Sexual vs. asexual reproduction in a stick insect (Megaphasma dentricus)

The paradox of sex is one of biology’s great evolutionary enigmas, particularly in those taxa that are fully capable of both sexual and asexual reproduction.  To quantify how fitness varies between these two modes of reproduction, we explored lifetime fecundity in Megaphasma dentricus, the giant walking stick of North America.  For the first 20 days of egg laying, there were no fecundity differences between sexual and asexual females with respect to egg number or egg weight; all females laid a total of ~50 eggs and each egg weighed about .02g.  For days 21-50 (the last 30 days of egg laying), asexually reproducing females laid significantly fewer (but not lighter) eggs than sexual females.  Overall, lifetime fecundity in asexually reproducing females was about 5-10% less than sexually reproducing females.  Myriad factors remain unexplored in this species, including the ploidy of sexually and asexually produced eggs, the effect of parasites or other considerations of co-evolution (e.g., the Red Queen Hypothesis), and the accumulation of deleterious mutations (e.g., Muller’s Ratchet).