Climate Change: Resetting Plant-Insect Interactions

Abstract

Elevated CO 2 and temperature are altering the interactions between plants and insects with important implications for food security and natural ecosystems. Ecologically, the acceleration of plant phenology by warming is generating mismatches between plants and insect pollinators. Similarly, shifting the rate of plant development relative to insect development can amplify or minimize the consequences of herbivory. Warming also enables some insects to increase the number of generations per year, thus increasing damage to plant communities. The suitability of plant tissues as food for insects also is modulated by global change. Elevated CO 2 typically increases the concentration of leaf carbohydrates and in combination with elevated temperature decreases nitrogen (N) content. Together, these changes lower nutritional value, causing certain herbivores to consume more foliage to meet their nutritional needs. Whereas the responses of primary metabolites in plants to global change are reasonably well understood, how elevated CO 2 and temperature affect plant defensive compounds (allelochemicals) is considerably less predictable. Recent studies indicate that exposure to elevated CO 2 suppresses the plant defense hormone jasmonic acid (JA) while stimulating production of salicylic acid (SA). By differentially affecting defense compounds, these changes in plant hormones potentially increase susceptibility to chewing insects and enhance resistance to pathogens. Exposure to elevated temperature, in contrast, stimulates JA, ethylene (ET), and SA, enhancing defenses. A deeper understanding of how elevated CO 2 and temperature, singly and in combination, modulate plant hormones promises to increase our understanding of how these elements of global change will affect the positive and negative interactions between plants and insects.Chemoautotrophs notwithstanding, plants provide energy in the form of carbohydrates for all nonphotosynthetic organisms, including insects. Not long after the colonization of land by plants 510 million years ago, plants and insects have engaged in an evolutionary arms race that continues today-plants evolve mechanisms to minimize consumption by insects, and insects evolve mechanisms to circumvent these defenses. Rapid changes in Earth's atmosphere initiated by the human use of fossil fuels is resetting this complex coevolutionary relationship, not only between plants and herbivores but also between plants and their mutualistic partners, including pollinators. Insects have the potential to cause enormous reductions in crop yields and the productivity of natural ecosystems, as well as to provide irreplaceable pollination services that underpin much of the world's agriculture.The combustion of fossil fuels during the Industrial Revolution initiated a rapid rise in atmospheric CO 2 concentration that is accelerating today; preindustrial levels were approximately 280 mL L 21 and below 300 mL L 21 for the previous 20 million years (Pearson and Palmer, 2000). Today's atmosphere is approximately 397 mL L 21...

Relation between O3-Inhibition of Photosynthesis and Ethylene in Paddy Rice Grown under Different CO2Concentrations

“…These results suggest that elevated CO 2 may reduce the levels or function of ethylene and thereby ameliorate the O 3 -inhibition of photosynthesis. Kobayakawa and Imai (2013c) found that JA contents in rice leaves were decreased slightly by elevated CO 2 , as reported previously (DeLucia et al, 2012). Likewise, rice plants grown under elevated CO 2 are more susceptible to leaf blast than those grown under ambient CO 2 (Kobayashi et al, 2006).…”

“…However, the amelioration of O 3 -inhibition by SA application and the increase of endogenous SA in rice leaves (Kobayakawa and Imai, 2012b) are less than in other plants such as Arabidopsis (Sharme et al, 1996), tobacco (Yalpani et al, 1994) and soybean (Zhao et al, 2010). Moreover, elevated CO 2 induces SA production and suppresses JA production in leaves such as tomato, soybean, and ginger (DeLucia et al, 2012). In paddy rice, Kobayakawa and Imai (2013c) found that endogenous JA and MeJA contents in leaves were decreased slightly by elevated CO 2 (800 cm 3 m -3 ).…”

Changes in the background losses of woody plant foliage to insects during the past 60 years: are the predictions fulfilled?

“…Consequently, the relationships between plants and insects are among the most intensively studied biotic interactions [3,4], and the exploration of changes in insect-plant relationships caused by the abiotic drivers of global change has become increasingly popular during the past decades. The existing scenarios generally predict that increasing temperature will cause faster increases in herbivory than in plant productivity [5][6][7], although the suggested mechanisms behind this prediction are diverse. Population densities of plant-feeding insects were predicted to increase because of direct beneficial effects of warmer climate on insect herbivores [8] and adverse effects of increased climatic variability on their natural enemies [9].…”

Geographical pattern in first bloom variability and its relation to temperature sensitivity in the USA and China

“…The phenological change relating to the start and end of the growing season can affect the vegetation productivity and carbon cycle (Keenan et al 2014;Richardson et al 2010Richardson et al , 2013. Also, the shift in plant phenophases would result in mismatches between plants and pollinators, predators and prey, and pests and hosts (DeLucia et al 2012;Donnelly et al 2011;Hegland et al 2008). In addition, human health is affected by plant phenology, through the linkage between flowering phenology and allergenic pollen (Reid and Gamble 2009).…”