Chemical Ecology of Plant Parasitoids affected by climate change and pollution

Windy temperatures, precipitation levels, and the intensity and length of sunlight have all been shown to influence the chemical ecology of plant parasitoids. Plant parasitoids, according to research, have introduced chemical compounds as an important way of interacting with their hosts in a specific ecosystem. Furthermore, certain toxins, such as ozone, have been shown to have an impact on the nature and quantities of these plant secretions, which include aldehydes, aliphatic alcohols, benzenoids, and terpenoids. Therefore, climate change and pollution have an effect on life species involved in a parasitoid ecology because it affects plants secretions that attract some species of parasitoids and repel some of them, which consequently reduces the numbers of parasitoids that can be supported by various host plants in a given ecosystem.

Effects of Climate Change and Pollution

An ecological system with parasitoid organism contains plants and host insects, among others. It is important to note that, parasitoid organisms spend most of their life time attached to their hosts, hence, anything that would have significant effect on the hosts would also affect significantly. Often, climate change and pollutants have an effect on the secretions of the plants and thus affects the way in which plants attract or repel some specific plant parasitoids.

Global warming has been found to increase the amount of secretions that plant release to the atmosphere while reduction in temperatures result in a reduction in the volatile organic compounds that plants release to the atmosphere. Therefore, increase in temperature increases the communication between host plants and their respective parasitoids in an ecosystem while decrease in temperature reduces the communication between plants and other plants and even the insect species (Hance et al., 2007). For instance, on a sunny day, there is a higher likelihood that some plants – such as flowers – would secrete favorable substances that would make the parasitoids quite comfortable, thus, attracting a lot most of them. This is the same reason why plants attract more insects, both hosts and parasitoids, in warmer conditions (Wajnberg and Collaza, 2013). However, the temperatures should not rise beyond levels that would be detrimental to the physiological functions of the plant. Beyond this point, plants release less volatile organic compounds – such as acetone and methanol - into the atmosphere and, thus, attract less parasitoid species. In addition to atmospheric changes, gas pollutants have also been found to affect the interaction between plants and insects. Research indicates that, plants may release the volatile organic compounds (VOCs) as a defensive measure that is aimed at keeping the parasitoids away from (Vivaldo, Masi, Taiti, Caldarelli & Mancuso, 2017). In such a scenario, it is evident that the plant that is emitting the VOCs would not be a host to any of the parasitoids within the ecosystem during that period.

It has also been noted that gases in the atmosphere also affect the communication between plants and insect species, the number of hosts and parasitoids that a plant will host varies with the amount of pollutants in the atmosphere. These atmospheric pollutants affect these volatile emissions at two levels; the reactions that lead to these emissions and by reacting with the volatile emissions producing new compounds. According to Pinto et al (2010), ozone pollution causes oxidative stress in plants thus causing a change in the chemical composition of volatile emissions. As a result, there will be a reduction in the number of plant species that are attracted to a plant through specific emissions. Consequently, any plant parasitoids that are being hosted by such plants would be adversely affected, which might even lead to their deaths, hence, reducing the number of the parasitoids in the respective ecosystem.

In addition to affecting the physiological reactions in a plant, atmospheric pollutants have also been found to affect the composition of volatile plant emissions in the atmosphere. According to Blande, Holopainen, and Niinemets (2014), hydroxyl radicals, oxides of nitrogen, and ozone change the chemical composition of volatile plant emissions. Consequently, it may have two effects on the communication between the species in an ecosystem. First, it may lead to some of the parasitoids failure to identify their host plants, thus, leading to their deaths. As noted earlier, plant parasitoids are adversely affected by the emission of the volatile organic compounds, which makes a given habitat to be unfavorable to them. Therefore, such parasitoids will perish and become extinct within the given ecosystem. Secondly, the new chemical composition of the volatile emissions can be perceived by some of the plant parasitoids as informative signals. As a result, these parasitoids will be drawn towards plants that have the secretions that favor their growth and development.

Conclusion

Climate changes affect the communication between host plants and the plant parasitoids because of the changes in the amounts of volatile emissions released to the atmosphere. Global warming causes more secretion while reduction of the temperature reduces the amount of secretions to the atmosphere. Also, atmospheric gas pollutants also affect the communication between different species. As a result, climate change and air pollution adversely affects the number of plant parasitoids that may be drawn to a respective host plant. In addition, it has been noted that the emission of volatile organic compounds draws the plant parasitoids away from some host plants. Therefore, it would be rational to point out that climate changes have the potential of decreasing the number of plant parasitoids in a given ecosystem and even making some types of parasitoids to become extinct in a given ecosystem.

References

Blande, J. D., Holopainen, J. K., Niinemets, Ü. (2014). Plant volatiles in polluted atmospheres: stress responses and signal degradation. Plant, cell & environment, 37(8), 1892-1904.

Boullis, A., Francis, F., Verheggen, F. J. (2015). Climate change and tritrophic interactions: Will modifications to greenhouse gas emissions increase the vulnerability of herbivorous insects to natural enemies? Environmental entomology, 44(2), 277-286.

Hance, T., Van Baaren, J., Vernon, P., Boivin, G. (2007). Impact of extreme temperatures on parasitoids in a climate change perspective. Annual review of entomology, 52.

Pinto, D. M., Blande, J. D., Souza, S. R., Nerg, A. M., Holopainen, J. K. (2010). Plant volatile organic compounds (VOCs) in ozone (O3) polluted atmospheres: the ecological effects. Journal of chemical ecology, 36(1), 22-34.

Vivaldo, G., Masi, E., Taiti, C., Caldarelli, G., & Mancuso, S. (2017). The network of plants volatile organic compounds. Scientific Reports, 7(1), 11050.

Wajnberg, E., Colazza, S. (2013). Chemical ecology of insect parasitoids. John Wiley & Sons.