Cryptic reproductive isolation in the Drosophila simulans species complex

Area of Science:

• Evolutionary Biology
• Genetics
• Reproductive Biology

Background:

• Postmating, prezygotic reproductive isolation is vital for speciation.
• These mechanisms, occurring after copulation but before fertilization, are understudied.
• The Drosophila simulans species complex provides a model for investigating reproductive isolation.

Purpose of the Study:

• To examine postmating, prezygotic reproductive isolation in three specific hybridizations within the Drosophila simulans species complex.
• To identify and characterize the cryptic barriers that impede heterospecific fertilization in these crosses.

Main Methods:

• Females were allowed a single mating; copulation duration was observed and timed.
• Dissections tracked sperm storage and retention in females.
• Egg production, hatchability, progeny counts, and female longevity were measured.

Main Results:

• D. simulans females mating with D. sechellia males showed limited sperm transfer.
• D. simulans females mating with D. mauritiana males experienced short copulations, reduced sperm storage, and fewer eggs.
• D. mauritiana females mating with D. simulans males had abundant sperm transfer and storage, but rapid sperm loss and inefficient utilization.

Conclusions:

• Each hybridization exhibits unique postmating, prezygotic barriers.
• These findings expand the known reproductive isolating mechanisms within the Drosophila simulans clade.
• The identified barriers contribute to understanding the evolutionary processes driving speciation.