Jamie Weir wins prestigious Linnean Society Medal

Jamie’s work considers a fundamental question facing modern ecology: how resilient is wildlife to a warming climate?

His PhD project focused on the tree/caterpillar/bird food chain that occurs throughout temperate woodlands during spring, and is widely suspected of being vulnerable to increasing temperatures. 

The results revealed that caterpillars are surprisingly resilient and have a range of strategies that allow them to adapt to changing springtime conditions, such as the ability to feed on different trees.

This not only maximises their chances of survival but reduces the likelihood of negative impacts on other species higher in the woodland food chain that rely on them.

The findings highlight the importance of identifying which ecosystems and species have similar adaptive strategies, and which are most vulnerable to climate change and need greater protection. 

Climate change can affect the timing of stages in the life cycles of many different species. 

In particular, warmer spring conditions can advance many of the natural events we associate with the changing season: trees coming into leaf, plants flowering, or birds migrating.

This could potentially disrupt finely timed food chains, as some animals and plants rely on occurring at the same time as other species—such as a predator with a seasonal food source.  

The extent of these changes can vary across different species, and some are responding more strongly to the warmer conditions than others, increasing the likelihood of mistiming.  

He reared thousands of caterpillars in captivity to experimentally test the effects of hatching at the wrong time on their survival, growth, and development. 

Surprisingly, he found evidence suggesting caterpillars adopt a range of ingenious ‘buffering’ mechanisms to help them cope with the unpredictability of their spring environment. 

These strategies may also make them resilient to some of the disruptive impacts of increasing temperatures.

These buffering strategies include ‘bet-hedging’, where there is substantial variation in the hatching time of caterpillars within a single clutch of eggs. 

This means that even if some individuals hatch at the wrong time, at least some of their siblings are likely to hatch at the correct time.  

Caterpillar species common in spring typically have a very broad diet, and can consume leaves from a wide range of different plant species, all of which open their leaves at different times.

Because different plant species are affected by higher temperatures in different ways, even if a caterpillar hatches at the wrong time relative to one species, an alternative will likely be available to feed on.

Not only that, caterpillars that hatch too early, before leaves have appeared on plants and trees, can sometimes survive for weeks without food, or burrow into leaf buds to feed on the developing tissue. 

Jamie’s work revealed that the effects of hatching late varied across different plant species, and that hatching late on some plants has surprisingly little effect on caterpillars survival or growth.

The historical focus in previous studies on oak trees as a key food plant seems to have given a misleading impression of how vulnerable these caterpillars are.

The results suggest that ecologists should re-examine other ecosystems that are also assumed to be vulnerable to mistiming, and identify how widespread similar buffering mechanisms may be.

Given the concerns about the effects of climate change, identifying which species and food chains are most threatened—and which are most resilient— is vital so that conservation efforts are directed where there is the greatest need. 

All of the Linnean medals and awards will be officially presented at the Society’s anniversary meeting on 22 May 2025.

Other 2025 awardees include a game changing botanical illustrator and an impassioned promoter and researcher of UK hedgerows and the wildlife they support.

Jamie Weir 

Announcing the Linnean Society's Medal and Award Recipients 2025