Variable hybridization outcomes in trout are predicted by historical fish stocking and environmental context

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Hybridization between closely related species can alter genomic composition and phenotypes.
• Understanding variation in hybridization outcomes across geographic locations is crucial for identifying reproductive isolation mechanisms.

Purpose of the Study:

• To investigate the geographic variability of hybridization outcomes between Yellowstone cutthroat trout and rainbow trout.
• To identify environmental and historical factors driving variation in hybridization patterns.

Main Methods:

• Genomic data analysis to determine hybrid ancestry.
• Hierarchical Bayesian models to precisely identify ancestry.
• Individual-based simulations to compare observed outcomes with null expectations.
• Modeling hybridization outcomes against environmental variables and stocking history.

Main Results:

• Hybridization outcomes significantly varied across 27 study locations in the North Fork Shoshone River basin.
• Observed hybridization patterns deviated from null expectations, suggesting functional reproductive isolation mechanisms.
• Fish stocking history was the primary predictor of hybridization outcomes, followed by environmental variables influencing species overlap.

Conclusions:

• Geographic variation in hybridization outcomes is substantial and influenced by external factors.
• Reproductive isolation mechanisms are active, maintaining parental taxa and hybrid diversity.
• Fish stocking history and environmental conditions play key roles in shaping hybridization dynamics and reproductive isolation.