Associate Professor Bret Elderd recently received over $2.1 million in grants from the US Department of Agriculture to study the effects of temperature on how hosts and parasites evolve together. The research makes use of the fall armyworm, a common crop pest, and a specialist virus that is lethal to the insect. Although the research is focused on the evolutionary dynamics of these particular species, Elderd hopes it will shed light on any broader trends of coevolution changes that are occurring due to increasing global temperatures.
The fall armyworm occurs mostly in warmer climates across North America, although in recent years it has been introduced to Africa and has done considerable damage to a variety of crops grown there. The parasite being studied is transmitted through leaf consumption, meaning transmission rate is proportional to how much and how often these insects feed. The virus propagates throughout the host’s hemolymph and ultimately kills it by breaking down the skin and splitting the insect open.
These particular subjects are ideal for observing evolutionary changes because of the short lifespans of the fall armyworm, which moves through a generation in around one month.
Elderd explained the basic inception for this type of research. “Rapid ecological change is associated with the warming climate. We see that in shifts in species ranges [of environments that they occupy], and we see it in species interactions. Previous research has shown transmission rates going up with higher temperatures.”
This research will examine evolutionary changes through two lenses. While adjusting temperatures, they will observe the rates at which the virus is transmitted to hosts. If the trend seen in previous research holds, transmission rate will up to a point increase with increasing temperatures.
On the micro-scale, they will look at changes in each species’ transcriptomes-the collective RNA molecules in cells which are used to code for genes. “We’re not looking at any individual genes in this dynamic. Our preliminary analysis has shown instead that there are sweeps of genes that operate in affected hosts, some of which are upregulated (genes are expressed more in response to stimuli) and some of which are downregulated,” Elderd explained.
It is unclear how many generations will need to be studied before evolutionary changes become apparent, but Elderd says the research will continue for about the next five years.
