Insect adaptations to cold and changing environments

Abstract

Abstract-A review of insect adaptations for resistance to cold and for life-cycle timing reveals the complexity of the adaptations and their relationships to features of the environment. Cold hardiness is a complex and dynamic state that differs widely among species. Surviving cold depends on habitat choice, relationships with ice and water, and synthesis of a variety of cryoprotectant molecules. Many aspects are time-dependent and are integrated with other factors such as taxonomic affinity, resource availability, natural enemies, and diapause. Timing adaptations reflect the fact that all environments change over many different time frames, from days to thousands of years. Environments differ in severity and in the extent, nature, variability, and predictability of change, as well as in how reliably cues indicate probable conditions in the future. These differences are reflected by a wide range of insect life-cycle systems, life-cycle delays, levels of responsiveness to various environmental signals, genetic systems, and circadian responses. In particular, the degree of environmental change, its predictability on different time frames, and whether it can be monitored effectively dictate the balance between fixed and flexible timing responses. These same environmental features have to be characterized to understand cold hardiness, but this has not yet been done. Therefore, the following key questions must be answered in order to put cold hardiness into the necessary ecological context: How much do conditions change? How consistent is the change? How reliable are environmental signals?Résumé-La présente rétrospective des adaptations pour la résistance au froid et l'ajustement temporel des cycles biologiques illustre la complexité des adaptations et leurs relations aux caractéristiques du milieu. La résistance au froid est un état dynamique et complexe qui varie considérablement d'une espèce à l'autre. La survie au froid dépend du choix de l'habitat, des relations avec la glace et l'eau et de la synthèse d'une gamme de molécules cryoprotectrices. Plusieurs des aspects sont reliés au temps et sont aussi intégrés à d'autres facteurs, tels que l'affinité taxonomique, la disponibilité des ressources, les ennemis naturels et la diapause. Les adaptations d'ajustement temporel sont reliées au fait que tous les milieux changent à des échelles temporelles multiples, allant de jours à plusieurs millénaires. Les milieux différent entre eux quant à la rigueur et à l'étendue, la nature, la variabilité et la prévisibilité du changement; de plus, les indices des conditions futures probables y sont plus ou moins fiables. Ces différences se reflètent dans les systèmes de cycles biologiques des insectes, les délais dans les cycles biologiques, les degrés de réaction aux divers signaux environnementaux, les systèmes génétiques et les réponses circadiennes. En particulier, le degré de changement environnemental, sa prévisibilité aux différentes échelles temporelles et la possibilité d'en faire un suivi efficace déterminent l'équilibr...

Cold tolerance and trehalose accumulation in overwintering larvae of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae)

“…Trehalose may operate as a cryoprotectant against cold injury by stabilizing proteins and/or membranes at low temperatures (Rojas et al, 1991(Rojas et al, , 1994Ring & Danks, 1998). It also may reduce the melting point, and hence the freezing point, by osmotic effects (Danks, 2006). It is noteworthy that exogenous trehalose helps protect a variety of organisms against freezing (Leslie et al, 1995;Pellerin-Mendes et al, 1997;Diniz-Mendes et al, 1999;Zhou et al, 2006).…”

Insects in Fluctuating Thermal Environments

“…The environmental temperature in terrestrial habitats fluctuates on multiple time scales (36,80). The amplitude of daily thermal fluctuations varies by season and habitat (92), and can be over 30°C (102).…”

The occurrence of summer diapause in the large white butterfly Pieris brassicae (Lepidoptera: Pieridae): A geographical perspective

“…The two strategies differ fundamentally in life cycle plasticity. Univoltine species are closely adapted to certain seasonal conditions, a mechanism associated with the optimal exploitation of seasonally limited food resources or for limiting competition with other species (Danks, 2006b). In typically univoltine species, a developmental arrest occurs at a fixed stage in ontogeny and is induced by endogenous mechanisms (Koš ál, 2006).…”