Abstract Development can play a critical role in how organisms respond to changes in the environment. Tolerance to environmental challenges can vary during ontogeny, with individual- and population-level impacts that are associated with the timing of exposure relative to the timing of vulnerability. In addition, the life history consequences of different stressors can vary with the timing of exposure to stress. Salinization of freshwater ecosystems is an emerging environmental concern, and habitat salinity can change rapidly due, for example, to storm surge, runoff of road deicing salts, and rainfall. Elevated salinity can increase the demands of osmoregulation in freshwater organisms, and amphibians are particularly at risk due to their permeable skin and, in many species, semi-aquatic life cycle. In three experiments, we manipulated timing and duration of exposure to elevated salinity during larval development of southern toad (Anaxyrus terrestris) tadpoles and examined effects on survival, larval growth, and timing of and size at metamorphosis. Survival was reduced only for tadpoles exposed to elevated salinity early in development, suggesting an increase in tolerance as development proceeds; however, we found no evidence of acclimation to elevated salinity. Two forms of developmental plasticity may help to ameliorate costs of transient salinity exposure. With early salinity exposure, the return to freshwater was accompanied by a period of rapid compensatory growth, and metamorphosis ultimately occurred at a similar age and size as freshwater controls. By contrast, salinity exposure later in development led to earlier metamorphosis at reduced size, indicating an acceleration of metamorphosis as a mechanism to escape salinity stress. Thus, the consequences of transient salinity exposure were complex and were mediated by developmental state. Salinity stress experienced early in development resulted in acute costs but little long-lasting effect on survivors, while exposures later in development resulted in sublethal effects that could influence success in subsequent life stages. Overall, our results suggest that elevated salinity is more likely to affect southern toad larvae when experienced early during larval development, but even brief sublethal exposure later in development can alter life history in ways that may impact fitness.
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Responses of Manduca sexta larvae to heat waves
ABSTRACT Climate change is increasing the frequency of heat waves and other extreme weather events experienced by organisms. How does the number and developmental timing of heat waves affect survival, growth and development of insects? Do heat waves early in development alter performance later in development? We addressed these questions using experimental heat waves with larvae of the tobacco hornworm, Manduca sexta. The experiments used diurnally fluctuating temperature treatments differing in the number (0–3) and developmental timing (early, middle and/or late in larval development) of heat waves, in which a single heat wave involved three consecutive days with a daily maximum temperature of 42°C. Survival to pupation declined with increasing number of heat waves. Multiple (but not single) heat waves significantly reduced development time and pupal mass; the best models for the data indicated that both the number and developmental timing of heat waves affected performance. In addition, heat waves earlier in development significantly reduced growth and development rates later in larval development. Our results illustrate how the frequency and developmental timing of sublethal heat waves can have important consequences for life history traits in insects.
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- Award ID(s):
- 2029156
- NSF-PAR ID:
- 10289203
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- Volume:
- 224
- Issue:
- 7
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Populations of insects can differ in how sensitive their development, growth, and performance are to environmental conditions such as temperature and daylength. The environmental sensitivity of development can alter phenology (seasonal timing) and ecology. Warming accelerates development of most populations. However, high-elevation and season-limited populations can exhibit developmental plasticity to either advance or prolong development depending on conditions. We examine how diurnal temperature variation and daylength interact to shape growth, development, and performance of several populations of the montane grasshopper, Melanoplus boulderensis , along an elevation gradient. We then compare these experimental results to observed patterns of development in the field. Although populations exhibited similar thermal sensitivities of development under long-day conditions, development of high-elevation populations was more sensitive to temperature under short-day conditions. This developmental plasticity resulted in rapid development of high elevation populations in short-day conditions with high temperature variability, consistent with their observed capacity for rapid development in the field when conditions are permissive early in the season. Notably, accelerated development generally did not decrease body size or alter body shape. Developmental conditions did not strongly influence thermal tolerance but altered the temperature dependence of performance in difficult-to-predict ways. In sum, the high-elevation and season-limited populations exhibited developmental plasticity that enables advancing or prolonging development consistent with field phenology. Our results suggest these patterns are driven by the thermal sensitivity of development increasing when days are short early in the season compared to when days are long later in the season. Developmental plasticity will shape phenological responses to climate change with potential implications for community and ecosystem structure.more » « less
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Abstract When thermal tolerances differ between interacting species, extreme temperature events (heat waves) will alter the ecological outcomes. The parasitoid wasp
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1. Temperature strongly influences the rates of physiological processes in insects, including the herbivore
Manduca sexta and its larval endoparasitoidCotesia congregata . Parasitisation byC. congregata decreases the growth and consumption of food by larvalM. sexta . However, the effects of temperature on parasitised caterpillars and the developing wasp larvae are largely unknown.2. In this study, parasitised and unparasitised caterpillars were reared at three constant temperatures (20, 25 and 30 °C) throughout larval development. Caterpillar mass gain and consumption were monitored daily until wandering (unparasitised control group) or wasp emergence (parasitised group) was observed. Development time and survival to emergence were measured as metrics of parasitoid performance.
3. Parasitised
M. sexta developed more slowly than unparasitised controls, but had similar cumulative consumption until the terminal instar. Parasitised caterpillars with relatively large parasitoid loads had higher rates of consumption and growth than those with smaller loads. Both temperature and parasitoid load strongly affected wasp success. Mean development time to wasp emergence increased with low temperatures and with large loads. The combination of warm temperature and large parasitoid loads greatly reduced wasp survival.4. These results demonstrate the interactive effects of rearing temperature and parasitisation on host consumption and growth rates throughout larval development. In addition, wasp performance was affected by the interaction of temperature and parasitoid load size. High temperatures alter the dynamics of the interaction between the parasitoid and its caterpillar host, which could have far‐reaching impacts as the global temperatures continue to rise.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1242/jeb.236505
