Real Jardín Botánico, CSIC, Plaza de Murillo 2, ES-28014, Madrid, Spain.
Department of Molecular Biology and Biochemical Engineering, Universidad Pablo de Olavide, Carretera de Utrera km 1, ES-41013, Seville, Spain.
Am J Bot. 2017 Nov;104(11):1765-1774. doi: 10.3732/ajb.1700171.
Bipolar species represent the greatest biogeographical disjunction on Earth, raising many questions about the colonization and adaptive processes behind such striking distribution. We investigated climatic niche differences of five Carex bipolar species in North and South America to assess niche shifts between these two regions. Moreover, we assessed potential distribution changes with future climate change.
We used 1202 presence data points from herbarium specimens and 19 bioclimatic variables to assess climatic niche differences and potential distributions among the five species using ordination methods and Maxent.
The niche overlap analyses showed low levels of niche filling and high climatic niche expansion between North and South America. Carex macloviana and C. maritima showed the greatest niche expansion (60% and 96%, respectively), followed by C. magellanica (45%) and C. microglochin (39%). Only C. canescens did not colonize new environments (niche expansion = 0.2%). In contrast, all species but C. magellanica had niche filling that was <40%; hence, they are absent in the south from many environments they inhabit in North America. Climate change will push all species toward higher latitudes and elevation, reducing the availability of suitable environments.
The colonization of South America seems to have involved frequent climatic niche shifts. Most species have colonized new environments from those occupied in the North. Observed niche shifts appear congruent with time since colonization and with current genetic structure within species. In these cold-dwelling species, climate change will most likely decrease their suitable environments in the future.
双极种代表了地球上最大的生物地理分离，这引发了许多关于这种惊人分布背后的殖民和适应过程的问题。我们调查了北美和南美的五种 Carex 双极种的气候生态位差异，以评估这两个地区之间的生态位转移。此外，我们评估了未来气候变化下的潜在分布变化。
我们使用了来自植物标本的 1202 个存在数据点和 19 个生物气候变量，使用排序方法和最大熵法评估了这五个物种之间的气候生态位差异和潜在分布。
生态位重叠分析表明，北美和南美之间的生态位填充水平较低，气候生态位扩张较高。Carex macloviana 和 C. maritima 表现出最大的生态位扩张（分别为 60%和 96%），其次是 C. magellanica（45%）和 C. microglochin（39%）。只有 C. canescens 没有殖民新环境（生态位扩张=0.2%）。相比之下，除了 C. magellanica 之外，所有物种的生态位填充都<40%；因此，它们在南方有许多在北美栖息的环境中没有出现。气候变化将迫使所有物种向更高的纬度和海拔推进，减少适宜环境的可用性。
南美似乎经历了频繁的气候生态位转移。大多数物种从北方占据的环境中殖民到新的环境。观察到的生态位转移与殖民时间和物种内当前的遗传结构一致。在这些寒冷居住的物种中，气候变化很可能在未来减少它们适宜的环境。
