Copulation and sexual size dimorphism in worm-like millipedes

Abstract

The prediction that copulation duration is shorter when sexual size dimorphism increases was tested in juliform millipedes at the population-level and species-level by tabulating and correlating ratios for mean sexual size dimorphism ranging from 1.0-1.6 (n=310) with mean copulation duration ranging from 34-206 minutes (n=391) in 8 taxa: ord. Spirostreptida fam. Odontopygidae gen. Odontopyge (n=2spp.), Spinotarsus (n=1sp.) and fam. Spirostreptidae gen. Calostreptus (n=1sp.), Doratogonus (n=1sp.); and ord. Spirobolida fam. Trigoniulidae gen. Centrobolus (n=3spp.). Copulation duration and sexual size dimorphism were inversely correlated across populations (r=-0.5975, N=11, P=0.05) but not species. This study contributes to the allometry of copulation.