Spring colonies of the ant Temnothorax nylanderi tolerate cadmium better than winter colonies, in both a city and a forest habitat

Abstract

A recent study showed that, in the ant Temnothorax nylanderi, city colonies are more tolerant to cadmium than forest colonies. However, because of annual variation in biological factors (e.g. body size, anti-stress protein production or trace metal accumulation rate), trace metal tolerance may vary over the year. We aimed at testing whether tolerance to cadmium of colonies of T. nylanderi differs between two different seasons within the same year (winter and spring). We also assessed whether the better cadmium tolerance of city colonies was constant over these two different time points. We collected colonies at the end of their hibernation period (winter colonies) and several weeks after (spring colonies) from two different habitats (forest and city) to assess whether response to cadmium was consistent regardless of the environment. We exposed colonies to a cadmium or a control treatment for 61 days. We compared tolerance to cadmium between spring/winter and city/forest colonies by measuring several life history traits. We found that spring colonies tolerates cadmium better than winter colonies, and that city colonies have a higher tolerance to cadmium but only in spring. Although further studies with replicated pairs of city/forest habitats and different years will be necessary to confirm those results, our study suggests that tolerance to trace metals can fluctuate along the yearly cycle.

Keep your cool: Overwintering physiology in response to urbanization in the acorn ant, Temnothorax curvispinosus

“…For logistical ease and to reduce acclimation to the testing environment we induced chill coma (loss of motor activity due to impaired neuromuscular function; Denlinger & Jr, 2010) at -10 °C on whole colonies of workers and then observed individuals for the time of recovery, determined by antennae or leg movement. The chill coma temperature was selected based on similar tests of CCRT in congenerics (Jacquier et al, 2022;Modlmeier et al, 2012), related woodland ants (Leptothorax spp. Heinze et al, 1996;Heinze et al, 1998), and freeze susceptible insects in general (Turnock & Fields, 2005).…”