Postmating Reproductive isolation between strains of Drosophila willistoni

Area of Science:

• Evolutionary Biology
• Genetics
• Zoology

Background:

• Speciation involves reproductive isolation barriers preventing successful reproduction.
• The Drosophila willistoni subgroup offers a model for studying speciation due to varied isolation mechanisms and genetic resources.
• Drosophila willistoni willistoni exhibits a wide distribution, with a subspecies (D. w. quechua) showing unidirectional male sterility.

Purpose of the Study:

• To investigate reproductive isolation among different strains of Drosophila willistoni willistoni.
• To determine if geographic separation correlates with genetic divergence and reproductive barriers.
• To resolve the taxonomic status of D. willistoni willistoni populations east of the Andes.

Main Methods:

• Fecundity assays were conducted on F1 hybrids from crosses between different D. willistoni strains.
• Hybrid male sterility was assessed as a measure of reproductive isolation.
• Geographic origins of strains included Central America, North America, Caribbean islands, and South America.

Main Results:

• F1 hybrid males from crosses between northern (Central America, North America, northern Caribbean) and southern (South America, southern Caribbean) strains exhibited unidirectional sterility.
• This sterility indicates a significant reproductive isolation barrier between these geographic groups.
• The findings challenge the current subspecies classification of D. willistoni willistoni.

Conclusions:

• A distinct reproductive isolation barrier, specifically unidirectional hybrid male sterility, exists between northern and southern D. willistoni strains.
• These results support the subdivision of the D. willistoni willistoni species into two distinct subspecies.
• Geographic isolation and subsequent genetic divergence have led to reproductive incompatibility within this subgroup.