Intralocus sexual conflict and environmental stress

Area of Science:

• Evolutionary biology
• Genetics
• Ecology

Background:

• Intralocus sexual conflict (IaSC) arises when selection at a single genetic locus favors different alleles in males and females.
• IaSC acts as a constraint on adaptation, but its impact may lessen in stressful environments.
• The genetic correlation for fitness between males and females (rMF) quantifies genome-wide IaSC.

Purpose of the Study:

• To compare IaSC under benign (29°C) and stressful (36°C) temperatures in two natural populations of the seed beetle Callosobruchus maculatus.
• To investigate how environmental stress affects the magnitude and direction of IaSC.
• To determine if environmentally sensitive alleles mediate changes in IaSC.

Main Methods:

• Estimating rMF in isofemale lines from two natural populations of Callosobruchus maculatus.
• Comparing rMF values at benign (29°C) and stressful (36°C) temperatures.
• Analyzing the fitness of isofemale lines under different thermal conditions.

Main Results:

• One population showed substantial IaSC at 29°C (rMF = -0.51), which was significantly reduced and reversed at 36°C (rMF = 0.21).
• The second population exhibited low IaSC at both temperatures (rMF = 0.38 and 0.40).
• Lines with male-beneficial, female-detrimental alleles at benign conditions had low fitness under stress.

Conclusions:

• IaSC is reduced under environmental stress, supporting the hypothesis that stress exposes conditionally deleterious mutations to selection.
• Environmentally sensitive alleles, particularly those favored by sexual selection in males, appear to mediate changes in IaSC.
• These findings have implications for understanding adaptive evolution in sexually reproducing organisms facing environmental change.