THE DYNAMICS OF TWO HYBRID ZONES IN APPALACHIAN SALAMANDERS OF THE GENUS PLETHODON

Area of Science:

• Ecology
• Evolutionary Biology
• Herpetology

Background:

• Hybrid zones provide insights into evolutionary processes.
• Understanding intergradation dynamics is crucial for conservation.
• Plethodon salamanders are key model organisms in ecological studies.

Purpose of the Study:

• To investigate the dynamics of two Plethodon salamander hybrid zones.
• To determine the factors influencing the stability or spread of hybrid zones.
• To assess the role of environmental changes and human disturbances in hybridization.

Main Methods:

• Long-term monitoring (18-20 years) of two Plethodon hybrid zones.
• Systematic scoring of coloration traits in salamander populations twice annually.
• Elevation-based transect sampling to analyze character distribution.

Main Results:

• One hybrid zone (Balsam Mountains) remained stable with no significant changes in coloration scores over time.
• The other hybrid zone (Nantahala Mountains) showed a significant upward spread of Plethodon jordani characters.
• The rate of spread in the Nantahala Mountains suggests selection, not random diffusion, is the primary driver.

Conclusions:

• The stability of the Balsam Mountains zone may be due to neutral character evolution and random diffusion.
• The upward spread in the Nantahala Mountains indicates selection favoring Plethodon glutinosus traits, possibly linked to post-timbering environmental changes.
• Human disturbances, such as intense timbering, may initiate or influence the dynamics of hybrid zones in Plethodon.