Selection-Based Biodiversity at a Small Spatial Scale in a Low-Dispersing Insular Bird

Area of Science:

• Ecology
• Evolutionary Biology
• Ornithology

Background:

• Blue tits (Cyanistes caeruleus) exhibit high mobility and inhabit diverse oak forests.
• Gene flow in mainland populations can lead to maladaptive breeding timing in rarer evergreen oak habitats.

Purpose of the Study:

• To investigate the evolutionary consequences of habitat diversification and isolation on blue tit populations.
• To assess whether gene flow homogenizes traits or promotes local adaptation in insular populations.

Main Methods:

• Comparative analysis of breeding and morphological traits between blue tit populations on Corsica.
• Assessment of gene flow effects in relation to habitat types (deciduous vs. evergreen oaks).

Main Results:

• Corsican blue tit populations, despite being geographically close (25 km), show high specialization for different oak habitats.
• Populations differ in breeding and morphological traits, indicating local adaptation rather than homogenization by gene flow.
• This contrasts with mainland populations where gene flow leads to maladaptive breeding timing.

Conclusions:

• Habitat diversification and small-scale isolation can drive significant evolutionary divergence in insular organisms.
• Conservation policies for island species should consider the evolutionary consequences of habitat heterogeneity and isolation.
• The findings challenge the assumption of gene flow as a purely homogenizing force in evolutionary processes.