Adaptive response of reproductive characteristics of Trifolium repens on time scale

Abstract

That trade-offs result from the allocation of limited resources is a central concept of life history evolution. Many plants combine sexual reproduction with asexual reproduction, and the relationships between different reproductive modes reflect more general plant reproduction and resource allocation strategies, but how trade-offs between these reproductive modes affect fitness when plants face environmental changes, especially caused by changed growing seasons, is poorly understood. A long florescence (from late April to early November) and combined with sexual and asexual reproduction species, Trifolium repens, was selected in this study. We divided the flowering time of T. repens into three flowering phases, early (May to July), middle (July to September) and late (September to November), and compared the changes of environmental factors, pollinators, plant reproductive traits, resource allocation strategies and fitness of two reproductive modes at different phases, aiming to test how clonal plants change reproduction strategy to respond the environmental changes. Our results showed that the pollinator visitation activity was highest in early flowering phase and decreased as the season progressed. The seasonal fluctuations of environment condition and pollinators lead to significant differences in floral traits: the inflorescence size increased significantly in middle flowering phase (the flower length, flower numbers and inflorescence diameter were increased), and did not differ significantly between early and late flowering; the flower duration prolonged significantly in late flowering phase, but there was no significant difference between early and late flowering phase; inflorescence number and seed yield decreased along with the seasonal changing, i.e. bear the most at early, and the least inflorescences at late flowering phases. On the contrary, quantitative characteristics of stolon were increased as the season progressed. Correspondingly, a significant increase of resource allocated to sexual reproduction and decrease to asexual reproduction as the season progressed. These results indicate that the environmental factors in different flowering phases and corresponding variation in pollinators lead to different phenotypes, ultimately resulting in the divergence of plant reproductive traits. T. repens can adjust investment in the two reproductive modes with respect to the cost required for each new plant under different environment, and predicted to regulate overall fitness.