According to climate models,
global temperatures are anticipated to increase by 2-4 degrees Celsius
by the end of this century (approximately 4-7°F). Cold-blooded animals, or
ectothermic species
, are particularly sensitive to environmental fluctuations, as they depend on ambient temperatures for thermoregulation. In tropical ecosystems, where temperatures remain stable year-round, these cold-blooded organisms might experience limited thermal variability. Consequently, they could exhibit lower resilience to temperature shifts, heightening their susceptibility to heat stress.
Social insects, including ants and bees, exemplify cold-blooded species that adapt their behavior in response to temperature changes at both individual and colony levels, complicating predictions about their responses to climate change. For instance, arboreal ants frequently engage in “service exchanges” with host plants through
mutualistic relationships
. These intricate ant-plant interactions extend their impact, influencing other species. A notable example is certain bird species that prefer nesting in acacia trees defended by ants. Disruptions to this mutualism due to rising temperatures could trigger significant ecological ramifications.
To investigate how increasing temperatures influence symbiotic relationships, researchers analyzed the impacts of direct sunlight and experimentally elevated temperatures on tropical ants residing in trees. This study, conducted in Panama’s Metropolitano Natural Park from February to April 2024, focused on a specific ant species that engages in a mutually beneficial relationship with giant acacia plants. These ants provide protection against herbivores and eliminate competing vegetation in exchange for nourishment and shelter.
The researchers set up open-topped plastic enclosures around 33 acacia trees, ensuring that each ant colony was evenly distributed between shaded and sunlit areas. Sixteen control enclosures were well-ventilated through plastic holes, while seventeen heated enclosures were sealed at the base and contained black paper to enhance heat absorption. The temperature within the heated enclosures was approximately 1.3°C (2.3°F) higher than the control enclosures.
After a week, the researchers assessed ant activity on the branches twice daily—once in the morning (from 7 a.m. to 9:30 a.m.) and again in the afternoon (from 12 p.m. to 3:30 p.m.). Each branch was marked, and researchers counted the number of ants crossing it within a three-minute span, simultaneously recording branch and spine temperatures and noting their sun or shade exposure. They found that ant colonies in heated environments exhibited reduced activity compared to control colonies, particularly on sun-exposed leaves in the afternoon. The ants tended to navigate through the spines, avoiding direct surfaces. Although the spines were approximately 2°C (3.6°F) warmer than the branches, they provided shelter from direct sunlight, indicating that the ants adjusted their behavior to manage heat.
To determine the effect of elevated temperatures on ant defense mechanisms, the researchers pinned a pincer leaf to the acacia trunk’s base and monitored interactions. Findings revealed that ant colonies in heated enclosures demonstrated diminished defensive behavior toward foreign foliage compared to control colonies.
Researchers then measured the maximum temperature threshold, labeled Tmax, which indicates the temperature above which ants can no longer function. They collected three worker ants from each colony prior to, and three weeks following, enclosure setup. Each ant was placed in a tube at 36°C (97°F), with the temperature increased by 2°C (3.6°F) every 10 minutes. Researchers tapped the tubes gently to assess ant recovery capabilities, recording the temperature threshold for maximum function.
The average Tmax for the 33 ant colonies was 46.5°C (115.7°F), showing no significant difference between control and heated groups. Similar Tmax values (around 48°C or 118°F) were noted for the same ant species from hotter, drier environments, suggesting these ants possess a naturally limited tolerance for high temperatures. The branch temperatures in their experiments reached 48°C (118°F), indicating that ants are already operating close to their thermal threshold.
The research team concluded that ants reduced their activity levels in response to heat, consequently weakening their protective role for the acacia plants. The researchers speculated that such behavioral changes may render the plants more vulnerable to herbivores and disrupt interactions with other species, including pathogens and birds. They emphasized the need for future studies examining how climate stressors affect these complex interdependencies and their broader ecological implications.
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Source: sciworthy.com
