Tritrophic metabolism of plant chemical defenses and its effects on herbivore and predator performance

Insect herbivores are frequently reported to metabolize plant defense compounds, but the physiological and ecological consequences are not fully understood. It has rarely been studied whether such metabolism is genuinely beneficial to the insect, and whether there are any effects on higher trophic levels. Here, we manipulated the detoxification of plant defenses in the herbivorous pest diamondback moth (Plutella xylostella) to evaluate changes in fitness, and additionally examined the effects on a predatory lacewing (Chrysoperla carnea). Silencing glucosinolate sulfatase genes resulted in the systemic accumulation of toxic isothiocyanates in P. xylostella larvae, impairing larval development and adult reproduction. The predatory lacewing C. carnea, however, efficiently degraded ingested isothiocyanates via a general conjugation pathway, with no negative effects on survival, reproduction, or even prey preference. These results illustrate how plant defenses and their detoxification strongly influence herbivore fitness but might only subtly affect a third trophic level.

TROPHODYNAMICS OF MARINE ORGANISMS IN THE EPIPELAGIC LAYER OF THE OKHOTSK SEA IN 2000S

New data on matter and energy transfer between major components of the Okhotsk Sea ecosystem are obtained on the base of trophodynamic modeling, taking into consideration their production and food consumption rates. The main trophodynamic relationships in the pelagic and bottom communities are determined from observations on zooplankton and nekton abundance, organic carbon content, food habits of marine organisms, and their isotope composition in 2000–2014. The total zooplankton production in the entire Okhotsk Sea in these years is assessed as 2616 . 106 t in raw weight, including 2275 . 106 t for non-predatory plankton, and 341 . 106 t for predatory plankton. So high total production of zooplankton is conditioned by favorable environmental conditions and dominance of high-productive species. Taking into account the rate of zooplankton consumption by predators, only 22.4 % of the total annual zooplankton production was consumed annually, with 16.2 % grazed by predatory plankton and 6.2 % by nekton. In carbon units, 831.0 . 106 tC was produced annually in the Okhotsk Sea at the first trophic level, 177.4 . 106 tC at the second trophic level, 18.1 . 106 tC at the third trophic level, 0.74 . 106 tC at the fourth trophic level, and 0.016 . 106 tC at the fifth trophic level. Pelagic nekton consumed 159 . 106 tC annually. The nekton prey included 85.5 % of zooplankton, 12.8 % of nekton, and 1.7 % of zoobenthos, by biomass. The main part of zooplankton consumed by nekton (50.7 %) was grazed by walleye pollock, 18.9 % by herring, 16.6 % by squids, 7.6 % by capelin, 5.3 % by deep-sea smelt, and 0.9 % by salmons. The total annual production of organisms in the epipelagic layer of the Okhotsk Sea exceeded 109 tons of C (1027.4 . 106 tC/year equal to the biomass of 17.85 . 109 t in wet weight). Primary production is estimated as 67.60 % of gross production in carbon units, microheterotrophic organisms produce 13.30 %, dominant zooplankton groups — 18.60 % (copepods 11.40 %, euphausiids 5.50 %, sagittas 1.20 %, and hyperiids 0.50 %), the portion of nekton production is estimated as 0.13 % of gross production.

Evolving in the Community

This chapter examines how species in simple community modules evolve in order to adapt to one another. It first considers the ecological basis of natural selection before discussing the three general types of traits that underlie the trophic interactions between predators and their prey. It then explores how the type of traits involved in species interactions affect the dynamics of adaptation and describes the underlying dynamics of adaptation when all the species in a simple community module can coevolve, along with the influences of various system features on the outcome of this coevolution. The chapter focuses on the simultaneous dynamics of abundances and traits that result from species interactions by looking at the case involving one resource and one consumer, with only trait being ecologically important for each species, and how this simple consumer-resource system evolves when a third trophic level is added to the system.

Biologia de Imaturos e Adultos de Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) Alimentados com Lagartas de Dione juno juno (Cramer) (Lepidoptera: Nymphalidae), criadas em Diferentes Genótipos de Maracujazeiro

