The response of ants to climate change

Abstract

Ants (Hymenoptera: Formicidae) are one of the most dominant terrestrial organisms worldwide. They are hugely abundant, both in terms of sheer numbers and biomass, on every continent except Antarctica and are deeply embedded within a diversity of ecological networks and processes. Ants are also eusocial and colonial organisms—their lifecycle is built on the labor of sterile worker ants who support a small number of reproductive individuals. Given the climatic changes that our planet faces, we need to understand how various important taxonomic groups will respond; this includes the ants. In this review, we synthesize the available literature to tackle this question. The answer is complicated. The ant literature has focused on temperature, and we broadly understand the ways in which thermal changes may affect ant colonies, populations, and communities. In general, we expect that species living in the Tropics, and in thermally variable microhabitats, such as the canopy and leaf litter environments, will be negatively impacted by rising temperatures. Species living in the temperate zones and those able to thermally buffer their nests in the soil or behaviorally avoid higher temperatures, however, are likely to be unaffected or may even benefit from a changed climate. How ants will respond to changes to other abiotic drivers associated with climate change is largely unknown, as is the detail on how altered ant populations and communities will ramify through their wider ecological networks. We discuss how eusociality may allow ants to adapt to, or tolerate, climate change in ways that solitary organisms cannot and we identify key geographic and phylogenetic hotspots of climate vulnerability and resistance. We finish by emphasizing the key research questions that we need to address moving forward so that we may fully appreciate how this critical insect group will respond to the ongoing climate crisis.

Weather impacts on interactions between nesting birds, nest-dwelling ectoparasites and ants

“…As blowfly numbers were lower in nests containing ants, compared to nests without ants, the presence of the predatory insects might improve nest sanitation, particularly in warm weather when foraging ant workers could be more active 37 , 38 . Although ant predation on blowflies has not been directly observed in this study, predatory ants removing other ectoparasites from bird nests has been previously documented 36 .…”

“…For example, ants can act as predators and reduce the number of nest-dwelling ectoparasites, such as bugs Oeciacus vicarius (Heteroptera: Cimicidae) or flies Carnus hemapterus (Diptera: Carnidae) 35 , 36 . As the foraging activity of ant workers can be promoted by warm weather 37 , 38 , the sanitation of bird nests by ants might be more effective at higher ambient temperatures, potentially having subsequent fitness consequences for the host birds.…”

“…We repeated these tests for the late nestling period, when chicks were older and the blowfly larvae would be developing within bird nests 14 . Additionally, we checked whether reduced occurrence or intensity of ectoparasite infestation was associated with the presence of ants at a range of ambient conditions, when the foraging activity of ant workers may vary 37 , 38 . We also explored the fitness consequences for birds, expressed as the variation in the growth (feather length and body mass) in relation to weather, blowfly parasitism, or ant presence within the nests.…”

Climate and ant richness explain the global distribution of ant-plant mutualisms

“…Temperature and precipitation may directly influence the ability of plants to produce sugary nectar, which attracts ants to establish mutualistic interactions (34). Likewise, ants are thermally sensitive and activity of ants against herbivores can be temperature-dependent (24, 35), leading to indirect effects via ants on the diversity of plants with domatia and EFNs. These may partly explain the low presence of ant-defended plants in temperate regions.…”

“…Surprisingly, elevation range was a poor predictor of domatium- and EFN-bearing plant richness, possibly because temperature exerts a stronger influence on ant-defended plants and ant distributions. Likewise, precipitation seasonality has only minor negative effects on ant-associated plant richness indirectly via ant guild richness, indicating a potential risk of desiccation for ants in regions with high rainfall seasonality (35). Past climate change is generally influential on plants and ants (39, 40), however, we find a negligible importance on ant-associated plants.…”