When we think of global warming, we tend to be a bit selfish and think of how it affects us in our daily lives, but the warming temperatures on our planet have the potential to affect the base of all of our food webs, plants (Image Credit: Matt Lavin, CC BY-SA 2.0).

Phenology in a warming world: differences between native and non-native plant species (2019) Zettlemoyer et al., Ecology Letters, https://dx.doi.org/10.1111/ele.13290

The Crux

The timing of life-history events (such as births, growing seasons, or reproductive period) is called “phenology”, and this aspect of an organism’s life is particularly sensitive to climate change. So much so that changes in the phenology of certain processes are often used as an indicator of climate change and how it affects a given organism.

We’ve talked about the effects of rising temperatures in animals here on Ecology for the Masses, but there is a lot of evidence in the scientific literature for climate change causing a multitude of different changes in the phenology of various plants. Not only does the direction of the change differ (some organisms experience delays in certain events, others have earlier starts), but the size, or magnitude, of the change also differs. The authors of today’s study wanted to examine these changes in the context of an invasive plant species and how it may be able to outcompete a native plant.

What They Did

The authors simulated a climate change induced temperature increase to investigate what effect the increase had on the flowering and fruiting phenology of native and non-native plants. Any difference in the phenologies would tell them that a warming climate was driving these differences. Using this experimental setup, the authors asked four questions:

1. Does the phenology of native and non-native plants differ, and is warming causing this difference?
2. If these phenologies differ, do the two different plant types differ in how their phenology changes?
3. Are the phenologies of native and non-native plants synchronous at the population level?
4. Are the flowering times and ability of a non-native plant species to change that time dependent on the temperature correlated with how successful they are at invading new habitats?

Did You Know:  Cascading Effects of Phenology

When the phenology of an organism changes, this can result in cascading effects throughout the food web. Normally, British birds returning the the U.K. for spring feed their chicks with caterpillars, which live on oak trees and feed on the leaves. Warming temperatures have pushed the growth of oak leaves earlier in the spring, meaning that the caterpillars that feed on them tend to peak in number earlier in the spring, as well. But, the birds that eat the caterpillars are not able to lay their eggs earlier because they don’t spend their winters in the U.K. and can’t modify their egg-laying with the change in season, and as a result the chicks don’t get as much food.

What They Found

Non-native plant species flowered and fruited earlier than the native species, and warm temperatures only increased these differences. Native species did not exhibit any change in the phenology of fruiting and flowering under the warmer temperatures. Non-native species also flowered more synchronously than native species, and earlier flowering in the non-native plants was associated with a wider geographic spread. However, the amount that a plant (native or non-native) could change its phenology was not associated with wider geographic spread.

Problems?

In science, it is best to get as much data as possible in order to get an accurate representation of what is happening. The authors of today’s paper did not include Canada in their data on geographic spread, and thus the range limits of both native and non-native species were artificially truncated. Limitations such as these are a part of science, but the authors took care to mention them and how they may have affected the results.

So What?

Non-native plants responded to warmer temperatures by flowering and fruiting earlier than their native counterparts, and they were flowering and fruiting earlier than native plants to begin with. These earlier phenologies, combined with the findings that these earlier dates for these events are correlated with a wider geographic spread, mean that as our planet continues to warm, some invasive non-native plants may eventually outcompete and wipe out all native plants in some areas.

This may not seem like such a big deal, as these results are saying that some plants will still be able to succeed and grow in these areas. What one has to consider, though, is the fact that these plants are not native to these environments. A lot of invasive species tend to be generalist, hence their ability to succeed in new places. But when a habitat loses part of its native population, other species that depend on that specific organism are likely to go extinct, as well.

For more information of the effects of climate change on plant life, check out our interview with Annie Schmitt here.