Desiccation and temperature resistance of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae): pedestals for invasion success?

Abstract

The larger grain borer, Prostephanus truncatus (Horn) is an invasive insect pest species of global economic concern. It however remains unknown how P. truncatus succeeds under increasing temperatures and desiccation effects associated with projected climate change. Here, we investigated the effects of desiccation and high‐temperature stress on physiological fitness of P. truncatus larvae and adults. Specifically, we measured critical thermal maxima, heat knockdown time and water loss rates following heat and desiccation acclimation. Results showed beneficial heat acclimation effects on heat tolerance (critical thermal maxima and heat knockdown time). Similarly, desiccation acclimation significantly improved both heat tolerance traits, indicating cross‐tolerance effects, not for heat knockdown time in larvae. In all cases, adults exhibited more improved heat tolerance than larvae. Conversely, heat acclimation increased water loss rates, and more so in larvae than adults. Improved heat tolerance plus abiotic stress cross‐tolerance of P. truncatus may explain its enhanced physiological and ecological fitness in dry tropical and changing climate environments. These results are important in explaining the role of physiology in insect invasions and may inform pest management and forecasting.

Life‐stage‐related desiccation and starvation resistance in the biological control agent Neolema abbreviata

“…However, this is contrary to the current results which indicate crosssusceptibility of critical thermal limits to desiccation. Nevertheless, the results are not in keeping with a recent study by Mutamiswa et al (2021) that showed improved heat tolerance following desiccation pre-treatment in related beetle, Prostephanus truncatus (Horn), indicating that responses to dehydration conditions are species-dependent.…”

“…Desiccation resistance can be defined as the ability of an organism to reduce water loss and it is an essential trait in combating drought stress and survival in arid habitats (Kalra et al, 2017;Krupp et al, 2020). Desiccation resistance reportedly varies across geographic clines and body mass (Guedes et al, 2015;Bujan et al, 2016), size and sex (Tejeda et al, 2014), age (Weldon & Taylor, 2010), as well as life stage and species (Weldon et al, 2013;Bujan et al, 2016;Mutamiswa et al, 2021). In order to reduce desiccation stress, insects convert stored fat into metabolic water, reserve free water from the food they consume (e.g., honeydew or nectar), increase reabsorption of water in the rectum, minimize opening of the spiracles, and tolerate significant amounts of water loss (Gibbs et al, 2003;Bujan et al, 2016;Weldon et al, 2016Kellermann et al, 2018.…”

Hydric effects on thermal tolerances influence climate vulnerability in a high‐latitude beetle

“…The relationship between water loss rates and CT max may be related to exposure to certain environmental conditions (Renault et al, 2005; Terblanche et al, 2005, 2006). Correlations between CT max and metrics of water loss physiology support evaporative cooling as a mechanism allowing insects to tolerate warmer temperatures (Bujan et al, 2016; Mutamiswa et al, 2021; Nervo et al, 2021; Overgaard et al, 2012; Rezende et al, 2011). However, studies have also found negative correlations between water loss rates and CT max and point to alternative mechanisms, such as pilosity or sculpturing of the cuticle (Buxton et al, 2021) or effects of dehydration (Johnson & Stahlschmidt, 2020).…”

Geographic dispersion of invasive crop pests: the role of basal, plastic climate stress tolerance and other complementary traits in the tropics

“…This dispersal edge is likely necessitated by its inherent high basal starvation and desiccation stress (29). Moreover, ISR has also been reported in invasive stored grain pest P. truncatus (31). As such, it appears that common prolific pest invaders have high basal stress resistance and ISR (19**) and this potentially mediates geographic dispersion.…”