![]() For long-lived insects like ants that can be active throughout the year, lipid content should fluctuate in response to varying temperature, resource availability, and other phenological events like the production of winged reproductives ( Ricks and Vinson 1972, Hahn 2006, Cook et al. However, resources that contribute toward maintaining high lipid levels are not always available year-round. To survive high and low temperatures, insects must often mobilize energy stores, such as lipids, to fuel cellular responses. 2001, Arrese and Soulages 2010, Sinclair and Marshall 2018). Fat bodies are metabolically active tissues that are important for storing and releasing energy in response to demand ( Canavoso et al. One physiological trait that could track seasonal changes in temperature is lipid content. Despite the importance of phenology for insects, we still lack vital information on if and how certain physiological traits covary with temperature across time. Insects, which are mostly ectotherms, are particularly susceptible to fluctuating temperatures though as their body temperature tracks their environment ( Calosi et al. During these seasonal shifts in environmental conditions, individuals often undergo physiological changes that help buffer against the extremes. ![]() Temperature, as one abiotic example, can be highly variable across time periods, spanning more than 30☌ daily and over 100☌ seasonally ( New et al. While intraspecific variation in physiological traits often follows seasonal patterns, our results suggest fluctuations in temperature may account for a portion of the variance observed in traits like lipid content.Įvery year organisms encounter a range of abiotic conditions that accompany important life events like development, emergence, hibernation, migration, and reproduction ( Chown and Nicolson 2004, Hahn and Denlinger 2007, Lease and Wolf 2011). Temperature again had a significant impact such that after 10 days, lipid content of ants in the hottest chamber (30☌) had decreased by more than 75%. We next assessed if lipid levels from a group of ants collected at a single time point could change by placing individuals into environmental chambers set at 10, 20, and 30☌ (i.e., the approximate span of average temperatures from March to November). In doing so, we found that lipid content of ants declined almost 70% from cool months (November lipid content = 14.6%) to hot months (August lipid content = 4.6%). We first assessed if lipid content was highest during cooler temperatures when ants were less active and less metabolically stressed. From March to November, we extracted lipids from surface workers of 14 colonies while simultaneously recording ground temperature. We focus on lipid content as fat bodies are metabolically active tissues that are important for storing and releasing energy in response to demand, which could be vital for survival under variable temperatures. Here, we test predictions on how one trait-lipid content-covaries with temperature using a conspicuous, ground-dwelling harvester ant. Yet, we often lack information on how certain physiological traits covary with temperature across time. ![]() Temperature is one of the most important environmental conditions affecting physiological processes in ectothermic organisms like ants.
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