Conspecific sperm precedence in Drosophila

Area of Science:

• Evolutionary Biology
• Reproductive Biology
• Speciation

Background:

• Traits influencing male-female interactions evolve rapidly via sexual selection and sexually antagonistic coevolution.
• Divergence in fertilization systems can lead to reproductive incompatibilities and speciation.
• Postmating isolation mechanisms are crucial for understanding species boundaries.

Purpose of the Study:

• To investigate cryptic reproductive divergence and postmating isolation among three sibling Drosophila species.
• To determine the role of seminal fluid and female choice in sperm precedence.
• To explore the mechanisms underlying sperm competition and fertilization success.

Main Methods:

• Conducted mating experiments with conspecific and heterospecific males and females.
• Analyzed fertilization success after single and sequential mating events.
• Utilized experiments with spermless males to isolate the effect of seminal fluid.

Main Results:

• Females exhibited conspecific sperm precedence, fertilizing the majority of eggs regardless of mating order.
• Heterospecific sperm fertilization success decreased in double matings compared to single matings.
• Conspecific seminal fluid was identified as a key factor in sperm precedence.
• Sequential mating between different species resulted in variable sperm precedence patterns, unlike consistent within-species patterns.

Conclusions:

• Females actively mediate sperm competition, influencing fertilization outcomes.
• Second-male sperm precedence is not solely a mechanical process but is influenced by female-mediated factors.
• Cryptic reproductive divergence in fertilization systems contributes to reproductive isolation and potentially speciation in Drosophila.