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1.
Reyard Mutamiswa Vimbai Lisa Tarusikirwa Casper Nyamukondiwa Ross N. Cuthbert Frank Chidawanyika 《Physiological Entomology》2023,48(1):35-44
Global climate change is projected to increase the incidence of heat waves, their magnitude and duration resulting in insects experiencing increasing environmental stress in both natural and managed ecosystems. While studies on insect thermal tolerance are rapidly increasing, variation across developmental or juvenile stress cross-stage effects within and across generations remain largely unexplored. Yet in holometabolous insects, heat stress at an early developmental stage may influence performance and survival during later stages. Here, we investigated the effects of pupal mild heat stress on the performance of laboratory-reared adult Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) measured as longevity, critical thermal maximum (CTmax), critical thermal minima (CTmin), heat knockdown time (HKDT) and chill coma recovery time (CCRT). Pupal heat stress significantly influenced performance of B. dorsalis adults resulting in impaired longevity and heat tolerance (CTmax and HKDT) in both sexes with improved and compromised cold tolerance (CTmin and CCRT) in females and males, respectively. These findings highlight the role of juvenile stages in mediating stress responses at adult stages. For B. dorsalis, pupal heat stress largely compromised thermal tolerance implying that the species has limited potential to shift its geographic range in heat prone areas. Significant benefits in cold tolerance in females following heat stress may help in improving survival in the cold in the short-term despite restricted activity to the same traits in males. This study suggests that basal heat tolerance and not short-term compensatory thermal plasticity following heat stress may have aided the recent invasion of B. dorsalis in African landscapes. 相似文献
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3.
Helder Duarte Miguel Tejedo Marco Katzenberger Federico Marangoni Diego Baldo Juan Francisco Beltrán Dardo Andrea Martí Alex Richter‐Boix Alejandro Gonzalez‐Voyer 《Global Change Biology》2012,18(2):412-421
Predicting the biodiversity impacts of global warming implies that we know where and with what magnitude these impacts will be encountered. Amphibians are currently the most threatened vertebrates, mainly due to habitat loss and to emerging infectious diseases. Global warming may further exacerbate their decline in the near future, although the impact might vary geographically. We predicted that subtropical amphibians should be relatively susceptible to warming‐induced extinctions because their upper critical thermal limits (CTmax) might be only slightly higher than maximum pond temperatures (Tmax). We tested this prediction by measuring CTmax and Tmax for 47 larval amphibian species from two thermally distinct subtropical communities (the warm community of the Gran Chaco and the cool community of Atlantic Forest, northern Argentina), as well as from one European temperate community. Upper thermal tolerances of tadpoles were positively correlated (controlling for phylogeny) with maximum pond temperatures, although the slope was steeper in subtropical than in temperate species. CTmax values were lowest in temperate species and highest in the subtropical warm community, which paradoxically, had very low warming tolerance (CTmax–Tmax) and therefore may be prone to future local extinction from acute thermal stress if rising pond Tmax soon exceeds their CTmax. Canopy‐protected subtropical cool species have larger warming tolerance and thus should be less impacted by peak temperatures. Temperate species are relatively secure to warming impacts, except for late breeders with low thermal tolerance, which may be exposed to physiological thermal stress in the coming years. 相似文献
4.
City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community
Cities are rapidly expanding, and global warming is intensified in urban environments due to the urban heat island effect. Therefore, urban animals may be particularly susceptible to warming associated with ongoing climate change. We used a comparative and manipulative approach to test three related hypotheses about the determinants of heat tolerance or critical thermal maximum (CTmax) in urban ants—specifically, that (a) body size, (b) hydration status, and (c) chosen microenvironments influence CTmax. We further tested a fourth hypothesis that native species are particularly physiologically vulnerable in urban environments. We manipulated water access and determined CTmax for 11 species common to cities in California's Central Valley that exhibit nearly 300‐fold variation in body size. There was a moderate phylogenetic signal influencing CTmax, and inter (but not intra) specific variation in body size influenced CTmax where larger species had higher CTmax. The sensitivity of ants’ CTmax to water availability exhibited species‐specific thresholds where short‐term water limitation (8 hr) reduced CTmax and body water content in some species while longer‐term water limitation (32 hr) was required to reduce these traits in other species. However, CTmax was not related to the temperatures chosen by ants during activity. Further, we found support for our fourth hypothesis because CTmax and estimates of thermal safety margin in native species were more sensitive to water availability relative to non‐native species. In sum, we provide evidence of links between heat tolerance and water availability, which will become critically important in an increasingly warm, dry, and urbanized world that others have shown may be selecting for smaller (not larger) body size. 相似文献
5.
