Contamination effects on sexual selection in wild dung beetles

Area of Science:

• Ecology
• Evolutionary Biology
• Environmental Science

Background:

• Sexual selection drives the evolution of costly secondary sexual traits, acting as honest indicators of individual quality.
• Contamination by environmental pollutants may disrupt these honest signals and affect population dynamics.

Purpose of the Study:

• To investigate how herbicide and veterinary drug contamination affects male dung beetle sexually selected traits (horn size, allometry) and population-level parameters (abundance, sexual size dimorphism).
• To explore the implications of these effects for species persistence in contaminated environments.

Main Methods:

• Field sampling of dung beetles across 19 pastures with varying contamination levels.
• Measurement of male horn size, condition dependence, and allometry in three dung beetle species.
• Assessment of population abundance and sexual size dimorphism in relation to chemical contamination.

Main Results:

• Horn size was generally independent of contamination, but allometric relationships were altered by herbicide and ivermectin exposure.
• Herbicide contamination reduced positive allometry in *Copris incertus* and *Digitonthophagus gazella*, while ivermectin increased it in *C. incertus*.
• Contaminated pastures showed higher abundance of large-horned *C. incertus* males, and chemical compounds affected sexual size dimorphism across all three species.

Conclusions:

• Environmental contamination interferes with sexual selection processes, altering investment in sexually selected traits and population structure.
• Sexual selection may play a role in species adaptation or persistence within contaminated ecosystems.
• Further research is needed to understand the long-term consequences of chemical pollution on sexual selection and biodiversity.