Chirally dimorphic male genitalia in praying mantids (Ciulfina: Liturgusidae)

Abstract

Although male polymorphisms occur widely in nature and have received considerable recent attention from studies of alternative mating strategies, male genital polymorphisms are less well known. Here, we describe a dimorphism in the orientation of the male genitalic complex of the praying mantid genus Ciulfina. Populations of Ciulfina species vary in the proportion of males with dextral (right-oriented) and sinistral (left-oriented) genitalia, ranging from directional asymmetry (single orientation only) to apparent antisymmetry (equal proportions of both orientations). The proportion of dextral males varied between species (C. baldersoni: 46%; C. rentzi: 24%; C. klassi: 100%; C. biseriata: 83%) and between populations. We used elliptic Fourier analysis to quantify shape and size variation between the genitalia of dextral and sinistral males and determined that the two forms were mirror images of one another in two species. We found that the level of mechanical reproductive isolation between heterospecific populations of opposite genital orientation was no greater than that between heterospecific populations with the same orientation or of mixed orientation. Genital orientation therefore did not influence premating isolation between these species, despite complete postmating isolation. The geographic proximity of populations to heterospecifics also showed no particular pattern with respect to genital orientation. These results suggest that reversible trait asymmetry in Ciulfina is not driven by reproductive isolation, and add to the growing evidence against the species isolation hypothesis for rapid genital evolution.