with the history of formation of South American dry areas.

摘要：本研究探讨了第四纪气候波动对南美查科地区三种豆科（Fabaceae）植物当前分布格局的影响。研究构建了Bauhinia hagenbeckii、Muellera nudiflora及Neltuma rubriflora的潜在分布模型，其分布区被推测为特有分布区域。本研究采用了末次间冰期、末次盛冰期、中全新世及当前气候共四种气候情景。结果显示，三个物种的潜在分布格局符合南美生物地理历史特征，即冰川退缩与干旱对角带（Dry Diagonal）的形成过程。各第四纪气候事件对应的模型验证结果均表现出可接受的曲线下面积（AUC）值≥0.9。末次盛冰期是促成三个物种现今在干旱对角带建立分布区的关键气候事件。第四纪气候事件与豆科植物当前的分布格局密切相关。Bauhinia hagenbeckii与Neltuma rubriflora的适宜生境区域面积相似。Muellera nudiflora的适宜生境面积在末次间冰期和中全新世情景下较其他时期更大。所有情景模型（末次盛冰期、中全新世及当前情景）均显示三个物种的潜在分布与冰川退缩事件同步，且与南美干旱区域的形成历史一致。