随着年龄的增长,生殖能力的下降在整个生命之树中很常见。然而,在植物中,交配系统特征很少被测试衰老的迹象。由于繁殖通常是资源有限的,我们可能会期望异类和自类类群以不同的方式分配这些资源,尤其是随着植物年龄的增长。与自拍者相比,外向者预计会产生艳丽的,奖励吸引传粉者的花朵和可以成功竞争胚珠的高质量花粉。然而,这种资源密集型的外向型策略可能会导致花卉分配和花粉性能指标的下降,相对于自拍。
为了探索与年龄相关的生殖变化,我们测量了一个年度姐妹物种对的多个种群在开花期的花大小和花粉发芽能力,直线混血儿(outcrosser)和C.rattanii(selfer),在生长室实验中。
我们发现两个物种的花大小都随着年龄的增长而显著下降。随着年龄的增长,花粉发芽能力显着下降(88%)。而自鼠花粉萌发性下降不显著且较低(17%)。
我们的结果支持这样的观点,即与自交者相比,外交者更高的再生产总成本可以更快地耗尽可用资源,表现为雄性表现随植物年龄的下降。
Declines in reproductive capabilities with increasing age are common across the tree of life. However, in plants, mating system traits have rarely been tested for signs of senescence. Since reproduction is often resource limited, we might expect outcrossing and selfing taxa to allocate these resources differently, especially as a plant ages. Compared with selfers, outcrossers are expected to produce showy, rewarding flowers that attract pollinators and high-quality pollen that can successfully compete for ovules. Yet, this resource-intensive strategy of outcrossers may result in declines in floral allocation and pollen performance metrics, relative to selfers.
To explore age-related changes in reproduction, we measured flower size and pollen germinability over the flowering period for multiple populations of an annual sister species pair, Collinsia linearis (outcrosser) and C. rattanii (selfer), in a growth chamber experiment.
We found that flower size decreased significantly with age in both species. The outcrosser expressed a significant and dramatic (88%) decline in pollen germinability with age, while the selfer\'s pollen germinability decline was non-significant and low (17%).
Our results support the idea that the higher total cost of reproduction in outcrossers can deplete available resources more rapidly than in selfers, manifesting as a decline in male performance with plant age.