Isotopic variation across the Audubon's-myrtle warbler hybrid zone

Area of Science:

• Ecology
• Evolutionary Biology
• Ornithology

Background:

• Seasonal migration is crucial for reproductive isolation in many species.
• Stable isotopes effectively track bird origins and movements.
• Hybrid zones offer insights into speciation processes.

Purpose of the Study:

• To investigate migratory patterns of Audubon's warblers, myrtle warblers, and their hybrids using stable hydrogen isotopes.
• To determine if migratory divides contribute to reproductive isolation between these species.
• To assess the wintering locations of hybrid warblers.

Main Methods:

• Stable hydrogen isotope analysis of warbler feathers.
• Comparison of isotopic signatures from breeding and wintering grounds.
• Analysis of migratory patterns in parent species and their hybrids.

Main Results:

• Audubon's and myrtle warblers from distinct breeding populations winter in different locations.
• Most hybrid warblers overwinter in the southeastern USA, similar to myrtle warblers.
• Some hybrids exhibit Audubon's-like migratory patterns, indicating a complex migratory divide.

Conclusions:

• A migratory divide exists between Audubon's and myrtle warblers, but it is not perfectly aligned with their breeding hybrid zone.
• Hybrid warblers' migratory behavior may influence gene flow and reproductive isolation.
• Stable isotopes are valuable tools for studying migratory connectivity in hybridizing species.