Recent research news from the Ecological Society of America

December 4, 2024
For Immediate Release

Contact: Mayda Nathan, gro.asenull@adyam

The Ecological Society of America (ESA) presents a roundup of four research articles recently published across its esteemed journals. Widely recognized for fostering innovation and advancing ecological knowledge, ESA’s journals consistently feature illuminating and impactful studies. This compilation of papers explores the influence of changing rainfall on invasive grasses in North American rangelands, the effect of heat waves on a major potato pest, the substitution of one group of predators for another in salt marshes and the impacts of small native mammals and large introduced ungulates on Chihuahuan Desert grasslands.

From Ecological Applications:

Rugged invasive winter annuals reveal their sensitive side
Author contact: Matthew J. Rinella (vog.adsunull@allenir.ttam)

Non-native winter annual plants in the western U.S. like cheatgrass, which sprout in the fall and die off by summer, can be surprisingly sensitive to seasonal changes in precipitation, suggests a new study. Models built from 31 years of monitoring data on cheatgrass and a sister species, Japanese brome, reveal that a mere 6.5 mm increase in average rainfall in autumn (a strong possibility under future climate conditions) has the potential to drive a 40% rise in the amount of these grasses. Moreover, the analysis indicates that multiple years of drier spring conditions also stimulate brome production, challenging the findings of previous studies carried out over shorter periods of a year or less. The results point to the importance of long-term data for understanding the spread of non-native plants, and the future threat posed by these species.

Read the article: Integrating experiments and monitoring reveals extreme sensitivity of invasive winter annuals to precipitation

From Ecosphere:

A recent Ecosphere study finds that Colorado potato beetles (a major crop pest) are more vulnerable to heat waves that strike early in the beetles’ development.
Image credit: Scott Bauer, USDA | CC BY 2.0

Potato pest can’t take the heat (wave)
Author contact: William C. Wetzel (ude.anatnomnull@leztew.mailliw)

Heat waves can harm both crops and the pests that eat them, making it hard to predict how farm yields will fare as climate change makes heat waves more frequent and intense. Digging into the details, a new study shows that impacts of heat waves on Colorado potato beetle, a major pest of potato crops, vary with beetle developmental stage and crop strain. Simulating heat wave conditions in the field at different points in time on both pest-resistant and vulnerable potato varieties, researchers found that the beetles thrived on vulnerable crops no matter when temperatures rose. On pest-resistant crops, however, higher temperatures early in the beetles’ life cycle caused the survivors to grow larger faster but ultimately have lower survival once they reached the adult stage. Notably, only these early heat waves had any effect; heat that struck later in the beetles’ life cycle had little impact, whether on resistant or vulnerable potato plants. Ultimately, though, heat wave timing was unrelated to crop yields, showing how focusing solely on pest responses to climate can paint a misleading picture. To make accurate predictions about crops, pests and yields under climate change, the study authors argue for consideration of heat wave timing in pest management strategies and expanded planting of pest-resistant strains. 

Read the article: Heat wave impacts on crop–pest dynamics are dependent upon insect ontogeny and plant resistance

From Ecology:

When top predators are away, the mesopredators will play
Author contact: Joseph P. Morton (ude.lfunull@notrom.j)

Salt marshes of the U.S. Southeast may seem like simple ecosystems because they are dominated by a single species of plant (smooth cordgrass), but new research shows appearances can be deceptive. Short-term studies of select marsh organisms have suggested that top predators like fish, turtles and large crabs promote cordgrass growth by keeping grazing snails and crabs in check. To explore whether these relationships hold up over longer time spans and across the full marsh community, a research team built mesh-fenced plots in a Georgia salt marsh, excluding the largest aquatic marsh predators for three years. Initially, the absence of large predators triggered a proliferation of herbivorous snails, as expected. By the third year of the experiment, however, snail numbers began to decline as another organism surged: mud crabs. Known as “mesopredators,” or predators that can themselves fall prey to bigger animals, mud crabs took advantage of the top predator-free zones to feast in peace on snails. As a result, the amount of cordgrass remained essentially unchanged in the absence of top predators, as the mesopredatory mud crabs took over the job of keeping grazers in check. The mud crabs’ move to top dog status suggests that salt marshes may be more resilient to the loss of larger predators than previously thought. The findings also highlight the importance of longer-term studies for untangling food web relationships, even in seemingly simple settings. 

Read the article: Mesopredator release moderates trophic control of plant biomass in a Georgia salt marsh

A new study in Ecology used fenced exclosures like this one to show that, over 25 years, small herbivores like rodents and rabbits had a greater impact on Chihuahuan Desert vegetation than cattle and other non-native ungulates.
Image credit: Kieran Andreoni, from Andreoni et al., 2024

It’s the little ones that make the difference in Chihuahuan grasslands
Author contact: Robert L. Schooley (ude.sionillinull@yeloohcs)

Encroaching shrubs have transformed the dry grasslands of North America’s Chihuahuan Desert, but a 25-year experiment suggests that the traditional villains of grassland degradation — cattle and other introduced large grazers — have surprisingly little influence on ongoing grassland loss. Established in 1995, the experiment used a variety of fencing materials to block different groups of mammals (non-native cattle and oryx, as well as native rabbits, hares and rodents) from large desert plots, letting researchers examine how herbivores affected the plant community over time. Unexpectedly, after 25 years cattle and oryx had almost no impact on the amount of grass or mesquite shrub cover, which could be a result of these animals’ low density. On the other hand, native mammals had noteworthy impacts on the dryland plants. Rodents reduced plant diversity and created a distinct mix of vegetation, while rabbits and hares suppressed grass cover during wetter periods. Overall, the results suggest that climate was the major driving force of vegetation change over the course of the study, with small native mammals playing a role in certain conditions while herbivory in general neither helped nor hindered the steady expansion of shrubs.

Read the article: Effects of multiple mammalian herbivores and climate on grassland–shrubland transitions in the Chihuahuan Desert

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The Ecological Society of America, founded in 1915, is the world’s largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 8,000 member Society publishes six journals and a membership bulletin and broadly shares ecological information through policy, media outreach and education initiatives. Visit the ESA website at https://www.esa.org

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