Lower thermal tolerance in nocturnal than in diurnal ants: a challenge for nocturnal ectotherms facing global warming
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CARLOS GARCIA‐ROBLEDO HECTOR CHUQUILLANQUI ERIN K. KUPREWICZ FEDERICO ESCOBAR‐SARRIA 《Ecological Entomology》2018,43(2):162-167
1. The thermal adaptation hypothesis proposes that because thermoregulation involves a high metabolic cost, thermal limits of organisms must be locally adapted to temperatures experienced in their environments. There is evidence that tolerance to high temperatures decreases in insects inhabiting colder habitats and microclimates. However, it is not clear if thermal limits of ectotherms with contrasting temporal regimes, such as diurnal and nocturnal insects, are also adapted to temperatures associated with their circadian activities. 2. This study explores differences in heat tolerance among diurnal and nocturnal ant species in four ecosystems in Mexico: tropical montane, tropical rainforest, subtropical dry forests, and high‐elevation semi‐desert. 3. The critical thermal maximum (CTmax), i.e. the temperature at which ants lost motor control, was estimated for diurnal and nocturnal species. CTmax for 19 diurnal and 12 nocturnal ant species distributed among 45 populations was also estimated. 4. Semi‐desert and subtropical dry forest ants displayed higher tolerances to high temperatures than did ants in tropical rainforest. The lowest tolerance to high temperatures was recorded in tropical montane forest ants. In general, among all habitats, the CTmax of nocturnal ants was lower than that of diurnal ants. 5. An increase in nocturnal temperatures, combined with lower tolerance to high temperatures, may represent a substantial challenge for nocturnal ectotherms in a warming world. 相似文献
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Insect thermal tolerance shows a range of responses to thermal history depending on the duration and severity of exposure. However, few studies have investigated these effects under relatively modest temperature variation or the interactions between short‐ and longer‐term exposures. In the present study, using a full‐factorial design, 1 week‐long acclimation responses of critical thermal minimum (CTmin) and critical thermal maximum (CTmax) to temperatures of 20, 25 and 30 °C are investigated, as well as their interactions with short‐term (2 h) sub‐lethal temperature exposures to these same conditions (20, 25 and 30 °C), in two fruit fly species Ceratitis capitata (Wiedemann) and Ceratitis rosa Karsch from South Africa. Flies generally improve heat tolerance with high temperature acclimation and resist low temperatures better after acclimation to cooler conditions. However, in several cases, significant interaction effects are evident for CTmax and CTmin between short‐ and long‐term temperature treatments. Furthermore, to better comprehend the flies' responses to natural microclimate conditions, the effects of variation in heating and cooling rates on CTmax and CTmin are explored. Slower heating rates result in higher CTmax, whereas slower cooling rates elicit lower CTmin, although more variation is detected in CTmin than in CTmax (approximately 1.2 versus 0.5 °C). Critical thermal limits estimated under conditions that most closely approximate natural diurnal temperature fluctuations (rate: 0.06 °C min?1) indicate a CTmax of approximately 42 °C and a CTmin of approximately 6 °C for these species in the wild, although some variation between these species has been found previously in CTmax. In conclusion, the results suggest critical thermal limits of adult fruit flies are moderated by temperature variation at both short and long time scales and may comprise both reversible and irreversible components. 相似文献
7.
As stream temperatures increase due to factors such as heated runoff from impervious surfaces, deforestation, and climate change, fish species adapted to cold water streams are forced to move to more suitable habitat, acclimate or adapt to increased thermal regimes, or die. To estimate the potential for adaptation, a (within individual) repeatable metric of thermal tolerance is imperative. Critical thermal maximum (CTmax) is a dynamic test that is widely used to measure thermal tolerance across many taxa and has been used in fishes for decades, but its repeatability in most species is unknown. CTmax tests increase water temperature steadily over time until loss of equilibrium (LOE) is achieved. To determine if CTmax is a consistent metric within individual fish, we measured CTmax on the same lab-held individually-marked adult brook trout Salvelinus fontinalis at three different times (August & September 2016, September 2017). We found that CTmax is a repeatable trait (Repeatability ± S.E.: 0.48 ± 0.14). CTmax of individuals males was consistent over time, but the CTmax of females increased slightly over time. This result indicates that CTmax is a robust, repeatable estimate of thermal tolerance in a cold-water adapted fish. 相似文献
8.
