Trophic ecology of citrus pests based on stable isotope analysis

Abstract

Macrodactylus pumilio Burm. (Coleoptera: Scarabeidae) and Naupactus cervinus (Boh.) (Coleoptera: Curculionidae) are considered primary pests in citrus crops in Brazil, causing damage to plants and decreasing productivity. However, few studies investigate the ecology of these insects. In this context, the use of stable isotopes analysis (SIA) emerges as an alternative technique to conventional studies of behavioral ecology because it is faster and may explain feeding behavior based on the food source for each species. Field sampling and laboratory experiments were carried out to examine the changes of carbon and nitrogen stable isotope ratios (δ 13 C and δ 15 N) among pests and host plants (C 3 citrus and C 4 grasses), providing means to examine trophic interactions. Beetles were collected at the municipality of Gavião Peixoto, São Paulo State, identified and kept at 5 °C in saturated saline solution until the SIA. Two patterns for both species were found: δ 13 C value for N. cervinus was-23.6 ‰ and-13 ‰ for M. pumilio, indicating similarity between the results of δ 13 C of N. cervinus and citrus plants (-26 ‰) and dependence on grasses (-12 ‰) for M. pumilio individuals. The mean δ 15 N value was 4.3 and 5.8 ‰ for citrus plants and grass leaves, respectively, and the mean δ 15 N value was 4.4 ‰ for N. cervinus and 4.9 ‰ for M. pumilio. The results showed a higher affinity of N. cervinus for citrus roots since the larval stage compared with the alternative diet on M. pumilio.

Elucidating the trophic role of Tapinoma ibericum (Hymenoptera: Formicidae) as a potential predator of olive pests

“…This technique has the potential to track energy or mass flow through ecological communities and help to discern complex trophic interactions, such as omnivory (Post, 2002). Studying the natural abundance of SI allowed us to evaluate trophic relationships (Morente & Ruano, 2022), infer animal diet types (Santi‐Júnior et al, 2018) and assess species interactions (Caut et al, 2009). However, to do so, it is important to know the isotopic enrichment rate, which may change in different species (Quinby et al, 2020; Spence & Rosenheim, 2005), as well as the time needed for isotopes to be incorporated in the tissues of our species of interest (Franssen et al, 2017).…”

Stable isotope ecology in insects: a review

“…Most SIA studies are considered natural abundance studies because they exploit the natural variations in stable isotope signatures within ecosystems. Variation in the natural abundance of isotope ratios create spatial and temporal patterns that allow estimations of habitat use (Post, 2002), track nutrient flow (Collier et al ., 2002), evaluate nutritional status (Gannes et al ., 1998), determine nutrient assimilation into tissue (Tieszen & Fagre, 1993), evaluate trophic relationships (Santi‐Júnior et al ., 2018), estimate animal diets (Divine et al ., 2017;), assess species interactions (Caut et al ., 2006), and determine animal movements (Vander Zanden et al ., 2015). In contrast, SIA studies using artificially enriched isotopic compounds as tracers are referred to as enrichment studies (see McDermott et al ., 2019).…”