Patterns of gene flow across elevation in Andean scarabs

Janzen's seasonality hypothesis predicts that organisms inhabiting environments with limited climatic variability will evolve a reduced thermal tolerance breadth compared with organisms experiencing greater climatic variability. In turn, narrow tolerance breadth may select against dispersal across strong temperature gradients, such as those found across elevation. This can result in narrow elevational ranges and generate a pattern of isolation-by-environment, or neutral genetic differentiation correlated with environmental variables that is independent of geographic distance. We generated genome-wide SNP data from 5 species of dung beetle from the two elevational transects and two horizontal control transects in the Ecuadorean Andes to test this prediction.

詹森季节性假说（Janzen's seasonality hypothesis）预测：相较于栖息于气候变异性更高环境中的生物，生活在气候变异性受限环境中的生物，其演化出的热耐受宽度会更窄。反之，较窄的耐受宽度可能会阻碍生物跨越强温度梯度（如沿海拔梯度形成的温度梯度）进行扩散。这一过程可能导致物种形成狭窄的海拔分布范围，并产生环境隔离（isolation-by-environment）模式，即中性遗传分化与环境变量相关，且独立于地理距离。为验证该假说预测，我们从厄瓜多尔安第斯山脉的两条海拔样带与两条水平对照样带的5种蜣螂中获取了全基因组单核苷酸多态性（Single Nucleotide Polymorphism，SNP）数据。