Temporal population genetic instability in range-edge western toads, Anaxyrus boreas

Area of Science:

• Ecology
• Evolutionary Biology
• Population Genetics

Background:

• Range-edge populations are crucial for understanding species' responses to environmental changes.
• Continual colonization events can influence population genetic structure.
• Temporal stability of genetic structure is key to long-term population viability.

Purpose of the Study:

• To assess the temporal stability of population genetic structure in western toads (Anaxyrus boreas) at their northern range limit.
• To investigate the impact of short-distance colonization on genetic relationships among breeding populations over two seasons.
• To determine if genetic differentiation occurs within ponds between years.

Main Methods:

• Field sampling of western toad breeding populations across 20 ponds in southeast Alaska over two consecutive summers (2008 and 2009).
• Genetic analysis of sampled individuals to determine population structure and relationships.
• Comparison of genetic data between years for ponds sampled in both seasons (14 ponds).

Main Results:

• Considerable turnover in population genetic relationships among ponds was observed between the two sampling seasons.
• Biologically meaningful genetic differentiation was detected within some ponds between years.
• Consistent genetic relationships were found among major population centers, while relationships with smaller, outlying populations varied annually.

Conclusions:

• The genetic landscape of range-edge populations can be dynamic, with significant year-to-year variation.
• Temporal instability in genetic structure, particularly with outlying populations, suggests ongoing colonization and gene flow.
• Multi-year genetic sampling is essential for accurately characterizing the genetic structure and connectivity of populations experiencing colonization events.