Benefits of heterospecific aggregation on necromass: influence of temperature, group density, and composition on fitness-related traits

Necrophagous blowflies (Diptera: Calliphoridae) such asCalliphora vicina, a cold-tolerant species, andLucilia sericata, a warm-adapted species, are pioneer carrion-breeder. Although these two species have different temperature preferences, larvae aggregate actively and often feed simultaneously on carrion. The hypothesis to be tested was thatL. sericatabenefits from the association withC. vicinaat lower temperatures (i.e., 15 degrees C) and thatC. vicinaderives greater benefits from this association at higher temperatures (i.e., 28 degrees C). Therefore, both species were raised at these two constant temperatures from first instars to adults under three different conditions: monospecific low-density, monospecific high-density, and heterospecific high-density. The time until larval migration, surface area of puparia, and survival rates were determined for each condition. Differences between these fitness-related traits were found between species, temperatures, group densities, and species compositions. At 28 degrees C,C. vicinalarvae bred in heterospecific groups migrated significantly earlier and in higher numbers than that under same density conspecific conditions, with a lower mortality rate. At 15 degrees C, both species benefited from high-density heterospecific associations, expressed by faster development and larger puparia. In conclusion, necrophagous larvae benefited from heterospecific aggregations at suboptimal temperatures by adapting their migration time to that of the faster species. Since temperature changes throughout the day and over the year, the beneficiary of such a collective association also changes. The costs involved and deviations to the temperature-size rule highlight the complexity of the carrion ecosystem.

Automated summary

The study found that necrophagous blowflies larvae benefit from heterospecific aggregations at suboptimal temperatures, adapting their migration time to that of the faster species. Higher densities of different species led to faster development and larger puparia, highlighting the complexity of the carrion ecosystem.