Weapons Evolve Faster Than Sperm in Bovids and Cervids.

Area of Science:

• Evolutionary biology
• Animal behavior
• Sexual selection

Background:

• In polyandrous species, males compete for mates both before and after copulation.
• Sexual selection influences the evolution of pre- and postcopulatory traits, creating trade-offs in resource allocation.
• Examining evolutionary rates of these traits can reveal their relative importance and fitness consequences.

Purpose of the Study:

• To compare the evolutionary rates of male competitive traits in bovids (Bovidae) and cervids (Cervidae).
• To understand the relative selective pressures on pre- and postcopulatory traits in artiodactyls.
• To investigate the evolutionary patterns of weaponry, body size, testes mass, and sperm morphometrics.

Main Methods:

• Comparative analysis of evolutionary rates.
• Quantification of male weaponry (horns and antlers), body size/mass, testes mass, and sperm morphometrics.
• Assessment across two artiodactyl families: bovids and cervids.

Main Results:

• Male weaponry evolves at a faster rate than sperm dimensions.
• Testes mass and body mass exhibit similar evolutionary rates.
• Sperm head and midpiece evolve faster than the sperm flagellum, showing differential evolution within sperm.
• Evolutionary patterns were broadly consistent between bovids and cervids, despite differences in weapon development.

Conclusions:

• Both pre- and postcopulatory traits in male bovids and cervids experience strong, yet differential, sexual selection.
• The distinct evolutionary rates suggest varied selective pressures on different reproductive components.
• Comparative evolutionary rates provide insights into the adaptive strategies shaped by sexual selection in these families.