Size-mediated priority and temperature effects on intra-cohort competition and cannibalism in a damselfly

1. A shift in the relative arrival of offspring, e.g., a shift in hatching time, can affect competition at the intraspecific level through size-mediated priority effects, where the larger individuals gain more resources. These priority effects are likely to be affected by climate warming and the rate of intraspecific predation, i.e., cannibalism. 2. In a laboratory experiment, we examined size-mediated priority effects in larvae of the univoltine damselfly, Lestes sponsa, at two different temperatures (21°C and 23°C). We created three size groups of larvae by manipulating hatching time: early hatched with a large size (extra-advanced), intermediate hatched with an intermediate size (advanced) and late hatched with a small size (non-advanced). Thereafter we reared the larvae from these groups in non-mixed and mixed groups of 12 larvae. 3. We found strong priority and temperature effects. First, extra-advanced larvae most often had higher survival, growth and development rates than non-ad...