Ant species exhibit high physiological tolerance to cold temperatures
the verdict
SUPPORTED
the evidence backs this
refutedsupported
the weight of evidence
7 sources for · 0 against
Peer-reviewed literature examining ant thermal tolerances confirms that multiple ant species exhibit measurable physiological adaptations and cold tolerance across various habitats and climatic conditions.
Environmental temperature can alter body size and thermal tolerance, yet the effects of temperature rise on the size-tolerance relationship remain unclear. Terrestrial ectotherms with larger body sizes typically exhibit greater tolerance of high (and low) temperatures. However, while warming tends to increase tolerance of high temperatures through phenotypic plasticity and evolutionary change, warming tends to decrease body size through these mechanisms and thus might indirectly contribute to worse tolerance of high temperatures. These contrasting effects of warming on body size, thermal tolerance, and their relationship are increasingly important in light of global climate change. Here, we used replicated urban heat islands to explore the size-tolerance relationship in response to warming. We performed a common garden experiment with a small acorn-dwelling ant species collected from urban and rural populations across three different cities and reared under five laboratory rearing temperatures from 21 to 29 °C. We found that acorn ant body size was remarkably insensitive to laboratory rearing temperature (ant workers exhibited no phenotypic plasticity in body size across rearing temperature) and among populations experiencing cooler rural versus warmer urban environmental temperatures (no evolved differences in body size between urban and rural populations). Further, this insensitivity of body size to temperature was highly consistent across each of the three cities we examined. Because body size was robust to temperature variation, previously described plastic and evolved shifts in heat (and cold) tolerance in acorn ant responses to urbanization were shown to be independent of shifts in body size. Indeed, genetic (colony-level) correlations between heat and cold tolerance traits and body size revealed no significant association between size and tolerance. Our results show how typical trait correlations, such as between size and thermal tolerance, might be decoupled as populations respond to contemporary environmental change.
Urban areas experience higher temperatures compared to rural areas and as such, are increasingly considered places of acclimatization and adaptation to warming. Small ectotherms, such as insects, whose body temperature rises with habitat temperature, are directly affected by temperature changes. Thus, warming could have a profound effect on insect behavior and physiology. To test if the urban heat island effect drives higher thermal tolerance and activity changes, we used globally distributed and abundant insects-ants. We measured the heat and cold tolerance of 14 ant species distributed across urban and peri-urban areas. As thermal traits are often correlated with ant foraging, we measured foraging activity during three consecutive years across eight sites. Contrary to our prediction, ants exposed to the urban heat island effect did not have a higher heat tolerance than peri-urban ants. Instead, cold tolerance varied across habitats, with ants from the cooler, peri-urban habitats being able to tolerate lower temperatures. We recorded the same pattern of invariant heat and higher cold tolerance for ants in the canopy, compared to ground nesting ants. Ant activity was almost 10 times higher in urban sites and best predicted by cold, not heat tolerance. These unexpected results suggest that we need to rethink predictions about urban heat islands increasing insect heat tolerance in urban habitats, as cold tolerance might be a more plastic or adaptable trait, particularly in the temperate zone.
Habitat fragmentation is a major cause of biodiversity loss. Fragmentation can alter thermal conditions on the remaining patches, especially at habitat edges, but few studies have examined variations in thermal tolerance of species in fragmented habitats. Ants are sensitive to both habitat fragmentation and temperature changes, and are an ideal taxon for studying these impacts. Here, we focused on the dimorphic ant species <i>Pheidole nodus</i> in a fragmented habitat island system (Thousand island lake) in China. We assessed critical thermal maximum (CTmax), minimum (CTmin), and range (CTrange) temperatures for both minor (workers) and major workers (soldiers) of 2307 individuals from 117 edge and interior colonies across 9 islands during relatively hot and cold seasons. Using mixed-effect linear models, we explored the effects of island area, habitat type (edge vs. interior), season, and caste (worker vs. soldier) on CTmax, CTmin, and CTrange. We found temperatures were 1-3 °C higher in edge than interior sites in relatively hot season. Yet, only CTmax and CTrange in edge populations were higher than those of interior sites on smaller islands. CTmax was higher in relatively hot season and CTmin was lower in relatively cold season, indicating seasonal plasticity in thermal tolerance. Workers consistently had higher CTmax and lower CTmin than soldiers. These findings underscore the importance of seasonality, worker caste, and interactive effect between island area and habitat type in shaping thermal tolerance of a dominant dimorphic ant species on fragmented habitat islands. Our study provides a roadmap for integrating thermal biology into studies of how fragmentation impacts biodiversity.<h4>Supplementary information</h4>The online version contains supplementary material available at 10.1007/s42995-025-00288-8.
Species may exhibit similar traits via different mechanisms: environmental filtering and local adaptation (geography) and shared evolutionary history (phylogeny) can each contribute to the resemblance of traits among species. Parsing trait variation into geographic and phylogenetic sources is important, as each suggests different constraints on trait evolution. Here, we explore how phylogenetic distance, geographic distance, and geographic variation in climate shape physiological tolerance of high and low temperatures using a global dataset of ant thermal tolerances. We found generally strong roles for evolutionary history and geographic variation in temperature, but essentially no detectable effects of spatial proximity per se on either upper or lower thermal tolerance. When we compared the relative importance of the factors shaping upper and lower tolerances, we found a much stronger role for evolutionary history in shaping upper versus lower tolerance, and a moderately weaker role for geographic variation in temperature in shaping upper tolerance when compared with lower tolerance. Our results demonstrate how geographic variation in climate and evolutionary history may have differential effects on the upper and lower endpoints of physiological tolerance. This Janus effect, where the relative contributions of geographic variation in climate and evolutionary history are reversed for lower versus upper physiological tolerances, has gained some support in the literature, and o
The red imported fire ant (Solenopsis invicta) is a non-native invasive species that rapidly spread northward in the United States after its introduction from South America in the 1930s. Researchers predicted that the northward spread of this invasive ant would be limited by cold temperatures with increased latitude and greater elevation in the Blue Ridge Escarpment region of the United States. The presence of S. invicta at relatively high elevations north of their projected limits suggests greater cold tolerance than previously predicted; however, these populations might be ephemeral indicati
The thermal limits of individual animals were originally proposed as a link between animal physiology and thermal ecology. Although this link is valid in theory, the evaluation of physiological tolerances involves some problems that are the focus of this study. One rationale was that heating rates shall influence upper critical limits, so that ecological thermal limits need to consider experimental heating rates. In addition, if thermal limits are not surpassed in experiments, subsequent tests of the same individual should yield similar results or produce evidence of hardening. Finally, severa
worker ants alive at temperatures close to 46 °C. Studies of related ant species in similar urban habitats showed that prolonged exposure to city heat-island
Tetramorium immigrans—also known as the immigrant pavement ant, pavement ant, and the sugar ant in parts of North America—is an ant native to Europe, which also occurs as an introduced pest in North America. Its common name comes from the fact that colonies in North America usually make their nests under pavement. This is one of the most commonly seen ants in North America, being well adapted to u
Te…
Everything we examined (7)
This check searched the claim as stated. It did not run a separate search for evidence against it.