Frequency-Dependent Hybridization Contributes to Habitat Segregation in Monkeyflowers

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Spatial segregation of species is often linked to differing stress tolerance and competitive abilities.
• Reproductive interactions can impose fitness costs, particularly on rarer species within mixed populations.
• Frequency-dependent mating may limit immigrant establishment and maintain species segregation.

Purpose of the Study:

• To test the hypothesis that frequency-dependent mating disadvantage maintains spatial segregation in sympatric monkeyflowers (Mimulus nudatus and Mimulus guttatus).
• To evaluate the role of reproductive interference in natural immigration and species coexistence.

Main Methods:

• Conducted two field experiments involving immigrant additions to heterospecific-dominated sites.
• Performed reciprocal transplant experiments with varying frequencies of resident and immigrant plants.
• Assessed immigrant seed viability and overall success under different population densities.

Main Results:

• Immigrant seed viability declined with conspecific rarity for Mimulus guttatus but not Mimulus nudatus.
• Both species experienced an immigrant minority disadvantage.
• This disadvantage stemmed from frequency-dependent hybridization in M. guttatus and resource/pollinator competition in M. nudatus.

Conclusions:

• Reproductive interference plays a significant role in maintaining spatial segregation between these monkeyflower species.
• Findings suggest that reproductive interference should be considered alongside stress tolerance and competitive ability in ecological segregation studies.
• The study highlights differential mechanisms of reproductive interference impacting species coexistence.