Quasi-experimental determination of a mass standard in the forest millipede <em>Centrobolus inscriptus</em>

Abstract

Sexual size dimorphism (SSD) in the diplopod species Centrobolus inscriptus has a positive correlation with body size. Intraspecific intersexual variation in mass was calculated twice in this species (males: 2.48 ± 0.57g; 2.00 ± 0.22g; females: 2.27 ± 0.28g; 2.61 ± 0.42g) and data sets tested for SSD. Males differed significantly from females in body mass (students t-test: t=9.38, d.f.=95, p<0.05). This was again found in the larger sample where males and females differed significantly from each other in mass (Wilcoxon matched pairs test: T= 554, n = 88, P = 0.00). When the two data sets were pooled and the mean’s compared, a difference was found (t=2.3162, n=273; p=0.020918). It was found males were lighter and have higher reproductive success through female preference for larger males when there was Size assortative mating behaviour. Conformity to the mass standard in sexual selection was suggested. Millipedes may influence concentrations of soil elements through sex‐specific difference.