The Ontogenetically Variable Trophic Niche of a Praying Mantid Revealed by Stable Isotope Analysis

Abstract

Praying mantids have been shown to exert strong influences on arthropod community composition. However, they may not occupy the same trophic level throughout their lives. Trophic shifting over a life cycle could explain the documented variation in results from field studies, but specific interactions of predators within food webs have been difficult to determine simply by comparing control and treatment assemblages in field experiments. We examined the trophic position of the Chinese praying mantid, Tenodera aridifolia sinensis (Saussure), using stable isotope analysis (SIA). We measured the δ(13)C and δ(15)N of field-collected arthropods, and of laboratory groups of mantids fed known diets of these arthropods chosen from the most abundant trophic guilds: herbivores (sap feeders and plant chewers), and carnivores. We also collected mantids from the field over a growing season and compared their SIA values to those of the laboratory groups. Both δ(13)C and δ(15)N of mantids fed carnivorous prey (spiders or other mantids) were higher than those fed herbivores (grasshoppers). SIA values from field-collected mantids were highly variable, and indicated that they did not take prey from trophic guilds in proportion to their abundances, i.e., were not frequency-dependent predators. Further, δ(15)N decreased from a high at egg hatch to a low at the third instar as early nymphs fed mainly on lower trophic levels, and increased steadily thereafter as they shifted to feeding on higher levels. We suggest that the community impact of generalist predators can be strongly influenced by ontogenetic shifts in diet.

Effects of irrigation system alterations on the trophic position of a threatened top predator in rice‐field ecosystems

“…For hemimetabolous insects with no pupal stage, isotopic shifts in newly emerged adults are inconsistent among taxa, (e.g. 15 N enrichment in Mantodea (Hurd, Dehart, Taylor, Campbell, & Shearer, ) and Collembola (Scheu & Folger, ) and 15 N depletion in Collembola (Haubert, Langel, Scheu, & Ruess, ). In newly emerged adult K. deyrolli (a hemimetabolous species), the physiological mechanisms of 15 N depletion remain unclear, but their trophic information may be carried over from the nymphal stage, as suggested by the fact that their trophic position was still higher in rice fields with a habitat corridor than in those with physical barriers.…”

“…For hemimetabolous insects with no pupal stage, isotopic shifts in newly emerged adults are inconsistent among taxa, (e.g. 15 N enrichment in Mantodea (Hurd, Dehart, Taylor, Campbell, & Shearer, 2015) and…”

Are specialists really safer than generalists for classical biocontrol?

“…The praying mantis T. sinensis, native to Asia, does not appear to have been intentionally introduced into North America. Rather, it may have arrived in egg sacs attached to nursery stock (Hurd et al 2015). Regardless, this mantis has been the subject of extensive study, including a series of manipulative field studies in the old-field early successional plant communities where they occur, that provide detailed insight into ecological effects in the invaded range (e.g., Hurd and Eisenberg1990;Hurd et al 2015).…”

“…Rather, it may have arrived in egg sacs attached to nursery stock (Hurd et al 2015). Regardless, this mantis has been the subject of extensive study, including a series of manipulative field studies in the old-field early successional plant communities where they occur, that provide detailed insight into ecological effects in the invaded range (e.g., Hurd and Eisenberg1990;Hurd et al 2015). This has revealed that, while the mantid appears to exert a bewildering number and diversity of direct and indirect effects on other community members, no single link appears to be particularly strong.…”

“…In contrast, the broadest generalists, by definition, feed on many different prey species and often across trophic levels (Polis et al 1989). This means that non-target impacts will be widespread, sometimes remarkably so (e.g., Hurd et al 2015;Hurd and Eisenberg 1990;Fig. 4).…”