Why Sexual Size Dimorphism Increases with Longitude, Precipitation and Temperature and Decreases with Latitude in Forest Millipedes Centrobolus Cook, 1897

The objectives of this study were to determine what happened when Bergmann’s Rule meets Rensch’s Rule Sexual Size Dimorphism (SSD) and body size changed with eco-geographical factors. Latitude, longitude, precipitation and temperature were correlated with body size and SSD in the forest millipede genus Centrobolus. There were significant positive correlations between SSD and longitude (r=0.37, Z score=1.71, n=22, p=0.04), precipitation (r=0.29, Z score=1.28, n=22, p<0.10) and temperature (r=0.34, Z score=1.49, n=22, p<0.07). There was a significant correlation between SSD and latitude (r=-0.44, Z score=2.05, n=22, p=0.02). Eco-geographical variance in the polygynandrous reproductive systems occur with larger females and higher SSD occurring in warmer, wetter north-eastern habitats.