Rauser Casandra L, Abdel-Aal Yasmine, Shieh Jonathan A, Suen Christine W, Mueller Laurence D, Rose Michael R
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697-2525, USA.
Exp Gerontol. 2005 Aug-Sep;40(8-9):660-70. doi: 10.1016/j.exger.2005.06.006.
Previous studies have demonstrated that fecundity, like mortality, plateaus at late ages in cohorts of Drosophila melanogaster. Although evolutionary theory can explain the decline and plateau in cohort fecundity at late ages, it is conceivable that lifelong heterogeneity in individual female fecundity is producing these plateaus. For example, consistently more fecund females may die at earlier ages, leaving only females that always laid a low number of eggs preponderant at later ages. We simulated fecundity within a cohort, assuming the two phenotypes described above, and tested these predictions by measuring age of death and age-specific fecundity for individual females from three large cohorts. We statistically tested whether there was enough lifelong heterogeneity in fecundity to produce a late-life plateau by testing whether early female fecundity could predict whether that female would live to lay eggs after the onset of the population fecundity plateau. Our results indicate that heterogeneity in fecundity is not lifelong and thus not likely to cause late-life fecundity plateaus. Because lifelong heterogeneity models for fecundity are based on the same underlying assumptions as heterogeneity models for late-life mortality rates, our test of this hypothesis is also an experimental test of lifelong heterogeneity models of late life generally.
先前的研究表明，与死亡率一样，黑腹果蝇群体的繁殖力在晚年时趋于平稳。尽管进化理论可以解释群体繁殖力在晚年的下降和平稳现象，但可以想象，个体雌性繁殖力的终身异质性导致了这些平稳现象。例如，繁殖力始终较高的雌性可能在较早年龄死亡，导致在晚年时仅剩下产卵量一直较低的雌性占主导地位。我们假设上述两种表型，模拟了群体内的繁殖力，并通过测量来自三个大群体的个体雌性的死亡年龄和特定年龄繁殖力来检验这些预测。我们通过测试早期雌性繁殖力是否能够预测该雌性在群体繁殖力平稳期开始后是否能存活产卵，从统计学上检验了繁殖力是否存在足够的终身异质性以产生晚年平稳期。我们的结果表明，繁殖力的异质性并非终身存在，因此不太可能导致晚年繁殖力平稳期。由于繁殖力的终身异质性模型与晚年死亡率的异质性模型基于相同的基本假设，我们对这一假设的检验也是对晚年一般终身异质性模型的实验检验。
