Inbreeding depression in male gametic performance

Area of Science:

• Evolutionary ecology
• Reproductive biology
• Genetics

Background:

• Inbreeding depression affects fitness components, with male fertilization success being a key area.
• Male gametic performance (sperm/pollen) is crucial for fertilization, but inbreeding effects are poorly understood.
• The impact of inbreeding on haploid gametes, despite inbreeding depression being a diploid trait, remains unclear.

Purpose of the Study:

• To assess the magnitude of inbreeding depression in male gametic performance.
• To review existing literature on inbreeding effects on sperm and pollen quantity, quality, and competitiveness.
• To understand the implications for fertilization success and inbreeding avoidance strategies.

Main Methods:

• Systematic review and meta-analysis of published studies estimating inbreeding depression in male gametic traits.
• Compilation of data across 183 traits from 51 independent studies.
• Analysis of inbreeding load in sperm and pollen performance metrics.

Main Results:

• The overall inbreeding load in male gametic performance was estimated at approximately one haploid lethal equivalent.
• Inbreeding depression was evident across diverse species and various gametic traits (quantity, quality, competitiveness).
• A significant lack of data from wild populations was identified.

Conclusions:

• Inbreeding substantially depresses male gametic performance, with significant implications for fertilization success.
• The findings highlight the importance of considering gametic performance in evolutionary ecology and conservation.
• Further research is needed on wild populations and the mechanisms (haploid vs. diploid expression) underlying gametic inbreeding depression.