Ebert Dieter
Institut of Zoology, University of Basel, Rheinsprung 9, CH-4051, Basel, Switzerland.
Oecologia. 1991 Apr;86(2):243-250. doi: 10.1007/BF00317537.
Life-history traits of 101 clones from two populations of Daphnia magna were measured under controlled environmental conditions in the laboratory. Some individuals had four juvenile instars, others had five. This depended on their length at birth and on the population they came from. Females in the group with five juvenile instars were smaller at birth but larger and older at maturity than those with four juvenile instars. Within groups of females with equal numbers of preadult instars (instar groups) age and size at maturity increased with size at birth. This relationship differed significantly among instar groups for both age and size at maturity. Significant differences in age and size at maturity between two populations became non-significant when size at birth was used as a covariable in AN-COVA. Within populations, size at birth depended on the clone and on the parity of the clutch. First-clutch offspring were considerably smaller than those from later clutches. The results suggest that variability in life-history traits is common within and between clones, but that most of this variation can be accounted for by size at birth and the number of pre-adult instars.
在实验室可控环境条件下，对来自大型溞两个种群的101个克隆体的生活史特征进行了测量。一些个体有4个幼龄期，另一些有5个。这取决于它们出生时的体长以及它们所来自的种群。有5个幼龄期的组中的雌性出生时较小，但成熟时比有4个幼龄期的雌性更大且更年长。在具有相等数量成年前龄期的雌性组（龄期组）中，成熟时的年龄和大小随出生时的大小增加。对于成熟时的年龄和大小，这种关系在龄期组之间存在显著差异。当在协方差分析（AN-COVA）中将出生时的大小用作协变量时，两个种群之间成熟时年龄和大小的显著差异变得不显著。在种群内部，出生时的大小取决于克隆体和卵块的胎次。第一胎后代比后来胎次的后代小得多。结果表明，生活史特征的变异性在克隆体内部和之间都很常见，但这种变异的大部分可以由出生时的大小和成年前龄期的数量来解释。
