Blanckenhorn W U
Zoologisches Museum der Universität Zürich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland fax: +(41) 1-364-0295; e-mail:
Oecologia. 1997 Feb;109(3):342-352. doi: 10.1007/s004420050092.
Field phenologies of high- (ca. 1500 m) and low- (ca. 500 m) altitude populations of the two most common European species of dung flies, Scathophaga stercoraria and Sepsis cynipsea, differ quite markedly due to differences in climate. To differentiate genetic adaptation due to natural selection and phenotypic plasticity, I compared standard life history characters of pairs of high- and low-altitude populations from three disjunctive sites in Switzerland in a laboratory experiment. The F1 rearing environment did not affect any of the variables of the F2 generation with which all experiments were conducted; hence, there were no carry-over or maternal effects. In Sc. stercoraria, high-altitude individuals were smaller but laid larger eggs; the latter may be advantageous in the more extreme (i.e. more variable and less predictable) high-altitude climate. Higher rearing temperature strongly decreased development time, body size and the size difference between males and females (males are larger), produced female-biased sex ratios and led to suboptimal adult emergence rates. Several of these variables also varied among the three sites, producing some interactions complicating the patterns. In Se. cynipsea, high-altitude females were marginally smaller, less long-lived and laid fewer clutches. Higher rearing temperature strongly decreased development time and body size but tended to increase the size difference between males and females (males are smaller); it also increased clutch size but decreased physiological longevity. Again, interpretation is complicated by variation across sites and some significant interactions. Overall, genetic adaptation to high-altitude conditions appears weak, probably prevented by substantial gene flow, and may be swamped by the effects of other geographic variables among populations. In contrast, phenotypic plasticity is extensive. This may be due to selection of flexible, multi-purpose genotypes. The results suggest that differences in season length between high- and low-altitude locations alone do not explain well the patterns of variation in phenology and body size.
欧洲两种最常见的粪蝇，即腐蝇和黄腹蝇，其高海拔（约1500米）和低海拔（约500米）种群的野外物候由于气候差异而有相当明显的不同。为了区分自然选择导致的遗传适应和表型可塑性，我在一项实验室实验中比较了来自瑞士三个不连续地点的高海拔和低海拔种群对的标准生活史特征。F1代的饲养环境对所有实验所涉及的F2代的任何变量都没有影响；因此，不存在遗留效应或母体效应。在腐蝇中，高海拔个体较小，但产下的卵较大；在更为极端（即更多变且更不可预测）的高海拔气候中，后者可能具有优势。较高的饲养温度会强烈缩短发育时间、减小体型以及减小雌雄个体之间的体型差异（雄性体型较大），产生偏雌性的性别比例，并导致成虫羽化率不理想。这些变量中的几个在三个地点之间也有所不同，产生了一些相互作用，使模式变得复杂。在黄腹蝇中，高海拔雌性个体略小，寿命较短，产卵次数较少。较高的饲养温度会强烈缩短发育时间和减小体型，但往往会增加雌雄个体之间的体型差异（雄性体型较小）；它还会增加产卵量，但会降低生理寿命。同样，由于地点间的差异和一些显著的相互作用，解释变得复杂。总体而言，对高海拔条件的遗传适应似乎很弱，可能是由于大量基因流的阻碍，并且可能被种群间其他地理变量的影响所掩盖。相比之下，表型可塑性很广泛。这可能是由于选择了灵活的、多功能的基因型。结果表明，仅高海拔和低海拔地点之间季节长度的差异并不能很好地解释物候和体型变化的模式。
