Winner-loser effects on life history traits

Area of Science:

• Evolutionary biology
• Animal behavior
• Gerontology

Background:

• Aging in male animals can be influenced by reproductive demands and social competition.
• Distinguishing the effects of mating effort versus fighting is complex due to their correlation.

Purpose of the Study:

• To investigate the interactive effects of fighting (winning/losing) and reproductive effort (access to females) on male mosquitofish aging.
• To understand how social dynamics and reproductive investment affect future reproductive allocation and somatic maintenance.

Main Methods:

• A 2x2 experimental design was employed over 9 weeks.
• Mosquitofish males were subjected to conditions of winning/losing fights and high/low reproductive effort.
• Telomere length and life-history traits (mating effort, ejaculates) were measured.

Main Results:

• Winners showed different mating effort than losers, but ejaculates were unaffected.
• Higher past reproductive effort correlated with lower current mating effort and slower growth.
• Sperm swimming speed was reduced in males with higher past reproductive effort, particularly smaller individuals.
• Neither high reproductive effort nor losing fights led to shorter telomeres.

Conclusions:

• Past social interactions significantly influence how male mosquitofish allocate resources between reproduction and somatic maintenance.
• Reproductive effort and social status are key factors modulating male aging and resource allocation strategies.
• Telomere length may not be a direct indicator of aging under these specific experimental conditions.