Quantifying intraspecific variation in heat tolerance is critical to understand how species respond to climate change. In a previous study, we recorded variability in critical thermal maxima (CTmax) by 3 °C among populations of small Iberian lizard species, which could substantially influence predictions of climate-driven activity restriction. Here, we undertake experiments to examine whether we could reproduce similar levels of heat-tolerance variability in response to water deficit. We hypothesized that deprivation of drinking water should increase variability in CTmax between populations more than deprivation of food under the theoretical expectation that the variation of the more limiting resource must trigger stronger variation in physiological performance. We measured CTmax after manipulating availability of live prey and drinking water in two populations of an arid and a mesic lizard species from the Iberian Peninsula. We quantified a mean CTmax across all studied lizards of 44.2 °C ± 0.2 SE for the arid species and 41.7 °C ± 0.3 SE for the mesic species. Using multimodel inference, we found that water deprivation (combined with food supply) caused population differences in CTmax by 3 to 4 °C which were two to three times wider than population differences due to food deprivation (combined with water supply) or to food and water provision. To highlight the need for more thermo-hydroregulatory research, we examined bias in research effort towards thermal versus hydric environmental effects on heat tolerance through a systematic literature review. We show that environmental temperature has been used five times more frequently than precipitation in ecological studies of heat tolerance of terrestrial species. Studies linking thermal tolerance of ectotherms to the interplay of air temperature and water availability are needed in the face of projected increases in aridity and drought in the 21st century, because the balance of body temperature and water resources are functionally interlinked. 相似文献
9.
Tropical ectothermic species are currently depicted as more vulnerable to increasing temperatures because of the proximity between their upper thermal limits and environmental temperatures. Yet, the acclimatory capacity of thermal limits has rarely been measured in tropical species, even though they are generally predicted to be smaller than in temperate species. We compared critical thermal maximum (CTmax) and warming tolerance (WT: the difference between CTmax and maximum temperature, Tmax), as well as CTmax acclimatory capacity of toad species from the Atlantic forest (AF) and the Brazilian Caatinga (CAA), a semi-arid habitat with high temperatures. Acclimation temperatures represented the mean temperatures of AF and CAA habitats, making estimates of CTmax and WT more ecologically realistic. CAA species mean CTmax was higher compared to AF species in both acclimation treatments. Clutches within species, as well as between AF and CAA species, differed in CTmax plasticity and we discuss the potential biological meaning of these findings. We did not find a trade-off between absolute CTmax and CTmax plasticity, indicating that species can have both high CTmax and high CTmax plasticity. Although CTmax was highly correlated to Tmax, CTmax plasticity was not related to Tmax or Tmax coefficients of variation. CAA species mean WT was lower than for AF species, but still very high for all species, diverging from other studies with tropical species. This might be partially related to over-estimation of vulnerability due to under-appreciation of realistic acclimation treatments in CTmax estimation. Thus, some tropical species might not be as vulnerable to warming as previously predicted if CTmax is considered as a shifting population parameter. 相似文献
10.
Heat tolerance in Drosophila subobscura along a latitudinal gradient: Contrasting patterns between plastic and genetic responses
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Luis E. Castañeda Enrico L. Rezende Mauro Santos 《Evolution; international journal of organic evolution》2015,69(10):2721-2734
Susceptibility to global warming relies on how thermal tolerances respond to increasing temperatures through plasticity or evolution. Climatic adaptation can be assessed by examining the geographic variation in thermal‐related traits. We studied latitudinal patterns in heat tolerance in Drosophila subobscura reared at two temperatures. We used four static stressful temperatures to estimate the thermal death time (TDT) curves, and two ramping assays with fast and slow heating rates. Thermal death time curves allow estimation of the critical thermal maximum (CTmax), by extrapolating to the temperature that would knock down the flies almost “instantaneously,” and the thermal sensitivity to increasing stressful temperatures. We found a positive latitudinal cline for CTmax, but no clinal pattern for knockdown temperatures estimated from the ramping assays. Although high‐latitude populations were more tolerant to an acute heat stress, they were also more sensitive to prolonged exposure to less stressful temperatures, supporting a trade‐off between acute and chronic heat tolerances. Conversely, developmental plasticity did not affect CTmax but increased the tolerance to chronic heat exposition. The patterns observed from the TDT curves help to understand why the relationship between heat tolerance and latitude depends on the methodology used and, therefore, these curves provide a more complete and reliable measurement of heat tolerance. 相似文献
11.
