Reproductive isolation caused by visual predation on migrants between divergent environments

Area of Science:

• Evolutionary Biology
• Ecology
• Speciation

Background:

• Natural selection drives adaptation and can lead to speciation via reproductive isolation.
• Cryptic coloration is a widespread adaptation, but its role in speciation is less understood.
• Divergence in coloration may impact gene flow between populations.

Purpose of the Study:

• To investigate if population divergence in cryptic coloration contributes to reproductive isolation.
• To determine the role of predation in selection on coloration morphs across different host plants.
• To assess the contribution of selection against migrants to overall premating isolation.

Main Methods:

• A manipulative field experiment with walking-stick insects assessed survival of different color morphs on various host plants under predation.
• Analysis of natural populations examined color-pattern morph frequencies in relation to host plant adaptation.
• Comparison of selection against migrants with existing estimates of sexual isolation.

Main Results:

• Survival of color morphs was dependent on host plant and avian predation.
• Migrants between host plants were more likely to be less cryptic locally.
• Selection against less-cryptic migrants significantly reduced interbreeding, contributing substantially to premating isolation.

Conclusions:

• Divergence in cryptic coloration, driven by host-specific predation, can cause reproductive isolation.
• Selection against migrants between environments plays a significant role in speciation.
• Cryptic coloration is a key factor in natural selection leading to new species formation.