Thermal biology of the alien ground beetle Merizodus soledadinus introduced to the Kerguelen Islands

Abstract

Thermal tolerance is one of the major determinants of successful establishment and spread of invasive aliens. Merizodus soledadinus (Coleoptera, Carabidae) was accidentally introduced to Kerguelen from the Falkland Islands in 1913. On Kerguelen, the climate is cooler than the Falklands Islands but has been getting warmer since the 1990s, in synchrony with the rapid expansion of M. soledadinus. We aimed to investigate the thermal sensitivity in adults of M. soledadinus and hypothesised that climate warming has assisted the colonisation process of M. soledadinus. We examined (1) survival of constant low temperatures and at fluctuating thermal regimes, (2) the critical thermal limits (CTmin and CTmax) of acclimated individuals (4, 8 and 16°C), (3) the metabolic rates of acclimated adults at temperatures from 0 to 16°C. The FTRs moderately increased the duration of survival compared to constant cold exposure. M. soledadinus exhibited an activity window ranged from -5.5 ± 0.3 to 38 ± 0.5°C. The Q10 after acclimation to temperatures ranging from 0 to 16°C was 2.49. Our work shows that this species is only moderately cold tolerant with little thermal plasticity. The CTmin of M. soledadinus are close to the low temperatures experienced in winter on Kerguelen Islands, but the CTmax are well above summer conditions, suggesting that this species has abundant scope to deal with current climate change.