Genetic variation of relative growth rates in Notonecta undulata: I. The relation of femur length to body length

Abstract

This paper presents the first part of a further analysis of data collected many years ago by Clark and Hersh on allometric growth in Notonecta undulata, the water boatman. The data consist of measurements of a number of dimensions, taken each instar, on 72 individuals reared separately from egg to adult. These individuals were the progeny of nine wild females, so that a rough estimate can be made of the magnitude of genetic effects by comparing the variances within and between families. The paper examines the allometric relationship between femur length of the three legs and body length.The statistical problems in this type of analysis are discussed. There are significant deviations from linearity when the six points for femur length are plotted against body length on a double log graph, but these are small compared with the overall linear trend. The growth coefficients (k) are calculated for the three femurs against body length for each individual, and are analysed for differences between femurs, between sexes and between and within families. This analysis shows that there are significant differences between the three femurs in growth coefficient, but the growth gradient, or pattern of k values between the three femurs does not vary significantly from one individual to another. On the other hand, mean k for the three femurs shows significant individual variation and also a significant variation between families. From this it appears that about one third of the phenotypic variance in mean relative growth rate of the femurs is due to genetic effects.