Latitudinal-size trend in eight species of Centrobolus

Abstract

Bergmann's eco-geographical rule maintained within a taxonomic clade, populations and species of larger size were found in colder environments, and species of smaller size were found in warmer regions. It was tested in the millipede genus Centrobolus with reversed sexual size dimorphism (SSD). Two factors were measured from eight Centrobolus species, body lengths (mm) and widths (mm). Centrobolus male lengths were positively related to latitude (r=0.643, r2=0.4134, n=8, p=0.085467). The short species, C. digrammus occurred at the southern tips of South Africa (-34.19°S) while longer species, C. inscriptus and C. anulatus were found north (-28.98°S). In-between these two latitudes all the medium sized species ranged.