Thermal limits to survival and activity in two life stages of false codling moth Thaumatotibia leucotreta (Lepidoptera,Tortricidae)
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John S. Terblanche Katherine A. Mitchell Wilmari Uys Clancy Short Leigh Boardman 《Physiological Entomology》2017,42(4):379-388
The present study examines life stage‐related variation in the thermal limits to activity and survival in an African pest, the false codling moth Thaumatotibia leucotreta (Lepidoptera, Tortricidae). Thermal tolerance, including the functional activity limits of critical thermal maxima and minima (CTmax and CTmin respectively), upper and lower lethal temperature, and the effect of heat and cold hardening (short‐term acute plasticity), is measured across a diverse range of low or high temperature stress conditions in both larvae and adults. We also report the sum of inducible and cognate forms of the amounts of heat shock protein 70 (HSP70) as an explanatory variable for changes in thermotolerance. The results show that the larvae have high variability in CTmax and CTmin at different ramping rates and low levels of basal (innate) thermal tolerance. By contrast, the adults show high basal tolerance and overall lower variability in CTmax and CTmin, indicating lower levels of phenotypic plasticity in thermotolerance. HSP70 responses, although variable, do not reflect these tolerance or survival patterns. Larvae survive across a broader range of temperatures, whereas adults remain active across a broader range of temperatures. Life stage‐related variation in thermal tolerance is most pronounced under the slowest (most ecologically‐relevant) ramping rate (0.06 °C min–1) during lower critical thermal limit experiments and least pronounced during upper thermal limit experiments. Thus, the ramping rate can hinder or enhance the detection of stage‐related variation in thermal limits to activity and survival of insects. 相似文献
12.
Emily R. Lechner Erin M. C. Stewart Chris C. Wilson Graham D. Raby 《Journal of fish biology》2024,104(3):901-905
Critical thermal maximum (CTmax) is widely used to measure upper thermal tolerance in fish but is rarely examined in embryos. Upper thermal limits generally depend on an individual's thermal history, which molds plasticity. We examined how thermal acclimation affects thermal tolerance of brook trout (Salvelinus fontinalis) embryos using a novel method to assess CTmax in embryos incubated under three thermal regimes. Warm acclimation was associated with an increase in embryonic upper thermal tolerance. However, CTmax variability was markedly higher than is typical for juvenile or adult salmonids. 相似文献
13.
Nonofo Gotcha Honest Machekano Ross N. Cuthbert Casper Nyamukondiwa 《Insect Science》2021,28(4):1076-1086
Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change, some species cope through behavioral compensation. As temperatures and magnitudes of temperature extremes increase, animals should compensate to maintain fitness (such as through temporary behavioral shifts in activity times). Appropriate timing of activity helps avoid competition across species. Although coprophagic dung beetles exhibit species-specific temporal activity times, it is unknown whether temperature drives evolution of these species-specific temporal activity times. Using nine dung beetle species (three each of diurnal, crepuscular, and nocturnal species), we explored differences in heat stress tolerance measured as critical thermal maxima (CTmax; the highest temperature allowing activity) and heat knockdown time (HKDT; survival time under acute heat stress) across these species, and examined the results using a phylogenetically informed approach. Our results showed that day-active species had significantly higher CTmax (diurnal > crepuscular = nocturnal species), whereas crepuscular species had higher HKDT (crepuscular > nocturnal > diurnal species). There was no correlation between heat tolerance and body size across species with distinct temporal activity, and no significant phylogenetic constraint for activity. Species with higher CTmax did not necessarily have higher HKDT, which indicates that species may respond differently to diverse heat tolerance metrics. Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and, under high acute temperatures with climate change, species may shift activity times in more benign environments. These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments. 相似文献
14.
