Does the host shift affect the body size of the rice weevil (Sitophilus oryzae L.) as a response to developmental stress: Wheat-Maize-Sorghum case?

Abstract

The rice weevil, Sitophilus oryzae (L.) is recognised as one of the most polyphagous and extremely destructive pests of stored cereal grains worldwide. It develops under a wide range of environmental conditions, however, there have been some indications about alterations in specimen morphology when observed across populations originating from different commodities. While responses to different stressors have mainly been evaluated using survival, progeny production, and developmental time, body size as an indicator of developmental stress has received limited attention. This study investigated whether centroid size (CS), assessed through geometric morphometrics, reflects the influence of hosts changes, i.e whether these responses are associated with seed traits. A parental population reared on wheat was transferred to maize and sorghum, and progeny production and body size were analysed. Adults from maize were statistically significantly smaller than those from wheat, despite similar progeny production. Sorghum significantly reduced progeny production but did not significantly affect body size. Phenotypic variability in CS was the highest in the maize population. According to two-block Partial Least Squares analysis, larger body size was associated with higher protein content, while seed hardness and increased total phenolic contents, including flavonoids and tannins, were linked to reduced CS. These results indicate that body size must be measured as an indicator of developmental responses. Also, our study suggests the importance of integrating complementary biological parameters to provide a more comprehensive understanding of developmental responses to host shifts and other stressors, and helps to identify host characteristics associated with insect performance.