Rapid evolution by sexual selection in a wild, invasive mammal

Area of Science:

• Evolutionary biology
• Sexual selection
• Behavioral ecology

Background:

• Sexual selection theory typically focuses on direct mate interactions.
• Ecological factors can significantly influence the evolution of sexually selected traits.
• The small Indian mongoose (Urva auropunctata) provides a model for studying rapid evolutionary change in introduced populations.

Purpose of the Study:

• To investigate the impact of ecological changes on sexually selected traits in the small Indian mongoose.
• To compare sexual traits between the native range and introduced invasive populations.
• To test predictions regarding changes in male scent marking and testis size.

Main Methods:

• Comparative analysis of sexually selected traits in native and introduced small Indian mongoose populations.
• Measurement of anal pad size (scent marking) and testis size in relation to time since introduction and population density.
• Assessment of trait relationships with body size and condition.

Main Results:

• Male anal pad size decreased significantly in introduced populations, correlating with time since introduction and population density.
• The relationship between anal pad size and body size/condition weakened in introduced populations.
• Testis size increased in introduced populations, consistent with intensified sperm competition.

Conclusions:

• Ecological factors, such as increased encounter rates and altered mating competition, can drive rapid evolutionary changes in sexual traits.
• The small Indian mongoose exhibits rapid adaptation in response to invasion, with an inversion in the relative importance of different sexual traits.
• This study highlights the dynamic interplay between ecology and sexual selection in shaping evolutionary trajectories.