Superior basal and plastic thermal responses to environmental heterogeneity in invasive exotic stemborer Chilo partellus Swinhoe over indigenous Busseola fusca (Fuller) and Sesamia calamistis Hampson
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Reyard Mutamiswa Frank Chidawanyika Casper Nyamukondiwa 《Physiological Entomology》2018,43(2):108-119
Lepidopteran stemborers are the most destructive insect pests of cereal crops in sub‐Saharan Africa. In nature, these insects are often exposed to multiple environmental stressors, resulting in potent impact on their thermal tolerance. Such environmental stressors may influence their activity, survival, abundance and biogeography. In the present study, we investigate the effects of acclimation to temperature, starvation and desiccation on thermal tolerance, measured as critical thermal limits [critical thermal minima (CTmin) and maxima (CTmax)] on laboratory‐reared economic pest species Chilo partellus Swinhoe (Lepidoptera: Crambidae), Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae) using established protocols. Low temperature acclimation results in improved CTmin for B. fusca and C. partellus, whereas high temperature acclimation enhances the same trait for B. fusca and S. calamistis. Similarly, high temperature and starvation pretreatment improve CTmax for C. partellus relative to S. calamistis and B. fusca. In addition, starvation and desiccation pretreatments improve CTmin for all stemborer species. Furthermore, rapid cold‐hardening (RCH) enhancs CTmin for B. fusca and C. partellus, whereas rapid heat‐hardening (RHH) improves the same trait for C. partellus. However, RCH and RHH impair CTmax for all stemborer species. These findings show differential thermal tolerances after exposure to heterogeneous environmental stress habitats. Chilo partellus, of exotic origin, shows a higher magnitude of basal thermal tolerance plasticity relative to the indigenous African species S. calamistis and B. fusca. This indicates that C. partellus may have a fitness and survival advantage under climate‐induced heterogeneous environments, and also have a greater chance for geographical range expansion and invasion success compared with the indigenous B. fusca and S. calamistis. 相似文献
15.
South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating invasive global insect pest of tomato, Solanum lycopersicum (Solanaceae). In nature, pests face multiple overlapping environmental stressors, which may significantly influence survival. To cope with rapidly changing environments, insects often employ a suite of mechanisms at both acute and chronic time-scales, thereby improving fitness at sub-optimal thermal environments. For T. absoluta, physiological responses to transient thermal variability remain under explored. Moreso, environmental effects and physiological responses may differ across insect life stages and this can have implications for population dynamics. Against this background, we investigated short and long term plastic responses to temperature of T. absoluta larvae (4th instar) and adults (24–48 h old) from field populations. We measured traits of temperature tolerance vis critical thermal limits [critical thermal minima (CTmin) and maxima (CTmax)], heat knockdown time (HKDT), chill coma recovery time (CCRT) and supercooling points (SCP). Our results showed that at the larval stage, Rapid Cold Hardening (RCH) significantly improved CTmin and HKDT but impaired SCP and CCRT. Heat hardening in larvae impaired CTmin, CCRT, SCP, CTmax but not HKDT. In adults, both heat and cold hardening generally impaired CTmin and CTmax, but had no effects on HKDT, SCP and CCRT. Low temperature acclimation significantly improved CTmin and HKDT while marginally compromising CCRT and CTmax, whereas high temperature acclimation had no significant effects on any traits except for HKDT in larvae. Similarly, low and high temperature acclimation had no effects on CTmin, SCPs and CTmax, while high temperature acclimation significantly compromised adult CCRT. Our results show that larvae are more thermally plastic than adults and can shift their thermal tolerance in short and long timescales. The larval plasticity reported here could be advantageous in new envirnments, suggesting an asymmetrical ecological role of larva relative to adults in facilitating T. absoluta invasion. 相似文献
16.
We studied the thermal tolerances of Rhinella arenarum during the dry and wet seasons of the Monte Desert in San Juan Province, Argentina. This toad had differences in CTmax between dry and wet seasons, and the CTmax values were higher in the wet season (Austral summer). Operative temperature, body temperature, environmental maximal temperature, and relative humidity were related to CTmax, suggesting seasonal acclimatization of R. arenarum. Additionally, the CTmax recorded for R. arenarum was 36.2 °C, and the maximum ambient temperature recorded during the toads' activity time was 37 °C. Also, the CTmin recorded for R. arenarum was 5.3 °C and the minimum environmental temperature recorded was 7.2 °C. The wide thermal tolerance range recorded and the relationship between tolerance limits and the environmental extremes indicate that seasonal acclimatization is an effective mechanism by which toads can raise their thermal tolerance, allowing them to survive in the challenging conditions of the Monte Desert. Additional studies are needed to understand the relationship between the thermal tolerance of this desert amphibian and the environmental parameters that influence its thermal physiology. 相似文献
17.
