Abstract
Mating between closely related individuals is often associated with fitness declines. However, less is known about consequences of inbreeding for (sexual) chemical signaling traits and for mate choice and acceptance. Thus, we investigated effects of inbreeding on the chemical phenotype, i.e., the profile and diversity of putative cuticular hydrocarbons (CHCs) in the leaf beetle Phaedon cochleariae Fabricius. Moreover, we tested mating probabilities in no choice bioassays with different combinations of outbred and inbred beetles. Finally, we tested male preferences and female aggression in a dual choice bioassay with one outbred male, one outbred and one inbred female. The chemical phenotype was altered in inbred females, which showed a male-like CHC profile. In no choice bioassays, inbred individuals had a decreased mating probability than outbred individuals. Changes in the chemical phenotype of inbred females might be involved in the negative inbreeding effects on mating acceptance. When having the choice, males did not show any preference between outbred and inbred females. However, inbred females were more aggressive in these situations, potentially to raise their chances to be mated, because due to inbreeding depression they have lower reproductive perspectives than outbred females. Overall, inbreeding effects on the chemical phenotype, mating acceptance and female aggression might have consequences for the population dynamics and development of the individuals. In conclusion, these results suggest that inbreeding events have the potential to affect sexual selection of chemical signaling traits and evolutionary processes underlying mating strategies.
Highlights
The mating between close relatives, i.e., inbreeding, is often associated with a loss of individual fitness in inbred compared to outbred offspring, called inbreeding depression (Charlesworth and Charlesworth, 1987)
The chemical phenotype, i.e., the cuticular hydrocarbons (CHCs) profile, of adult beetles was significantly affected by the sex of the individuals and the interaction of the breeding status and the sex (Table 2)
The present study disclosed that the chemical phenotype, mating probability and female aggression are affected by inbreeding in P. cochleariae
Summary
The mating between close relatives, i.e., inbreeding, is often associated with a loss of individual fitness in inbred compared to outbred offspring, called inbreeding depression (Charlesworth and Charlesworth, 1987). Examples range from inbreeding impacts on chemical (Thom et al, 2008; van Bergen et al, 2013; Menzel et al, 2016) to acoustic traits (Aspi, 2000; Drayton et al, 2007, 2010). Cuticular hydrocarbons (CHCs), cuticular lipids and sex pheromones trigger mating behavior and preferences (Howard and Blomquist, 2005; Lihoreau and Rivault, 2009; van Bergen et al, 2013; Keppner et al, 2017). The sex pheromone amount of male Bicyclus anynana butterflies is lower in inbred than in outbred individuals, which reduces the mating success of inbred males (van Bergen et al, 2013). Inbreeding decreases the CHC diversity of the ant Hypoponera opacior, which potentially leads to an adjustment of reproduction strategies in this species (Menzel et al, 2016)
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