van Dijk Th S
Biological Station of the Agricultural University, Kampsweg 27, NL-Wijster (Drenthe), The Netherlands.
Oecologia. 1979 Jan;40(1):63-80. doi: 10.1007/BF00388811.
In this study the inverse relationship between the amount of reproduction in female carabid beetles and their survival until the next breeding season, suggested by Murdoch (1966), was examined in Pterostichus coerulescens L. and Calathus melanocephalus L. This was tested with individual and differently reproducing females, kept at the same temperature, as well as with groups of females kept at different temperatures, i.e. with very different overall levels of reproduction.No relationship was found between the numbers of eggs laid by individual females and their survival until the next breeding season.The numbers of eggs laid by individual females varies greatly, even under constant and optimal conditions,. In contrast to this, an individual female continues to lay a characteristic number of eggs over several succeeding weeks. The amount of reproduction is highly correlated with temperature when food is optimal. In P. coerulescens there was a positive correlation between the amount of reproduction of the same individuals in two succeeding years, whereas in C. melanocephalus no relationship could be found.Both in the field and in our experiments individuals of P. coerulescens generally live for 3 to 4 years, longer than C. melanocephalus which usually only lives for 2 years. The 3-4 year-old individuals of P. coerulescens die during the breeding season or shortly afterwards, but also during the winter, whereas the 2-3 year-old individuals of C. melanocephalus die during the winter. Males and females show a similar mortality after breeding. The level of reproduction of a population depends on the proportion of old beetles, since especially the very old ones die before the end of the breeding season.We reject the hypothesis of Murdoch because of these data. However, in a different way from that of Murdoch, we also suggest that old beetles are of great importance for the survival of a population, namely that this form of heterogeneity of a population may enhance its stability under varying environmental conditions.
在本研究中，对默多克（1966年）提出的雌性步甲繁殖量与其存活至下一个繁殖季节之间的反比关系，在青步甲和黑头婪步甲中进行了检验。这一关系通过在相同温度下饲养的个体繁殖情况不同的雌性步甲，以及在不同温度下饲养的雌性步甲群体（即繁殖总体水平差异很大的群体）进行了测试。未发现个体雌性步甲产卵数量与其存活至下一个繁殖季节之间存在关联。即使在恒定且最佳的条件下，个体雌性步甲产卵数量也差异极大。与此相反，单个雌性步甲在连续数周内会持续产下特定数量的卵。当食物充足时，繁殖量与温度高度相关。在青步甲中，同一批个体在连续两年中的繁殖量呈正相关，而在黑头婪步甲中未发现这种关系。在野外和我们的实验中，青步甲个体一般能存活3至4年，比通常仅存活2年的黑头婪步甲寿命长。3至4岁的青步甲个体在繁殖季节或之后不久死亡，但也会在冬季死亡，而2至3岁的黑头婪步甲个体在冬季死亡。繁殖后，雄性和雌性的死亡率相似。种群的繁殖水平取决于老龄甲虫的比例，因为特别是非常老龄的甲虫会在繁殖季节结束前死亡。基于这些数据，我们否定了默多克的假设。然而，与默多克不同的是，我们还认为老龄甲虫对种群的生存至关重要，即种群的这种异质性形式可能会增强其在不同环境条件下的稳定性。
