Rising temperatures affect the interspecific interference competition between Harmonia axyridis and Propylea japonica, and their predation rate on Myzus persicae.

Rising temperatures can enhance foraging activity and accelerate the encounter rate of different predators, which may increase their interference competition strengths. However, limited information is available on such effects of temperature, and on the consequences for their predation rates. We used a functional response approach to experimentally quantify the interspecific interference competition strength of two species of ladybirds, Harmonia axyridis and Propylea japonica (Coleoptera: Coccinellidae), toward their prey Myzus persicae (Hemiptera: Aphididae) at 23 and 33 °C, respectively. The results indicated that high temperature could cause P. japonica to be more active and interfere with H. axyridis more often, and strengthened the interference competition between these two predators. The functional response of H. axyridis was changed from type II in single H. axyridis treatment to type III in paired predator assays at 23 and 33 °C. Moreover, single H. axyridis consumed more aphids than H. axyridis in heterospecific predator trials at aphid densities below 50 and 35 at 23 and 33 °C treatments, respectively. For P. japonica, type II functional responses were detected in all assays. Additionally, when competing with H. axyridis, the predation rate of P. japonica at 23 °C was almost unchanged compared to that of single P. japonica, but fewer aphids were eaten compared with single P. japonica across all aphid densities at 33 °C. Thus, with interference competition, two predator species respond differently to temperature changes in terms of foraging efficiency, which may further affect the population adaptability and control efficiency of these two focal species. [ABSTRACT FROM AUTHOR]