Early-acting inbreeding depression can evolve as an inbreeding avoidance mechanism

Area of Science:

• Evolutionary Biology
• Population Genetics
• Reproductive Biology

Background:

• Self-fertilization, though often avoided, is inevitable in many plant and animal species.
• Inbreeding depression, a reduction in fitness due to mating with relatives, is a significant consequence.
• Existing mechanisms for preventing selfing are not always fully effective.

Purpose of the Study:

• To investigate the evolutionary dynamics of inbreeding depression in species with incidental self-fertilization.
• To explore how reproductive compensation influences selection on inbreeding depression.
• To determine if selection can favor mechanisms that actively reduce the fitness of inbred offspring.

Main Methods:

• Developed a theoretical model analyzing the effects of reproductive compensation on inbreeding depression.
• Simulated selection pressures under varying rates of self-fertilization and embryo loss.
• Identified conditions under which deleterious recessive variants can be favored by selection.

Main Results:

• Selection can favor 'self-sacrificial' variants that cause inbred embryos to die early when reproductive compensation is present.
• This mechanism challenges the assumption that all inbreeding depression is maladaptive.
• The model generates testable predictions for species with high selfing rates and strong inbreeding depression.

Conclusions:

• Inbreeding depression may not always be purely detrimental; it can be adaptive under specific conditions.
• Self-sacrificial embryo death is a potential evolutionary strategy to mitigate the fitness costs of inbreeding.
• This theory may explain low realized selfing rates in gymnosperms, which exhibit high primary selfing rates and strong inbreeding depression.