Abstract: 【Aim】In recent years, extreme weather events have increased markedly in frequency in China and globally, with many regions experiencing substantially prolonged periods of elevated summer temperatures. During field surveys, we unexpectedly discovered a rare wild yellow morph of Acyrthosiphon pisum, but its biological characteristics remain uncharacterized. This study aims to investigate the ecological adaptability and survival risks of this novel color morph of A. pisum under intensified climate change, with the goal of providing a theoretical foundation for elucidating the evolutionary mechanisms of A. pisum and informing future population management and biological control strategies.【Methods】The competitive abilities of the wild yellow morph of A. pisum against those of the red and green morphs of A. pisum on three host plants (Vicia faba, Vicia sativa, and Medicago sativa) were first compared, and the starvation tolerance of apterous viviparous adults across all the three morphs of A. pisum under conditions of food deprivation were evaluated. The three color morphs of A. pisum were subsequently subjected to repeated high-temperature stress (35 ℃ for 2 h per day until adult stage) beginning at the 1st instar nymphal stage, and the changes in their population decline rates and fecundity were detected at the adult stage. Finally, the predation risk of the 3rd instar nymphs of each color morph of A. pisum by adult female Coccinella septempunctata was assessed, and the color differences (ΔE) between the body surfaces of the 3rd instar nymphs of various morphs of A.pisum and the leaves of V. faba leaves were analyzed.【Results】The yellow morph of A. pisum showed significantly lower competitive abilities than the red and green morphs of A. pisum on V. faba and M. sativa, but occasionally attained a competitive advantage over the red morph of A. pisum on V. sativa. Compared with the other color morphs of A. pisum, the yellow morph of A. pisum demonstrated greater starvation tolerance. After heat shock treatment (35 ℃ for 2 h per day), the numbers of aphids produced by the yellow morph of A. pisum in 6 d on its native host V. sativa and the high-nutrient host V. faba were 23.83 and 31.67 individuals, respectively, which represented relatively low values as compared with those of the other two morphs of A. pisum. Specifically, these values were lower than those observed in the green morph of A. pisum on V. sativa and the red morph of A. pisum on V. faba (28.67 and 41.67 individuals, respectively). In contrast to its disadvantage in fecundity, the yellow morph of A. pisum exhibited population decline rates of 32.78% and 26.11% on V. sativa and V. faba, respectively, after heat shock treatment, both of which were lower than those recorded for the red morph of A. pisum (67.22% and 38.89% on V. sativa and V. faba, respectively) and the green morph of A. pisum (44.43% and 42.22% on V. sativa and V. faba, respectively). The color difference (ΔE) between the body surfaces of the 3rd instar nymphs of the yellow morph of A. pisum and the leaves of V. faba was 52.26, significantly greater than those between the body surfaces of the 3rd instar nymphs of the red morph of A. pisum and the leaves of V. faba (37.69), and between the body surfaces of the 3rd instar nymphs of the green morph of A. pisum and the leaves of V. faba (17.76). The yellow morph of A. pisum was more vulnerable to predation by C. septempunctata adults, with the population decline rates exceeding 49.00%.【Conclusion】The yellow morph of A. pisum exhibits distinct ecological adaptation strategies. Although the yellow morph of A. pisum is disadvantaged in competition and more vulnerable to predation, its enhanced starvation tolerance and thermal resistance may provide a fitness advantage under increasingly frequent extreme weather events.

Key words: Acyrthosiphon pisum, yellow morph, competition, survival risk, stress tolerance