Resumo. Estudou-se o efeito da alimentação com lagartas de Dione juno juno (Cramer) (Lepidoptera: Nymphalidae), criadas em diferentes genótipos de maracujazeiro: Passiflora edulis Sims., Passiflora edulis f. flavicarpa Deg. (Seleção de Jaboticabal), P. edulis f. flavicarpa (cv. Sul Brasil) e P. edulis f. flavicarpa (cv. Maguary FB-100), Passiflora alata Dryand, Passiflora serrato-digitata Linn. e Passiflora foetida Linn. sobre imaturos e adultos de Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae). O experimento foi conduzido sob condições controladas (temperatura: 26 ± 1°C, UR de 60 ± 10% e fotofase de 14 horas). Grupos de cinco ninfas de P. nigrispinus de 2º ínstar foram mantidos em recipientes plásticos (4,5 cm de altura e 7,5 cm de diâmetro), contendo as presas no seu interior. Diariamente, cinco lagartas de D. juno juno de 10 dias de idade (cerca de 2,0 cm de comprimento), criadas em folhas dos diferentes genótipos de maracujazeiro foram oferecidas aos predadores. O experimento constou de 10 repetições, totalizando 50 ninfas por tratamento. Foram avaliadas, diariamente, as durações e sobrevivência de cada instar; peso de ninfas (24 horas após a ecdise) e de adultos. Os resultados mostram a influência de genótipos de maracujazeiro sobre o terceiro nível trófico, onde lagartas criadas no genótipo P. edulis f. flavicarpa Sel. Jaboticabal mostraram-se mais adequadas ao desenvolvimento do predador. Os resultados obtidos nesse trabalho mostram a influência de genótipos de maracujazeiro sobre o terceiro nível trófico. O genótipo P. edulis f. flavicarpa cv. Sul Brasil mostra-se menos adequado ao predador, sugerindo de forma negativa a associação entre a resistência de plantas e o uso do controle biológico. Já os genótipos P. edulis e P. edulis f. flavicarpa Seleção de Jaboticabal podem ser utilizados juntamente com o predador, pois essas cultivares não afetaram o terceiro nível trófico. P. edulis f. flavicarpa cv. Maguary FB-100, considerado pouco adequado ao desenvolvimento de lagartas de D. juno juno, afetou o predador, resultando em associação negativa entre esse genótipo e o controle biológico.Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) Fed with Dione juno juno (Cramer) (Lepidoptera: Nymphalidae) Caterpillars, Raised in Different Passion fruit Genotypes, Adults and Immatures BiologyAbstract. The development of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) nymphs fed with Dione juno juno (Cramer) (Lepidoptera: Nymphalidae) larvae reared on leaves of the passion fruit genotypes Passiflora edulis Sims., Passiflora edulis f. flavicarpa Deg. (Seleção de Jaboticabal), P. edulis f. flavicarpa (cv. Sul Brasil) and P. edulis f. flavicarpa (cv. Maguary FB-100), P. alata, P. serrato-digitata and P. foetida. The experiment was conducted under controlled conditions (temperature: 26 ± 1°C, RH = 60 ± 10% and photophase of 14 hours). Second instar nymphs of the predator were kept in plastic cups (4.5 cm high and 7.5 cm wide) groups of five. Ten-day-old (approx. 2 cm) D. juno juno larvae reared on leaves of different passion fruit genotypes were provided daily to P. nigrispinus. The experiment was carried out with 10 replications, totalizing 50 nymphs per treatment. Daily evaluations were performed to measure the duration and viability of each instar, the body mass of nymphs (24 hours after each ecdysis) and adults, and the duration and viability of the nymph phase and adult longevity under starvation. Results show the influence of passion fruit genotypes at the third trophic level, since larvae reared with P. edulis f. flavicarpa (Seleção de Jaboticabal) have shown to be more adequate for predator development. The results of this experiment show the influence of passion fruit genotypes on the third trophic level. The genotype P. edulis f. flavicarpa cv. Sul Brasil has a less appropriate to the predator, suggesting a negative way the association between host plant resistance and use of biological control. Already P. edulis and genotypes P. edulis f. flavicarpa Jaboticabal Selection can be used along with the predator because these cultivars did not affect the third trophic level. P. edulis f. flavicarpa cv. Maguary FB-100, considered ill-suited to the development of larvae of D. juno juno, affected the predator, resulting in a negative association between this genotype and biological control.

Essential Oils as “A Cry for Help”. A Review

This work is an update of a recently published review and is consistently referred to this article and recent findings about plants’ indirect defense are added on. Herbivore induced plant volatiles (HIPVs) and their effects on the third trophic level that involves predators and parasitoids are discussed. The fact that plants are not passive individuals is confirmed on the basis of several studies. Plants can perceive and respond to cues in their environments with plastic morphological, physiological and behavioral traits. Plasticity allows plants to tailor their defenses to their current and expected risks caused by herbivores. The “cry for help” of plants is also observed from the carnivores’ point of view. The volatile mixture contains crucial information for decisions of carnivorous insects. Furthermore, the most important methods to examine the behavioral response of carnivorous insects to HIPVs are presented not only in laboratory set ups but also in the field. Manipulations of plants by silencing genes or over-expressing genes can help to understand mechanisms of indirect defense. Various interesting examples of indirect defense reveal the possibility to use HIPVs in biological control. Therefore, the application of synthetic pesticides, that pollute the environment, may be reduced in the future.