The emergence of North American grasslands occurred no earlier than the postglacial period. As a key species, Bouteloua gracilis has been widely studied, and authors have suggested a northward migration from Mexico towards the United States. B. gracilis is extremely vulnerable to present global climate change and distribution modeling at different times (Last Glacial Maximum-LGM, mid-Holocene, Present and Future) would be helpful to infer its past distribution and expansion and to predict its responses to future change. Precipitation of the driest month was the most informative variable in the distribution models. Mean temperature of the wettest quarter provided unique information for the future distribution. During the LGM, the most probable distribution of the species was limited to central Mexico and Chihuahua. The largest expansion of the B. gracilis distribution area was projected to be in the mid-Holocene. Climatic variables among the four climatic time periods were not statistically different. Postglacial expansion of B. gracilis from Mexico to the north was supported; since then the distribution area of the species has changed minimally. Future distribution predictions for B. gracilis suggest climate change will not be the sole factor affecting the distribution of the species.

北美草原的出现不早于冰期以后。作为一种重要物种，香根草已被广泛研究，作者建议从墨西哥向美国北迁。细芽孢杆菌易受当前全球气候变化和在不同时间的分布模型（上冰川期LGM，全新世中期，现在和未来）的影响非常脆弱，这有助于推断其过去的分布和扩展并预测其对未来变化的响应。在分配模型中，最干旱的月份降水量最多。最湿季的平均温度为将来的分布提供了独特的信息。在LGM期间，该物种最可能的分布仅限于墨西哥中部和奇瓦瓦州。B. gracilis分布区的最大扩展预计是在全新世中期。四个气候时间段之间的气候变量在统计上没有差异。冰雹后的B. gracilis从墨西哥到北部得到了支持；从那时起，该物种的分布区域变化很小。细小芽孢杆菌的未来分布预测表明，气候变化将不是影响物种分布的唯一因素。