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As global insect populations face alarming declines, often referred to as an “insect apocalypse,” researchers are keen to understand how these creatures are adapting to climate change, and to forecast which species may thrive or struggle in the future.
A recent analysis focused on Colorado grasshoppers reveals that while the situation is complex, scientists possess critical insights needed for making informed predictions about these insects and their responses to environmental shifts.
The research, published on January 30 in the journal PLOS Biology, stemmed from the unexpected discovery of a collection of 13,000 grasshoppers gathered from a single mountain site in Colorado between 1958 and 1960 by entomologist Gordon Alexander from the University of Colorado Boulder (CU Boulder). Following his tragic death in a plane accident in 1973, the collection was saved by Alexander’s son and eventually donated to the CU Museum. However, it remained underutilized until 2005, when César Nufio, a postdoctoral fellow, reexamined and curated the specimens, initiating further surveys to gather additional grasshopper samples from the same locations.
The research team—comprising Nufio, Caroline Williams from the University of California, Berkeley, Lauren Buckley of the University of Washington, and postdoctoral researcher Monica Sheffer—analyzed the effects of climate change on the body sizes of six grasshopper species over the past 65 years. With their cold-blooded physiology, these insects have been shown to exhibit heightened sensitivity to temperature variations.
While there has been speculation regarding a potential decrease in size among animal populations as a means of coping with increased heat, the study found that certain grasshopper species have actually increased in size over the decades. This phenomenon can be attributed to these species taking advantage of an earlier onset of spring, which allows them to consume larger quantities of vegetation. This growth advantage was predominantly seen in species that undergo nymphal diapause, a juvenile overwintering stage, enabling them to start feeding earlier in the season. In contrast, species that hatch from eggs laid in the fall—termed egg diapausers—did not experience this benefit and showed a decline in size, likely due to earlier drying of available vegetation.
“This research highlights that climate impact will inevitably produce both winners and losers among species, but within those species, population segments can exhibit varying responses based on their ecological conditions,” Sheffer noted.
Based on their understanding of the grasshoppers’ life cycles and the environmental conditions of their habitat, the researchers were able to make several predictions about the potential responses of these species to climate change.
“We compiled existing knowledge about the environment, including elevation gradients, and how different grasshopper species might respond, which was informed by extensive research into their natural history. While not all our predictions held true, many were confirmed,” explained Williams, who holds the John L. and Margaret B. Gompertz Chair in Integrative Biology at UC Berkeley.
“Determining which species are likely to succeed or fail due to climate change remains an ongoing challenge,” Buckley added. “We hope this study helps clarify underlying principles that can lead to more accurate predictions and appropriate responses to the ecological changes driven by climate shifts.”
Historical Grasshopper Collection
The historical grasshopper collection was meticulously compiled by Gordon Alexander during three summers of fieldwork. He not only collected and preserved the specimens but also documented the timing of six distinct life stages of the grasshoppers. Following his death, the neatly arranged specimens remained untouched until Nufio uncovered their significance in 2005, paving the way for comparative analyses with present-day grasshoppers.
Collections like this have proven vital for extensive research into climate change impacts. One notable example includes a study of various vertebrate species—mammals, birds, reptiles, and amphibians—conducted from 1904 to 1940 by Joseph Grinnell at UC Berkeley. The recent resurvey of similar ecological sites a century later has provided valuable insights into the ecological consequences of climate change on California’s wildlife.
Eventually, Nufio and his team accumulated approximately 17,000 new grasshopper specimens from comparable locations around Boulder. The paper detailing changes in grasshopper size from 1960 to 2015 marks a significant contribution to this field of study, as the authors integrated previous laboratory studies and experimental observations to better understand the patterns they identified.
The grasshoppers examined belong to the Acrididae family, more commonly recognized as short-horned grasshoppers. The majority are categorized as general grazers, while some specialize in specific grass types. Within the studied group, two species—Eritettix simplex and Xanthippus corallipes—are classified as nymphal diapausers, reaching maturity as early as May; while another two—Aeropedellus clavatus and Melanoplus boulderensis—emerge from eggs laid earlier in the year, maturing by mid-June; and a final pair—Camnula pellucida and Melanoplus sanguinipes—are late-season egg diapausers, maturing by late July.
The analysis indicated that nymphal diapausers experienced growth at lower elevations, around 6,000 feet, whereas the early and late season egg diapausers demonstrated a size reduction over the decades at these same elevations.
“For those species that emerge in late summer, when conditions are harsh with high temperatures and low moisture, we observed the most significant negative impacts of climate change,” Williams commented.
Interestingly, none of the grasshopper species exhibited size increases at higher elevations—up to approximately 13,000 feet—even in light of more substantial warming trends documented in these regions. This lack of size growth may be linked to late snow cover, which delays the availability of food sources during the early growing season. These findings align with previous experiments conducted by the team, which assessed grasshopper adaptability to variations in temperature and moisture at different elevations.
“The results suggest a dichotomy where grasshoppers may thrive and grow larger as a response to warming, or conversely, experience stress leading to a decrease in size,” Buckley reflected.
Buckley noted that similar patterns have been observed in research on butterflies, indicating a shared ecological narrative. “We see encouraging similarities in retention of fundamental biological principles that could enhance our predictive capacities regarding climate change responses,” she added.
The research team plans to continued their collaboration to delve deeper into the metabolic, biochemical, and genetic alterations linked to the observed size changes in grasshoppers.
“Utilizing these museum collections gave us the unique ability to compare historical data from the same sites—ensuring no significant changes in land use occurred during this 60-year warming period—applying a consistent methodology,” said Williams. “These significant historical specimens have allowed us to track environmental changes over time.”
Other contributors to the study include Julia Smith from the University of Washington, Simran Bawa from UC Berkeley, and Ebony Taylor, Michael Troutman, and Sean Schoville from the University of Wisconsin, Madison. This research received support from the National Science Foundation (DEB-1951356, DEB-1951588, DEB-1951364).
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