Carcass Scavenging Relaxes Chemical-Driven Female Interference Competition

Abstract

24Female-female nonsexual interference competition is rapidly emerging as a major fitness 25 determinant of biased sex-ratio groups with high female density. How do females overcome such 26 competition? We used adult flour beetle Tribolium castaneum to answer this question, where 27 females from female-biased groups suppressed each other's fecundity by secreting toxic quinones 28 from their stink glands, revealing a chemical-driven interference competition. The added natal 29 resource did not alleviate these fitness costs. Females also did not disperse more at high female-30 density. Hence, the competition was neither limited by the total resource availability nor the 31 inability to avoid chemical interference. Instead, protein sequestered via scavenging of nutrient-32 rich carcasses relaxed the female competition, by increasing their fecundity and reducing the 33 quinone content. Even infected carcasses were scavenged to extract fitness benefits, despite the 34 infection-risk. Finally, individual stink gland components triggered carcass-scavenging to increase 35 fecundity, indicating a potentially novel chemical feedback loop to reduce the competition. 36 37 38 39 40 41 42 43 44 45 46 3