Delph Lynda F, Gehring Janet L, Arntz A Michele, Levri Maureen, Frey Frank M
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Am Nat. 2005 Oct;166 Suppl 4:S31-41. doi: 10.1086/444597.
In dioecious plants, females typically invest more biomass in reproduction than males and consequently experience stronger life-history trade-offs. Sexual dimorphism in life history runs counter to this pattern in Silene latifolia: females acquire less carbon and invest more biomass in reproduction, but males pay a higher cost of reproduction. The species is sexually dimorphic for many traits, especially flower number, with males producing many, small flowers compared to females. We tested whether the cost of reproduction is higher in males because flower number, which we presume to be under sexual selection in males, is genetically correlated with traits that would affect life-history trade-offs. We performed artificial selection to reduce the sexual dimorphism in flower size and looked at correlated responses in ecophysiological traits. We found significant correlated responses in total vegetative mass, leaf mass, leaf thickness, and measures of CO(2) exchange. Individuals in the many-and-small-flowered selection lines did not grow as large or invest as much biomass in leaves, and their leaves exhibited an up-regulated physiology that shortened leaf life span. Our results are consistent with the hypothesis that genetic correlations between floral display and ecophysiological traits lead to a higher cost of reproduction for males.
在雌雄异株植物中，雌性通常比雄性在繁殖上投入更多的生物量，因此经历更强的生活史权衡。在宽叶蝇子草中，生活史的性二态性与这种模式相反：雌性获取的碳较少，在繁殖上投入更多的生物量，但雄性付出更高的繁殖代价。该物种在许多性状上存在性二态性，尤其是花的数量，与雌性相比，雄性产生许多小花。我们测试了雄性的繁殖代价是否更高，因为我们推测在雄性中受性选择影响的花的数量与会影响生活史权衡的性状存在遗传相关性。我们进行了人工选择以减少花大小的性二态性，并观察了生理生态性状的相关反应。我们在总营养体质量、叶片质量、叶片厚度和二氧化碳交换测量方面发现了显著的相关反应。多花小朵选择系中的个体生长得没有那么大，在叶片上投入的生物量也没有那么多，并且它们的叶片表现出一种上调的生理状态，缩短了叶片寿命。我们的结果与以下假设一致，即花展示与生理生态性状之间的遗传相关性导致雄性的繁殖代价更高。
