Critical thermal limits in ants and their implications under climate change

Abstract

Critical thermal limits (CTLs) constrain the performance of organisms, shaping their abundance, current distributions, and future distributions. Consequently, CTLs may also determine the quality of ecosystem services as well as organismal and ecosystem vulnerability to climate change. As some of the most ubiquitous animals in terrestrial ecosystems, ants are important members of ecological communities. In recent years, an increasing body of research has explored ant physiological thermal limits. However, these CTL data tend to centre on a few species and biogeographical regions. To encourage an expansion of perspectives, we herein review the factors that determine ant CTLs and examine their effects on present and future species distributions and ecosystem processes. Special emphasis is placed on the implications of CTLs for safeguarding ant diversity and ant-mediated ecosystem services in the future. First, we compile, quantify, and categorise studies on ant CTLs based on study taxon, biogeographical region, methodology, and study question. Second, we use this comprehensive database to analyse the abiotic and biotic factors shaping ant CTLs. Our results highlight how CTLs may affect future distribution patterns and ecological performance in ants. Additionally, we identify the greatest remaining gaps in knowledge and create a research roadmap to promote rapid advances in this field of study.

Carbohydrate‐rich diet increases critical thermal maximum in ants

“…Our results support the idea that CT max could be a good predictor of ant activity in semiarid tropical regions. Other studies found that CT max was more strongly associated with microclimatic than macroclimatic gradients (Baudier et al, 2018; Nascimento et al, 2022). This result could explain why CT max is tightly linked to local ant activity.…”

“…The CT max is particularly important in the lives of poikilothermic ectotherms (Sinclair et al, 2016; Bennet et al, 2021), whose body temperatures depend exclusively on environmental temperatures. Furthermore, CT max can determine species distribution and abundance at regional and local scales (Deutsch et al, 2008; Kearney & Porter, 2009; Clusella‐Trullas et al, 2011; Buckley et al, 2012; Arnan & Blüthgen, 2015; Sunday et al, 2019), and, ultimately, their responses to disturbance and climate change (Roeder et al, 2021a; Nascimento et al, 2022). Finally, because CT max also affects species performance, activity, and behaviour, it may also impact the outcome of ant‐plant mutualisms (Fitzpatrick et al, 2014; Tamashiro et al, 2019).…”

“…Second, CT max is highly variable among ant species, populations, and even nestmates (Villalta et al, 2020; Roeder et al, 2021b; Nascimento et al, 2022). Whereas many abiotic and biotic factors may explain this variability, much of it remains unexplained (Nascimento et al, 2022). Finally, carbohydrates are an important nutritional component in the diets of many ant species because greater carbohydrate availability boosts colony activity, worker survival, and food resource defence (Hölldobler & Wilson, 1990; Blüthgen & Fiedler, 2004; McGlynn & Parra, 2016).…”

“…First, they are very sensitive to environmental changes and rapidly respond to shifts in both environmental conditions and resource availability (Arnan et al, 2012; Andersen, 2019). Second, CT max is highly variable among ant species, populations, and even nestmates (Villalta et al, 2020; Roeder et al, 2021b; Nascimento et al, 2022). Whereas many abiotic and biotic factors may explain this variability, much of it remains unexplained (Nascimento et al, 2022).…”

Neotropical stingless bees display a strong response in cold tolerance with changes in elevation

“…For example, changes in critical thermal limits have been associated with variations in some aspects of climate, such as precipitation and temperature, which determine species' distribution at both geographic and temporal gradients (e.g. Sunday et al, 2011;Kellermann et al, 2012;García-Robledo et al, 2018;Nascimento et al, 2022). Given that critical thermal limits are good predictors of an organism's potential response to extreme temperature changes, they are commonly used in calculating thermal sensitivity indices, which estimates a population or species' susceptibility to climate change (Deutsch et al, 2008;Sunday et al, 2014;Clusella-Trullas et al, 2021;Roeder et al, 2021a).…”