How evolution created unlikely allies in a hidden world
Our earth is full of conflict and cooperation that we often don’t take into account. I’m talking about the interactions between plants and insects, groups that make up half of all terrestrial species. These organisms are linked by webs of deception, cooperation, and warfare, and learning how plants and insects interact will change your view of these hidden organisms forever.
The little old insect that lived in a plant
Arthur Weis, a professor of ecology and evolutionary biology at the U of T and a senior researcher at the Weis Lab, is studying how plants are responding to the pressures posed by the climate crisis. His lab also studies plant-insect interactions, ranging from cooperative to combative.
in a (n Article published in natural history, Weis described the relationship between goldenrod, a flower characterized by a riot of fluffy yellow spines, and the goldenrod gallfly, a 1.2 cm long fly found in the eastern and midwestern United States. After a female fly mates, she looks for suitable goldenrod plants to lay her eggs. Each time it finds a plant it finds satisfactory, the fly inserts the needle-like organ that extends from its rear end into the flower and ejects a single egg.
After the egg hatches, the larva burrows into the stem. By exposing the plant to chemicals in its saliva, “[the larva] causes a tumor on the goldenrod plant,” Weis said in an interview with The University. The larva then camps in the gall, chews on the tumor and is protected from parasitic wasps by a corky excursion until it emerges as an adult fly and spends the next two weeks before dying continuing the cycle.
Plants and their bodyguards
Plants are not passive victims – they also manipulate insects to protect themselves. According to Weis, tomato plants are often besieged by hungry caterpillars. “Tomatoes, when damaged, release a different class of volatile chemicals” that warn nearby parasitic wasps.
These parasitic wasps lay their eggs in the caterpillars and spell their downfall. Once the baby wasps hatch from the egg, they eat the caterpillar inside out and pop out as adult wasps.
However, tomato plants do not always depend on other insect species for defense. In a 2017 study published in natural ecology and evolution, the researchers prepared tomato plants for the attack and placed larvae on the plants. The authors found that the plants they prepared reduced the nutrient quality of their leaves, causing the larvae to feed on each other. The researchers reasoned that inducing cannibalism is a particularly sensible strategy — cannibalism not only reduces the number of herbivores, but also makes the remaining larvae less hungry and less likely to eat the plant.
But the caterpillars found ways to fight back. According to a 2021 article published in the New phytologistThe saliva of some caterpillars contains enzymes that prevent tomato plants from opening the pores in their leaves. This limits the plants’ ability to release wasp-attracting chemicals, effectively “silencing” the alarm.
Effects of the climate crisis
According to Weis, the ongoing climate crisis may change the way plants and insects interact by disrupting the overlap between the organisms’ life cycles. “For example, [if] The plant is very dependent on day length to regulate its growth cycle, but the insect is very dependent on temperature – well, day length doesn’t change, but temperature does [is],” he said. “There can end up being such discrepancies as to where the plant is at its best and most nutritious when the insect may not be ready to eat it.”
Elevated levels of carbon dioxide decrease the nutrient content of the leaves of certain plants, causing herbaceous insects to eat more. Additionally, recent studies suggest that exposure to high levels of carbon dioxide may limit plants’ ability to release some of the chemicals they use for self-defense. This leads me to one of the most compelling arguments for tackling the climate crisis – keeping our world sneaky and weird.
