Gustatory polymorphism mediates a new adaptive courtship strategy

Human-imposed selection can lead to adaptive changes in sensory traits. However, rapid evolution of the sensory system can interfere with other behaviors, and animals must overcome such sensory conflicts. In response to insecticide baits that contain glucose, German cockroaches evolved glucose-aversion (GA), which confers behavioral resistance against baits. During courtship, the male offers the female a nuptial gift that contains maltose, which expediates copulation. However, the female’s saliva rapidly hydrolyzes maltose into glucose, which causes GA females to dismount the courting male, which reduces mating success of GA females. Comparative analysis revealed two adaptive traits in GA males. They produce maltotriose, which is more resilient to salivary glucosidases, and they initiate copulation faster than wild-type (WT) males, before GA females interrupt their nuptial feeding and dismount the male. Recombinant lines of the two strains showed that the two emergent traits of GA males..., (a) Cockroach strains
All cockroaches were maintained on rodent diet (Purina 5001, PMI Nutrition International, St. Louis, MO) and distilled water at 27°C, ~40% RH and a 12:12 h L:D cycle. The WT colony (Orlando Normal) was collected in Florida in 1947 and has served as a standard insecticide-susceptible strain. The GA colony (T-164) was also collected in Florida in 1989 and shown to be aversive to glucose; continued artificial selection with glucose-containing toxic bait fixed the homozygous GA trait in this population (approximately 150 generations as of 2020).
As described in detail in our previous study [29] and in the electronic supplementary material, two recombinant colonies were initiated in 2013 by crossing 10 pairs of WT♂ × GA♀ and 10 pairs of GA♂ × WT♀ to homogenize the genetic backgrounds of the two strains. At the F8 generation (free bulk mating without selection), 400 cockroaches were separated into glucose-accepting and glucose-rejecting groups. These colonies were bred f...,