四川藏鼠兔头骨形态的种群分化

Population Subdivision in Skull Morphology of Ochotona thibetana in the Western Sichuan Mountains,China

种群分化是物种形成过程中具有决定意义的一步,是研究微进化过程的核心内容。为探讨地理隔离对小型兽类种群分化的影响,本文系统比较了四川西部3个隔离藏鼠兔Ochotona thibetana种群在头骨形态上的异同。结果表明在所测量的19个头骨形态指标中,岷山与邛崃山、邛崃山与凉山、岷山与凉山的藏鼠兔种群已分别在9、14及4个头骨变量上存在明显差异,颧宽、眶间宽、鼻骨长等变量是导致该3个山系藏鼠兔种群头骨形态发生分化的主要变量。由于藏鼠兔在各山系内部属一较为常见的物种,分析认为其头骨形态的种群分化可能与隔离状态下局部环境差异导致的选择压力不同有关。本研究揭示了在进行藏鼠兔等小型兽类种及种下阶元划分时,除数理统计手段引入的必要外,尚应充分考虑不同地理区域种群可能已产生的局部分化。

Population differentiation is a crucial step in the speciation process, and therefore it is the central subject in microevolution studies. To detect potential influence from geographical isolation upon population differentiation in small mammals, the skulls of Tibetan pikas （Ochotona thibetana） among three isolated populations in western Sichuan Province were systematically compared. The results indicated that among 19 variables involved, there were 9, 14 and 4 skull indices significantly different between Minshan-Qionglai, Qionglai-Liangshan, and Minshan-Liangshan. The variables, including the zygomatic breadth, least breadth between the orbits, greatest length of the nasals, oral height of the vertical ramus, were mainly responsible for this difference. The differentiation in skulls of Tibetan pikas in the three mountains was assumed to correlate with geographical barriers created by the uplift of the Qingzang Plateau. Future research should be directed toward uncovering the fitness consequence of these morphological differences in skulls.