Directional postcopulatory sexual selection revealed by artificial insemination

Area of Science:

• Evolutionary Biology
• Sexual Selection
• Animal Behavior

Background:

• Postcopulatory sexual selection includes sperm competition and cryptic female choice.
• Few studies link attractive male traits to post-insemination success.
• Pre- and post-insemination selection interact, influencing paternity variation.

Purpose of the Study:

• To investigate if precopulatory sexual selection (male attractiveness) influences postcopulatory success.
• To determine if female mating preferences are reinforced by physiological post-insemination processes.
• To examine the role of male traits in sperm competition.

Main Methods:

• Artificial insemination was used to control for pre-insemination factors.
• Equal numbers of sperm from two competing males were used.
• Guppy (Poecilia reticulata) parentage was analyzed based on male coloration.

Main Results:

• Colorful male guppies achieved greater parentage when sperm competed.
• This indicates female mating preferences can be reinforced post-insemination.
• Smaller male size was associated with an advantage in sperm competition.

Conclusions:

• Male attractiveness can confer a postcopulatory fertilization advantage.
• Physiological mechanisms at the post-insemination stage reinforce precopulatory mate choice.
• A potential trade-off exists between sperm competitiveness and somatic growth in male guppies.