Do density-driven mating system differences explain reproductive incompatibilities between populations of a placental...

Area of Science:

• Evolutionary Biology
• Reproductive Biology
• Genetics

Background:

• Matrotrophy, or maternal provisioning of embryos, can lead to mother-embryo conflict over resource allocation.
• This conflict is hypothesized to drive reproductive isolation between populations with differing mating systems.
• Previous studies noted asymmetric reproductive isolation in the least killifish (Heterandria formosa).

Purpose of the Study:

• To investigate if density-driven mating system differences explain asymmetric reproductive isolation in Heterandria formosa.
• To assess the role of multiple paternity in reproductive isolation within this matrotrophic species.

Main Methods:

• Minimum sire number reconstructions were used to analyze paternity in four populations of Heterandria formosa.
• Genetic variation levels were considered to account for potential biases in detecting multiple mating.
• Analysis focused on concurrent multiple paternity within broods and across distinct broods.

Main Results:

• Initial analyses suggested lower multiple paternity in low-density populations, but this was influenced by reduced genetic variation.
• After accounting for genetic variation, high levels of multiple paternity were common across all populations.
• In the most powerfully analyzed population, multiple paternity involved multiple sires within single broods, often skewed towards one father.

Conclusions:

• Differences in multiple paternity levels alone do not sufficiently explain the observed reproductive isolation in Heterandria formosa.
• Other factors influencing maternal-embryo conflict may contribute to reproductive isolation.
• Asymmetric reproductive isolation might arise from disrupted maternal-embryo coadaptation.