Abundance of spring‐ and winter‐active arthropods declines with warming

Decline in diversity of tropical soil fauna under experimental warming

Climate change is exacerbating a global decline in biodiversity. Numerous observational studies link rising temperatures to declining biological abundance, richness and diversity in terrestrial ecosystems, yet few studies have considered the highly diverse and functionally significant communities of tropical forest soil and leaf litter fauna. Here, we report major declines in the order-level richness and diversity of soil and leaf litter fauna following three years of experimental whole-profile soil warming in a tropical forest. These declines were greatest during the dry season, suggesting that warming effects could be exacerbated by drought. Contrary to findings from higher latitudes, total faunal abundance increased under warming, and these effects were paralleled by major shifts in community composition. These responses were driven by increased dominance of a relatively small number of thermophilic taxa, and of oribatid mites in particular. Our study provides direct experimental evidence that warming causes diversity declines and compositional shifts for tropical forest soil and leaf litter fauna, a result with potential consequences for soil functions and biogeochemical cycles, and that highlights the vulnerability of tropical biodiversity to climate change.

Floral thermal biology in relation to pollen thermal performance in an early spring flowering plant

The floral microenvironment impacts gametophyte viability and plant-pollinator interactions. Plants employ mechanisms to modify floral temperature, including thermogenesis, absorption of solar radiation, and evaporative cooling. Whether floral thermoregulation impacts reproductive fitness, and how floral morphological variation mediates thermoregulatory capacity are poorly understood. We measured temperature of the floral microenvironment in the field and tested for thermogenesis in the lab in early spring flowering Hexastylis arifolia (Aristolochiaceae). We evaluated whether thermoregulatory capacity was associated with floral morphological variation. Finally, we experimentally determined the thermal optimum and tolerance of pollen to assess whether thermoregulation may ameliorate thermal stress to pollen. Pollen germination was optimal near 21 °C, with a 50% tolerance breadth of ~18 °C. In laboratory conditions, flowers exhibited thermogenesis of 1.5-4.8 °C for short intervals within a conserved timeframe (08:00-09:00 h). In the field, temperature inside the floral tube often deviated from ambient - floral interiors were up to 4 °C above ambient when it was cold, but some fell nearly 10 °C below ambient during peak heat. Flowers with smaller openings were cooler and more thermally stable than those with larger openings during peak heat. Thermoregulation maintained a floral microenvironment within the thermal tolerance breadth of pollen. Results suggest that H. arifolia flowers have a stronger capacity to cool than to warm, and that narrower floral openings create a distinct floral microenvironment, enhancing floral cooling effects. While deviation of floral temperature from ambient conditions maintains a suitable environment for pollen and suggests an adaptive role of thermoregulation, we discuss adaptive and nonadaptive mechanisms underlying floral warming and cooling.

Weather explains the decline and rise of insect biomass over 34 years

Insects have a pivotal role in ecosystem function, thus the decline of more than 75% in insect biomass in protected areas over recent decades in Central Europe1 and elsewhere2,3 has alarmed the public, pushed decision-makers4 and stimulated research on insect population trends. However, the drivers of this decline are still not well understood. Here, we reanalysed 27 years of insect biomass data from Hallmann et al.1, using sample-specific information on weather conditions during sampling and weather anomalies during the insect life cycle. This model explained variation in temporal decline in insect biomass, including an observed increase in biomass in recent years, solely on the basis of these weather variables. Our finding that terrestrial insect biomass is largely driven by complex weather conditions challenges previous assumptions that climate change is more critical in the tropics5,6 or that negative consequences in the temperate zone might only occur in the future7. Despite the recent observed increase in biomass, new combinations of unfavourable multi-annual weather conditions might be expected to further threaten insect populations under continuing climate change. Our findings also highlight the need for more climate change research on physiological mechanisms affected by annual weather conditions and anomalies.

Host-Parasitoid Phenology, Distribution, and Biological Control under Climate Change

Climate change raises a serious threat to global entomofauna-the foundation of many ecosystems-by threatening species preservation and the ecosystem services they provide. Already, changes in climate-warming-are causing (i) sharp phenological mismatches among host-parasitoid systems by reducing the window of host susceptibility, leading to early emergence of either the host or its associated parasitoid and affecting mismatched species' fitness and abundance; (ii) shifting arthropods' expansion range towards higher altitudes, and therefore migratory pest infestations are more likely; and (iii) reducing biological control effectiveness by natural enemies, leading to potential pest outbreaks. Here, we provided an overview of the warming consequences on biodiversity and functionality of agroecosystems, highlighting the vital role that phenology plays in ecology. Also, we discussed how phenological mismatches would affect biological control efficacy, since an accurate description of stage differentiation (metamorphosis) of a pest and its associated natural enemy is crucial in order to know the exact time of the host susceptibility/suitability or stage when the parasitoids are able to optimize their parasitization or performance. Campaigns regarding landscape structure/heterogeneity, reduction of pesticides, and modelling approaches are urgently needed in order to safeguard populations of natural enemies in a future warmer world.

