Stabilization of a salamander moving hybrid zone

Area of Science:

• Ecology
• Evolutionary Biology
• Conservation Biology

Background:

• Hybrid zones form when related species expand their ranges and meet.
• These zones are predicted to move until equilibrium is reached.
• A moving hybrid zone between Triturus cristatus and Triturus marmoratus in France was previously documented.

Purpose of the Study:

• To identify ecological factors influencing the hybrid zone of Triturus cristatus and Triturus marmoratus.
• To investigate the reasons for the observed stalling of this hybrid zone.
• To understand the impact of landscape changes on hybrid zone dynamics.

Main Methods:

• Ecological niche modeling to identify habitat correlates.
• Analysis of historical and current hybrid zone positions.
• Assessment of landscape changes, specifically hedgerow and pond dynamics.
• Population density and connectivity analysis.

Main Results:

• Elevation, forestation, and hedgerows favor T. marmoratus; pond density favors T. cristatus.
• The hybrid zone moved approximately 30 km between 1950-1979, likely due to postwar bocage reduction.
• No hybrid zone movement has been observed since 1979.
• Pond loss rates of 5.5% per year due to agricultural intensification are documented.
• Habitat fragmentation and reduced population densities are identified as likely causes for the hybrid zone stall.

Conclusions:

• The stalling of the Triturus hybrid zone is likely caused by habitat loss and fragmentation driven by agricultural intensification.
• Reduced pond availability and population isolation impede further hybrid zone movement.
• Conservation efforts may need to address habitat restoration to facilitate natural processes.