Gene flow does not prevent personality and morphological differentiation between two blue tit populations

Area of Science:

• Ecology and evolutionary biology
• Behavioral ecology
• Population genetics

Background:

• Phenotypic divergence between populations is a key area of study in ecology and evolution.
• Divergence can stem from genetic changes, phenotypic plasticity, or both.
• Mechanisms driving divergence in closely located populations with gene flow are less understood, particularly for behavioral traits.

Purpose of the Study:

• To investigate the genetic basis of phenotypic divergence in blue tit populations.
• To compare divergence in personality, physiological, and morphological traits.
• To determine if divergence is driven by selection or genetic drift.

Main Methods:

• A common garden experiment was conducted using blue tits (Cyanistes caeruleus) from two populations separated by 25 km.
• Nestlings were raised in a controlled environment for up to 5 years.
• Phenotypic traits (exploration speed, handling aggression, heart rate, tarsus length, body mass) and genetic markers (Qst, Fst) were analyzed.

Main Results:

• Phenotypic differences observed in the wild were replicated in the common garden, indicating genetic divergence for all studied traits.
• Qst-Fst comparisons suggested that divergent selection patterns, not genetic drift, are the primary drivers of these differences.
• This study provides one of the first Qst-Fst comparisons for personality traits in birds.

Conclusions:

• Small-scale genetic divergence is possible for a range of traits, including behavioral ones, in populations connected by gene flow.
• Local adaptation driven by dissimilar selection pressures plays a significant role in shaping population differences.
• The findings contribute to understanding the micro-evolutionary processes underlying phenotypic diversity.