The ecological-evolutionary interplay: density-dependent sexual selection in a migratory songbird

Area of Science:

• Ecology
• Evolutionary Biology
• Ornithology

Background:

• Environmental heterogeneity influences species' spatial dynamics and adaptive evolution.
• Human-dominated landscapes create novel environmental conditions affecting ecological interactions.
• Sexual selection is a key evolutionary process sensitive to ecological factors.

Purpose of the Study:

• To investigate how environmental heterogeneity in suburban landscapes affects reproductive strategies and sexual selection.
• To determine if suburban matrix (SM) and suburban parks (SP) differentially influence sexual selection.
• To identify ecological factors driving spatial variation in sexual selection.

Main Methods:

• Studied gray catbirds in suburban matrix and park habitats.
• Assessed breeding density, reproductive strategies, and nesting success (within-pair and extra-pair offspring).
• Analyzed body size as a predictor of reproductive success and directional selection.

Main Results:

• Breeding density varied between suburban matrix and park habitats.
• Local breeding density predicted the likelihood of extra-pair offspring.
• Extra-pair success increased sexual selection opportunities by 39% at higher densities.
• Body size was a strong predictor of reproductive success and under directional selection in both habitats.
• Sexual selection strength did not differ at the landscape scale but was influenced by fine-scale breeding density.

Conclusions:

• Breeding density, a fine-scale ecological factor, drives density-dependent sexual selection in gray catbirds.
• Anthropogenic habitat modification creates heterogeneity that alters fine-scale ecological conditions influencing sexual selection.
• This study documents density-dependent sexual selection in a migratory bird within human-modified landscapes.