Behavioral thermoregulation in a small herbivore avoids direct UVB damage

Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

Terrestrial organisms and ecosystems are being exposed to new and rapidly changing combinations of solar UV radiation and other environmental factors because of ongoing changes in stratospheric ozone and climate. In this Quadrennial Assessment, we examine the interactive effects of changes in stratospheric ozone, UV radiation and climate on terrestrial ecosystems and biogeochemical cycles in the context of the Montreal Protocol. We specifically assess effects on terrestrial organisms, agriculture and food supply, biodiversity, ecosystem services and feedbacks to the climate system. Emphasis is placed on the role of extreme climate events in altering the exposure to UV radiation of organisms and ecosystems and the potential effects on biodiversity. We also address the responses of plants to increased temporal variability in solar UV radiation, the interactive effects of UV radiation and other climate change factors (e.g. drought, temperature) on crops, and the role of UV radiation in driving the breakdown of organic matter from dead plant material (i.e. litter) and biocides (pesticides and herbicides). Our assessment indicates that UV radiation and climate interact in various ways to affect the structure and function of terrestrial ecosystems, and that by protecting the ozone layer, the Montreal Protocol continues to play a vital role in maintaining healthy, diverse ecosystems on land that sustain life on Earth. Furthermore, the Montreal Protocol and its Kigali Amendment are mitigating some of the negative environmental consequences of climate change by limiting the emissions of greenhouse gases and protecting the carbon sequestration potential of vegetation and the terrestrial carbon pool.

Ultraviolet-B radiation in relation to agriculture in the context of climate change: a review

Over the past few decades, the amount of ultraviolet-B radiation (UV-B) reaching the earth's surface has been altered due to climate change and stratospheric ozone dynamics. This narrow but highly biologically active spectrum of light (280-320 nm) can affect plant growth and development. Depletion of ozone and climate change are interlinked in a very complicated manner, i.e., significantly contributing to each other. The interaction of climate change, ozone depletion, and changes in UV-B radiation negatively affects the growth, development, and yield of plants. Furthermore, this interaction will become more complex in the coming years. The ozone layer reduction is paving a path for UV-B radiation to impact the surface of the earth and interfere with the plant's normal life by negatively affecting the plant's morphology and physiology. The nature and degree of the future response of the agricultural ecosystem to the decreasing or increasing UV-B radiation in the background of climate change and ozone dynamics are still unclear. In this regard, this review aims to elucidate the effects of enhanced UV-B radiation reaching the earth's surface due to the depletion of the ozone layer on plants' physiology and the performance of major cereals.

Photoprotective egg pigmentation reduces negative carryover effects of ultraviolet radiation on stink bug nymph survival

Solar ultraviolet radiation (UV) can have a wide range of negative effects on animal fitness that take place not only during, but also after exposure (carryover effects). UV-induced carryover effects and potential adaptations to avoid or mitigate them are understudied in terrestrial animals, including arthropods and their potentially most vulnerable life stages. The spined soldier bug, Podisus maculiventris, increases the emergence of its eggs that are exposed to UV radiation by coating them in sunscreen-like pigmentation, but consequences of these conditions of embryonic development for nymphs and adults are unknown. We measured stink bug nymph survival, adult size and sex ratio following exposure of differently pigmented eggs across a range of UV intensities. Nymph survival to adulthood decreased with higher intensity of embryonic UV exposure and this carryover effect decreased with higher level of egg pigmentation, similar to previously observed effects on embryonic survival. Nymph development time, adult size and sex ratio were not affected by embryonic exposure to UV radiation nor by photoprotective egg pigmentation. This study is the first to demonstrate the potential for lethal carryover effects of UV radiation in terrestrial insects, highlighting the need for more studies of how this pervasive environmental stressor can affect fitness across life stages.

Flexible habitat choice by aphids exposed to multiple cues reflecting present and future benefits

Mothers choose suitable habitats for laying offspring to maximize fitness. Because habitat quality varies in space and time, mothers gather information to choose among available habitats through multiple cues reflecting different aspects of habitat quality at present and in the future. However, it is unclear how females assess and integrate different cues associated with current rewards and future safety to optimize oviposition/larviposition decisions, especially across small spatial scales. Here, we tested the individual and interactive effects of leaf surface, leaf orientation, and leaf bending direction on larviposition site choice and fitness benefits of wheat aphids (Metopolophium dirhodum) within individual leaves. We found that females preferred upper over lower surfaces for gaining current food-related rewards, downward- over upward-facing surfaces for avoiding potential abiotic risks, and sunken over protruding surfaces for avoiding potential biotic risks. When facing conflicting cues during larviposition, females preferred downward-facing/sunken surfaces over upper surfaces, suggesting that females prioritize potential safety at the cost of current rewards during decision making. Most importantly, our combined-cue experiments showed females still assessed secondary cues (i.e., the upper surface) when first-ranked cues (i.e., the downward-facing/sunken surface) are available, even though females only gained relatively small fitness rewards through secondary cues, and females can integrate different cues associated with current rewards and potential safety in a multiplicative way to make flexible and complex larviposition decisions. Overall, our findings provide new insights into how animals collect and process multi-cue information associated with current rewards and potential safety to maximize fitness at small spatial scales.

Dose-Response and Temperature Dependence of the Mortality of Spider Mite and Predatory Mite Eggs Caused by Daily Nighttime Ultraviolet-B Irradiation

The two-spotted spider mite, Tetranychus urticae, is an economically important agricultural pest. A novel physical control method involving daily nighttime UV-B irradiation was recently developed for use in strawberry greenhouses. However, the overlapping of leaves after March prevents direct irradiation to T. urticae on the lower leaf surface, decreasing control effect. Excessive UV-B irradiation causes leaf sunscald in winter. Therefore, optimization of UV-B irradiance and a compensatory control agent are desired. Temperature may affect the survival of organisms exposed to UV-B, although the temperature dependence of UV-B damage is controversial. A phytoseiid mite, Neoseiulus californicus, is a prominent predator but vulnerable to a single UV-B irradiation. We compared dose-response and temperature dependence of UV-B damage between T. urticae and N. californicus eggs under daily nighttime UV-B irradiation. Unexpectedly, N. californicus showed greater resistance to UV-B than T. urticae, and the mortality was increased and decreased at low and high temperatures, respectively. This makes possible the application of UV-B doses that are lethal for spider mites but safe for phytoseiid mites. Overall, we concluded that combined use of phytoseiid mites with UV-B lamps is advantageous to spider mite management in strawberry greenhouses.