Behavioral Responses of Chrysoperla defreitasi (Neuroptera: Chrysopidae) and Myzus persicae (Hemiptera: Aphididae) to Volatile Compounds from Wild and Domesticated Ugni molinae

Abstract

Domestication significantly altered the phenotypic and chemical traits of murtilla, notably reducing the emission of volatile compounds essential for plant-insect interactions. This reduction may affect the plant's natural defense mechanisms, influencing its interactions with herbivores and predators. Therefore, this study tests whether domestication reduces volatile emissions in murtilla, increasing aphid preference and decreasing lacewing attraction. We selected wild ancestors (19-1, 22-1, and 23-2) from a longterm Ugni molinae germplasm bank. Crosses between these wild ancestors generated four first-generation domesticated ecotypes, 10-1, 16-16, 17-4, and 66-2, used in this study. These first-generation domesticated ecotypes were six years old at the time of the study and were used for comparisons in volatile profile and insect interaction analyses. The olfactometric preference index (OPI) for lacewing larvae and aphids revealed that wild ancestors attracted more predators than domesticated plants. For example, Ecotype 19-1 had an OPI of 1.64 for larvae and 1.49 for aphids, while Ecotype 10-1 showed lower attraction (OPI of 1.01 for larvae and 1.00 for aphids). Gas chromatography analysis identified differences in volatile organic compounds, with wild ancestor ecotypes emitting higher levels of compounds such as 2-hexanone, 1,8-cineole, and α-caryophyllene. Principal component analysis and hierarchical clustering confirmed these chemical distinctions. In olfactometer assays, lacewing larvae preferred α-caryophyllene and 2,4-dimethyl acetophenone, while aphids favored 2-hexanone and 3-hexanol. In Y-tube assays, lacewing adults showed strong attraction to α-pinene and 2,4-dimethyl acetophenone, with preferences increasing with concentration. These results indicate that domestication altered the volatile murtilla profile, reducing its attractiveness to natural predators while increasing its susceptibility to herbivores, supporting the plant domestication defense theory.

Keywords: VOCs; aphid; chemical ecology; insect–plant interactions; lacewing; plant domestication.

Figure 1

Total emission of volatile organic compounds in wild and domesticated Ugni molinae plants (µg/g/cm²/day). Different letters indicate statistically significant differences between groups according to the t-test (p < 0.05). Bars represent means ± SE.

Figure 2

Principal component analysis of volatile organic compounds in cultivated ecotypes and wild ancestors of murtilla. (A) Separation between domesticated ecotypes and ancestors based on the first two principal components. (B) Distribution of VOCs according to their contribution to the total variability. (C) Hierarchical cluster analysis (HCA) of volatile organic compounds in murtilla. The heatmap shows the relative abundance of each compound (blue: low abundance, red: high abundance). The dendrogram groups both samples and compounds according to chemical similarity, using Ward’s linkage and Pearson correlation as the similarity index. A relative distance scale is shown at the bottom of the dendrogram.

Figure 3

Olfactometric preference index (OPI) of different ecotypes in ancestor and domesticated groups when exposed to lacewing larvae, lacewing adults, and aphid adults. Different letters indicate significant differences (p < 0.05) among treatments. Bars represent means ± SE.

Figure 4

Olfactometric preference index (OPI) for lacewing larvae and terpenes (A) and alcohols, ketones and esters (B), OPI for aphid and terpenes, (C) and alcohols, ketones, and esters (D). Different letters mean significant differences according to ANOVA analysis followed by a Tukey test (p ≤ 0.05). Points represent means ± SE.