Trigoniulid size dimorphism breaks Rensch

Abstract

This present research aims to clarify the relative sexual size dimorphism of Centrobolus (Cook) in 18 congenerics. Millipedes illustrated reversed sexual size dimorphism (SSD) where females were larger than males; and break Rensch’s rule as this dimorphism increased with body size. SSD was calculated in 18 species of the genus Centrobolus and illustrated was illustrated in 2 regressions: (1) male versus female SSD and (2) SSD and body size. The allometric equation for Centrobolus was (1) ŷ=0.00051X0.01071. SSD ranged from 0.63–2.89 (1.55±0.63; n≥18) and was not negatively correlated (R=0.70485; P=0.00109; n=18 spp.) with a volumetric index of body size ranging from 284–2683 mm3 (1097.89±638.06; 18). The rejection of the rule appears consistent in some animals.