Maternal effects and range expansion: a key factor in a dynamic process?

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Species in ephemeral habitats evolve specific dispersal strategies linked to colonization traits.
• Natural selection maintains these strategies due to variable resource abundance, especially during range expansion.
• Mechanisms integrating dispersal traits and generating dispersal variability remain largely unknown.

Purpose of the Study:

• Investigate the role of maternal effects in generating dispersal variability in western bluebirds during range expansion.
• Test how breeding females influence offspring dispersal phenotypes in response to fluctuating resource availability.
• Determine if maternal effects explain the alignment of dispersal strategies with resource conditions.

Main Methods:

• Studied western bluebirds (Sialia mexicana), a species dependent on ephemeral nest cavities.
• Observed offspring dispersal phenotypes in newly established populations during range expansion.
• Conducted experiments to test the link between resource availability, offspring birth order, and dispersal propensity.

Main Results:

• Breeding females alter offspring's position in the egg-laying order based on resource levels.
• Low resources lead to aggressive, dispersing males; abundant resources lead to non-aggressive, philopatric males.
• The association between resource availability and sex-specific birth order was experimentally confirmed across populations.

Conclusions:

• Maternal effects are crucial for generating dispersal variability in newly colonized populations.
• This mechanism allows western bluebirds to track resource availability, influencing range expansion dynamics.
• Maternal effects are vital for understanding colonizing phenotypes and the process of range expansion.