Increased acclimation ability accompanies a thermal niche shift of a recent invasion

Abstract

Globalization is removing dispersal barriers for the establishment of invasive species and enabling their spread to novel climates. New thermal environments in the invaded range will be particularly challenging for ectotherms, as their metabolism directly depends on environmental temperature. However, we know little about the role climatic niche shifts play in the invasion process, and the underlining physiological mechanisms. We tested if a thermal niche shift accompanies an invasion, and if native and introduced populations differ in their ability to acclimate thermal limits. We used an alien ant species—Tapinoma magnum—which recently started to spread across Europe. Using occurrence data and accompanying climatic variables, we measured the amount of overlap between thermal niches in the native and invaded range. We then experimentally tested the acclimation ability in native and introduced populations by incubating T. magnum at 18, 25 and 30°C. We measured upper and lower critical thermal limits after 7 and 21 days. We found that T. magnum occupies a distinct thermal niche in its introduced range, which is on average 3.5°C colder than its native range. Critical thermal minimum did not differ between populations from the two ranges when colonies were maintained at 25 or 30°C, but did differ after colony acclimation at a lower temperature. We found twofold greater acclimation ability of introduced populations to lower temperatures, after prolonged incubation at 18°C. Increased acclimation ability of lower thermal limits could explain the expansion of the realized thermal niche in the invaded range, and likely contributed to the spread of this species to cooler climates. Such thermal plasticity could be an important, yet so far understudied, factor underlying the expansion of invasive insects into novel climates.

Evolution of cold tolerance and thermal plasticity in life history, behaviour and physiology during a poleward range expansion

“…Notably, the latter difference is associated with a better ability to survive cold winters in Swedish compared to French core populations (Arambourou & Stoks, 2015), suggesting the difference in chill coma recovery time to be biologically significant. Also, in other study systems, increases in cold tolerance associated with range expansion have been observed (Bujan et al, 2020;Butin et al, 2005;Kolbe et al, 2014;Medley et al, 2019). Related to this, latitudinal differences in cold resistance (higher in highlatitude regions) is a general pattern described in other insects (e.g.…”

Critical thermal limits in ants and their implications under climate change

“…We also emphasise the tremendous acclimation potential displayed by ant species, which may allow them to cope with future changes in temperature. Some studies have found that invasive species can exhibit large shifts in both CT min and CT max , for example in Wasmannia auropunctata (Coulin et al ., 2019) and Tapinoma magnum (Bujan et al ., 2021), which can translate into modifications in thermal niches that facilitate invasiveness. Other research has characterised the acclimation capacities of ants, as shown for two Aphaenogaster species in temperate forests in the USA (Warren & Chick, 2013).…”

Thermal tolerance regulates foraging behaviour of ants

“…The physiological traits that bracket such thermal performance curves are often defined as critical thermal limits and represent the range of temperatures at which an organism can be active. Critical thermal limits have been well‐explored in ectotherms with numerous studies focusing on diverse and abundant taxa such as ants (Baudier et al, 2018; Bishop et al, 2017; Braschler et al, 2020; Bujan et al, 2021; Garcia‐Robledo et al, 2018; Penick et al, 2017; Roeder, Bujan, et al, 2021). Questions linger through on how temperature affects different aspects of foraging and if activity is closely linked to an organism's thermal limits (Cerdá et al, 1998; Pereboom & Biesmeijer, 2003; Spicer et al, 2017; Welch et al, 2020).…”