Increasing temperatures reduce invertebrate abundance and slow decomposition

Decomposition is an essential ecosystem service driven by interacting biotic and abiotic factors. Increasing temperatures due to climate change can affect soil moisture, soil fauna, and subsequently, decomposition. Understanding how projected climate change scenarios will affect decomposition is of vital importance for predicting nutrient cycling and ecosystem health. In this study, we experimentally addressed the question of how the early stages of decomposition would vary along a gradient of projected climate change scenarios. Given the importance of biodiversity for ecosystem service provisioning, we measured the effect of invertebrate exclusion on red maple (Acer rubrum) leaf litter breakdown along a temperature gradient using litterbags in warming chambers over a period of five weeks. Leaf litter decomposed more slowly in the warmer chambers and in the litterbag treatment that minimized invertebrate access. Moreover, increasing air temperature reduced invertebrate abundance and richness, and altered the community composition, independent of exclusion treatment. Using structural equation models, we were able to disentangle the effects of average air temperature on leaf litter loss, finding a direct negative effect of warming on the early stages of decomposition, independent of invertebrate abundance. This result indicates that not only can climate change affect the invertebrate community, but may also directly influence how the remaining organisms interact with their environment and their effectiveness at provisioning ecosystem services. Overall, our study highlights the role of biodiversity in maintaining ecosystem services and contributes to our understanding of how climate change could disrupt nutrient cycling.

Duration of Low Temperature Exposure Affects Egg Hatching of the Colorado Potato Beetle and Emergence of Overwintering Adults

Simple Summary

The Colorado potato beetle is a pest of Solanaceae in China, more than 30 species of Solanaceae as host plants of the Colorado potato beetle, and this beetle can cause yield losses to potato farms. Temperature is one of the main factors that affect the growth and survival of insects. In recent years, due to global climate change, sudden drops in short-term temperatures are also frequent, which will affect insects. This paper studies the influence of short-term low temperature on the Colorado potato beetle. In laboratory experiments, we evaluated the effect of short-term low temperature on the Colorado potato beetle eggs, and the emerged date, the number of Colorado potato beetles, were analyzed in combination with the low temperature conditions. Our results show that low temperature had adverse effects on the development of Colorado potato beetle eggs and the emerged of adults Colorado potato beetles, and the longer the low temperature treatment time, the greater the impact.

Abstract

The Colorado potato beetle is a serious pest of Solanaceae in China. In early summer, cold spells in later spring may occur for brief periods in the field environmental conditions, and temperatures often deviate far below the normal temperature for short periods, such as sudden short-term low temperature, may affect the development of Colorado potato beetle eggs. This paper studies the effects of low temperature stress at 8 °C for 0 d, 1 d, 3 d, 5 d, 7 d, and 10 d on the development of Colorado potato beetle eggs. Our results show that egg survival is significantly affected by short-term low temperature exposure. The percentage of eggs hatched is significantly affected by different treatment times (p = 0.000)—the percentage of eggs hatched decreases with increased treatment time, and Colorado potato beetles will extend the wintering time of their soil to resist the effects of lower temperatures. Thus, exposure of Colorado potato beetles to a short-term low temperature affects their emergence and population growth; this study could provide information for the occurrence, monitoring, and early warning of Colorado potato beetle during short-term temperature.

The toughest animals of the Earth versus global warming: Effects of long-term experimental warming on tardigrade community structure of a temperate deciduous forest

Understanding how different taxa respond to global warming is essential for predicting future changes and elaborating strategies to buffer them. Tardigrades are well known for their ability to survive environmental stressors, such as drying and freezing, by undergoing cryptobiosis and rapidly recovering their metabolic function after stressors cease. Determining the extent to which animals that undergo cryptobiosis are affected by environmental warming will help to understand the real magnitude climate change will have on these organisms. Here, we report on the responses of tardigrades within a five-year-long, field-based artificial warming experiment, which consisted of 12 open-top chambers heated to simulate the projected effects of global warming (ranging from 0 to 5.5°C above ambient temperature) in a temperate deciduous forest of North Carolina (USA). To elucidate the effects of warming on the tardigrade community inhabiting the soil litter, three community diversity indices (abundance, species richness, and Shannon diversity) and the abundance of the three most abundant species (Diphascon pingue, Adropion scoticum, and Mesobiotus sp.) were determined. Their relationships with air temperature, soil moisture, and the interaction between air temperature and soil moisture were tested using Bayesian generalized linear mixed models. Despite observed negative effects of warming on other ground invertebrates in previous studies at this site, long-term warming did not affect the abundance, richness, or diversity of tardigrades in this experiment. These results are in line with previous experimental studies, indicating that tardigrades may not be directly affected by ongoing global warming, possibly due to their thermotolerance and cryptobiotic abilities to avoid negative effects of stressful temperatures, and the buffering effect on temperature of the soil litter substrate.