Discriminating males alter sperm production between species

Area of Science:

• Reproductive biology
• Evolutionary biology
• Speciation

Background:

• Prezygotic reproductive isolation is crucial for speciation.
• Sperm competition theory highlights post-mating, pre-fertilization mechanisms.
• The role of sperm production costs in species isolation is understudied.

Purpose of the Study:

• To investigate differential sperm production in sailfin mollies (Poecilia latipinna).
• To determine if sperm production varies based on the presence of conspecific versus gynogenetic (Poecilia formosa) females.
• To explore the link between sperm production, mate choice, and prezygotic isolation.

Main Methods:

• Examined sperm production in male sailfin mollies exposed to conspecific females versus gynogenetic females.
• Compared sperm production levels between allopatric and sympatric populations.
• Assessed male mate choice for conspecific over heterospecific females.

Main Results:

• Males produced significantly more sperm when in the presence of conspecific females compared to heterospecific females.
• This pattern of differential sperm production was consistent in both allopatric and sympatric populations.
• Male mate choice for conspecifics was reflected in sperm production levels.

Conclusions:

• Differential sperm production, influenced by mate choice, is a factor in prezygotic reproductive isolation.
• This mechanism may play a role in the speciation of bisexual species complexes, particularly in sympatry.
• Sperm production costs are a relevant, yet often overlooked, aspect of reproductive isolation studies.