Inter- and intraspecific variation in cannibalism in seed bugs (Hemiptera: Lygaeidae)

Whilst common across the animal kingdom, the evolution of cannibalism remains poorly understood. Part of the problem is that the number of taxonomic groups in which the evolution of cannibalism has been studied in detail is limited, leaving us with only patchy data to explore trends across species. In this study, we consider within and between species variation in cannibalism in four species of seed bug with similar but not identical ecologies. Looking first at the influence of developmental stage on cannibalism, we show that cannibalism is generally most common in juvenile stages of these species, being especially pronounced in some cases early in life (when further dispersal is likely typically needed to locate host plants). Closer examination of one of these species, Spilostethus pandurus, suggests that cannibalism has evolved specifically as an adaptation to early life survival and not a general trait for starvation resistance across the lifetime. Cannibalism propensity was also observed to depend on early life experience of conspecifics in this species, suggesting a role for environmental variation in shaping this behaviour. These results highlight that if we are to understand trends in cannibalism across the animal kingdom, we must consider the ecological causes of variation in cannibalism within and between species.