Thermal Physiology and Developmental Plasticity of Pigmentation in the Harlequin Bug (Hemiptera: Pentatomidae)

Abstract

Traits that promote the maintenance of body temperatures within an optimal range provide advantages to ectothermic species. Pigmentation plasticity is found in many insects and enhances thermoregulatory potential as increased melanization can result in greater heat retention. The thermal melanism hypothesis predicts that species with developmental plasticity will have darker pigmentation in colder environments, which can be an important adaptation for temperate species experiencing seasonal variation in climate. The harlequin bug (Murgantia histrionica, Hemiptera: Pentatomidae, Hahn 1834) is a widespread invasive crop pest with variable patterning where developmental plasticity in melanization could affect performance. To investigate the impact of temperature and photoperiod on melanization and size, nymphs were reared under two temperatures and two photoperiods simulating summer and fall seasons. The size and degree of melanization of adults were quantified using digital imagery. To assess the effect of coloration on the amount of heat absorption, we monitored the temperature of adults in a heating experiment. Overall, our results supported the thermal melanism hypothesis and temperature had a comparatively larger effect on coloration and size than photoperiod. When heated, the body temperature of individuals with darker pigmentation increased more relative to the ambient air temperature than individuals with lighter pigmentation. These results suggest that colder temperatures experienced late in the season can induce developmental plasticity for a phenotype that improves thermoregulation in this species. Our work highlights environmental signals and consequences for individual performance due to thermal melanism in a common invasive species, where capacity to respond to changing environments is likely contributing to its spread.

Many ways to make darker flies: Intra‐ and interspecific variation in Drosophila body pigmentation components

“…Insect coloration, in particular, includes text book cases such as industrial melanism (e.g., Cook & Saccheri, 2013; van't Hof et al., 2011), mimicry (e.g., Mallet & Joron, 1999; Nadeau, 2016), and clinal variation (e.g., Bastide et al., 2014; Endler et al., 2016; Telonis‐Scott et al., 2011; Wittkopp et al., 2011). Studies in different species have illustrated the ecological significance of variation in body pigmentation, including visual communication between individuals of the same (e.g., mate attraction and mate choice; e.g., Guillermo‐Ferreira et al., 2014; Wiernasz, 1995) or of different species (e.g., predator avoidance via camouflage or aposematism; e.g., van Bergen & Beldade, 2019; Futahashi & Fujiwara, 2008; Reichstein et al., 1968), as well as thermoregulation (e.g., Rajpurohit et al., 2008; Sibilia et al., 2018). Moreover, insect pigmentation is tightly associated with various other traits that are closely related to fitness (see Mckinnon & Pierotti, 2010; Wittkopp & Beldade, 2009).…”

Thermal survival limits of larvae and adults of Sirex noctilio (Hymenoptera: Siricidae) in China

“…The comparison of the lethal temperatures of adults and larvae during dynamic warming [27] indicates that S . noctilio adults exhibit stronger heat resistance than larva during the same period.…”

Thermal Plasticity in Insects’ Response to Climate Change and to Multifactorial Environments

“…There are any examples of thermal plasticity in insects, including developmental effects and adult acclimation. Temperature-dependence has been described for many processes and traits, including sex determination (Blackmon et al, 2017), induction of diapause (Saunders, 2014), body pigmentation (Sibilia et al, 2018), behavior (Abram et al, 2017). Likewise, thermal adaptation and thermal tolerance have also been extensively studied in various insect species (Tobler et al, 2015;Mallard et al, 2018;Kellermann and van Heerwaarden, 2019).…”