LB 35-293 - Juvenile competition in bean beetles (Callosobruchus maculatus) across varying temperatures

Ectotherms are highly sensitive to temperature variation due to their inability to regulate their body temperature. Temperature effects on intraspecific competition are well-studied in theory, but experimental studies are rare. Given that intraspecific competition is the mechanism underlying population regulation, experiments that investigate temperature effects on competition are necessary in order to predict population viability in the face of climate warming. We investigated temperature and parental density effects on larval competition in the bean beetle (Callosobruchus maculatus), a pest of stored products. We measured eggs laid on individual beans, the number of larva burrowed into these beans, and the number of adults emerged. We performed this experiment at 7 temperature treatments between 18-36 ℃ and 5 parental densities (1, 2, 4, 8, and 16 pairs). These experiments revealed a significant negative effect of adult density on the birth rate. We also found a combined effect of parental density and temperature on offspring maturation rate. After calculating the population growth rate, we found that temperature displays an antagonistic relationship with competition. Because C. maculatus is a model organism, these results provide guidelines for elucidating how climate warming may affect population regulation in other ectotherms. Given that C. maculatus is a destructive pest of dried legumes, failure of population regulation due to climate warming could pose a threat for food security.