Krebs R A, Loeschcke V
Department of Biological, Geological and Environmental Sciences, Cleveland State University, 2399 Euclid Ave., Cleveland, Ohio 44115, USA.
Heredity (Edinb). 1999 Jul;83 ( Pt 1):46-53. doi: 10.1038/sj.hdy.6885410.
Although exposure to environmental stress is common in most populations, and the physiological effects of stress on individuals are well studied, the evolutionary importance of stress to populations is not well understood. To address multitrait responses to environmental change and potential constraints on character evolution, we analysed, in 100 isofemale lines of Drosophila buzzatii, the genetic relationships between resistance to a short heat shock and several life-history traits: survival in benign conditions, larval developmental time, fecundity and longevity. Estimates of heritability of larval thermotolerance were low, but significant, and all life-history traits varied significantly among isofemale lines. Several of these traits covaried significantly. Most correlations indicated positive life-history relationships, but males and females from lines where female fecundity was higher developed more slowly in the absence of stress, which is a negative life-history relationship. The stress reduced or negated many trait associations, and showed one additional relationship; more larvae from lines that developed fast at 25 degrees C survived to adult after stress than did larvae from slow developing lines. These shifts in fitness relationships, when a single stress bout is applied, suggest that even small increases in environmental stress can have profound effects on evolutionary relationships among life-history traits.
尽管在大多数种群中，暴露于环境压力是常见现象，并且压力对个体的生理影响已得到充分研究，但压力对种群进化的重要性却尚未得到很好的理解。为了探讨对环境变化的多性状反应以及性状进化的潜在限制，我们在100个巴氏果蝇同雌系中分析了对短期热休克的抗性与几个生活史性状之间的遗传关系：在良性条件下的存活率、幼虫发育时间、繁殖力和寿命。幼虫耐热性的遗传力估计值较低，但具有显著性，并且所有生活史性状在同雌系之间存在显著差异。其中几个性状显著协变。大多数相关性表明生活史之间呈正相关，但在无压力条件下，雌性繁殖力较高的品系中的雄性和雌性发育较慢，这是一种负生活史关系。压力减少或消除了许多性状关联，并显示出另一种关系；在25摄氏度下发育快的品系中的幼虫比发育慢的品系中的幼虫在压力后存活至成虫的数量更多。当施加单次压力时，这些适合度关系的变化表明，即使环境压力的小幅增加也可能对生活史性状之间的进化关系产生深远影响。
