Tremayne Michelle A, Richards A J
1 Department of Agricultural and Environmental Science, Ridley Building, University of Newcastle, Newcastle NE1 7RU, UK.
New Phytol. 2000 Oct;148(1):127-142. doi: 10.1046/j.1469-8137.2000.00738.x.
Using the outcrossing Primula farinosa and its autogamous selfing relatives P. scotica, P. scandinavica and P. stricta, we compared the fitness of light and heavy seeds. Heavy seeds germinated in greater numbers and more quickly. In competition with seedlings grown from lighter seeds, heavy seeds produced larger rosettes. In P. farinosa such seedlings went on to produce more seeds, and in two populations heavier seeds, than plants from lighter seeds. After transplantation to natural populations, seedlings of P. farinosa derived from heavy seeds produced larger rosettes, more flowers and seeds than those from lighter seeds in certain populations so that seedlings born of heavy seeds were much fitter than seedlings from lighter seeds. Average seed weight varied in inverse proportion to seed number per capsule. The autogamous species produced on average about twice as many seeds per capsule as P. farinosa. In P. scotica and P. stricta this difference appears to be due in part to assured fertilization, but this high fecundity did not cause disadvantageously light seeds. As these species produced fewer capsules per scape, their overall seed production was on average no greater than for P. farinosa. P. farinosa traded-off fitness between capsules with large seed numbers, which donated more offspring to the next generation, and those with small seed numbers, whose heavy seeds would be more likely to reproduce themselves in the next generation. We conclude that low fecundity in outcrossing species might at times be advantageous.
通过使用异交的粉报春及其自花授粉的近缘种苏格兰报春、斯堪的纳维亚报春和狭叶报春，我们比较了轻重不同种子的适合度。较重的种子发芽数量更多且更快。在与由较轻种子长成的幼苗竞争时，较重的种子长出的莲座叶更大。在粉报春中，这样的幼苗比由较轻种子长成的植株能结出更多种子，并且在两个种群中，较重种子长成的植株也是如此。移植到自然种群后，在某些种群中，由较重种子发育而来的粉报春幼苗比由较轻种子发育而来的幼苗长出的莲座叶更大、花朵和种子更多，因此由较重种子产生的幼苗比由较轻种子产生的幼苗更具适合度。平均种子重量与每个蒴果中的种子数量成反比。自花授粉物种每个蒴果平均产生的种子数量约为粉报春的两倍。在苏格兰报春和狭叶报春中，这种差异似乎部分归因于确保受精，但这种高繁殖力并没有导致种子过轻带来不利影响。由于这些物种每个花葶产生的蒴果较少，它们的总体种子产量平均并不高于粉报春。粉报春在具有大量种子的蒴果（为下一代贡献更多后代）和具有少量种子的蒴果（其较重的种子更有可能在下一代中自我繁殖）之间进行了适合度的权衡。我们得出结论，异交物种的低繁殖力有时可能是有利的。
