Data from: Conflicting selection on the timing of germination in a natural population of Arabidopsis thaliana

The timing of germination is a key life-history trait that may strongly influence plant fitness and that sets the stage for selection on traits expressed later in the life cycle. In seasonal environments, the period favourable for germination and the total length of the growing season are limited. The optimal timing of germination may therefore be governed by conflicting selection through survival and fecundity. We conducted a field experiment to examine the effects of timing of germination on survival, fecundity and overall fitness in a natural population of the annual herb Arabidopsis thaliana in north-central Sweden. Seedlings were transplanted at three different times in late summer and in autumn covering the period of seed germination in the study population. Early germination was associated with low seedling survival, but also with high survival and fecundity among established plants. The advantages of germinating early more than balanced the disadvantage and selection favoured early germination. The results suggest that low survival among early germinating seeds is the main force opposing the evolution of earlier germination and that the optimal timing of germination should vary in space and time as a function of the direction and strength of selection acting during different life-history stages.

种子萌发时机是一项核心生活史性状，可强烈影响植物适合度，并为后续生活周期中表达的性状的选择奠定了基础。在季节性环境中，适宜萌发的时段与生长季总时长均较为有限。因此，最优萌发时机可能受到存活与繁殖力两方面相互拮抗的选择压力的调控。我们以瑞典中北部一年生草本植物拟南芥（Arabidopsis thaliana）的自然种群为研究对象，开展了一项野外实验，旨在探究萌发时机对植株存活、繁殖力及整体适合度的影响。该研究种群的种子萌发期覆盖夏末至秋季，我们在此期间设置了三个移栽节点，对幼苗进行定植。早萌发的幼苗存活率较低，但定植后的植株却拥有更高的存活率与繁殖力。早萌发带来的优势远超其劣势，因此自然选择更青睐早萌发的策略。研究结果显示，早萌发种子的低存活率是阻碍更早萌发策略演化的核心阻力，且最优萌发时机应随空间与时间动态变化，其变化规律取决于不同生活史阶段所经受的选择压力的方向与强度。