Reyard Mutamiswa Vimbai Tarusikirwa Casper Nyamukondiwa Frank Chidawanyika 《Journal of Applied Entomology》2020,144(10):885-896
The incidence and severity of environmental stressors associated with global climate change are increasing and insects frequently face variability in temperature and moisture regimes at variable spatio-temporal scales. Coincidental with this, is increased thermal and hydric stress on insects as warming increases vapour pressure deficit (VPD), the drying power of the air. While the effects of mean temperatures on fitness are widely documented, fluctuations in both temperature and relative humidity (RH) are largely unexplored. Here, we investigated the effects of dynamic temperature and RH fluctuations (around the mean [28°C; 65% RH]) on low and high thermal tolerance of laboratory-reared adult invasive Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), measured as critical thermal minima (CTmin), critical thermal maxima (CTmax), chill coma recovery time (CCRT) and heat knockdown time (HKDT). Our results show that increased environmental amplitude significantly influenced low and high temperature responses and varied across traits tested. The highest amplitude (δ12°C; 28% RH) compromised CTmin, CCRT and HKDT traits while enhancing CTmax. Similarly, acclimation to δ3°C; 7% RH compromised both low (CTmin and CCRT) and high (CTmax and HKDT) fitness traits. Variations in fitness reported here indicate significant roles of combined thermal and moisture fluctuations on B. dorsalis fitness suggesting caveats that are worthy considering when predicting species responses to climate change. These results are significant for B. dorsalis population phenology, management, quantifying vulnerability to climate variability and may help modelling future biogeographical patterns. 相似文献
18.
Steaphan P. Hazell Constantinos Groutides Tim M. Blackburn 《Journal of insect physiology》2010,56(2):123-388
Although the impact of warming on winter limitation of aphid populations is reasonably well understood, the impacts of hot summers and heat wave events are less clear. In this study, we address this question through a detailed analysis of the thermal ecology of three closely related aphid species: Myzus persicae, a widespread, polyphagous temperate zone pest, Myzus polaris, an arctic aphid potentially threatened by climate warming, and, Myzus ornatus, a glasshouse pest that may benefit from warming. The upper lethal limits (ULT50) and heat coma temperatures of the aphid species reared at both 15 and 20 °C did not differ significantly, suggesting that heat coma is a reliable indicator of fatal heat stress. Heat coma and CTmax were also measured after aphids were reared at 10 and 25 °C for one and three generations. The extent of the acclimation response was not influenced by the number of generations. Acclimation increased CTmax with rearing temperature for all species. The acclimation temperature also influenced heat coma; this relationship was linear for M. ornatus and M. polaris but non-linear for M. persicae (increased tolerance at 10 and 25 °C). Bacteria known generically as secondary symbionts can promote thermal tolerance of aphids, but they were not detected in the aphids studied here. Assays of optimum development temperature were also performed for each species. All data indicate that M. persicae has the greatest tolerance of high temperatures. 相似文献
19.
Victor H. Gonzalez John M. Hranitz Catherine R. Percival Kristen L. Pulley Stephen T. Tapsak Thomas Tscheulin Theodora Petanidou John F. Barthell 《Ecological Entomology》2020,45(3):688-696
1. Thermal tolerance has a strong predictive power for understanding the ecology and distribution of organisms, as well as their responses to changes in land use and global warming. However, relatively few studies have assessed thermal tolerances for bees. 2. The present study aimed to determine whether the critical thermal maximum (CTmax) of carpenter bees (Apidae: genus Xylocopa Latreille) varies with different patterns of foraging activity and elevation. In addition, the influence of body size, body water content and relative age was examined with respect to their CTmax and differences in thoracic temperature (Tth) among species were evaluated. 3. The CTmax of one crepuscular (Xylocopa olivieri) and two diurnal species (Xylocopa violacea and Xylocopa iris) of carpenter bees was assessed at sea level on the Greek island of Lesvos. To detect variation as a result of elevation, the CTmax of a population of X. violacea at 625 m.a.s l. was assessed and compared with that from sea level. 4. Xylocopa olivieri displayed a similar CTmax to that of X. violacea but lower than that of X. iris. Body size, body water content, and relative age did not affect CTmax. In X. violacea, CTmax decreased with elevation and all three species have high Tth independent of ambient temperatures. 5. The results of the present study are consistent with variations in CTmax predicted by broad spatial and temporal patterns reported for other insects, including honey and bumble bees. The implications of the results are discussed aiming to understand the differences in the foraging pattern of these bees. 相似文献
20.
Maximum thermal tolerance trades off with chronic tolerance of high temperature in contrasting thermal populations of Radix balthica
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Thermal adaptation theory predicts that thermal specialists evolve in environments with low temporal and high spatial thermal variation, whereas thermal generalists are favored in environments with high temporal and low spatial variation. The thermal environment of many organisms is predicted to change with globally increasing temperatures and thermal specialists are presumably at higher risk than thermal generalists. Here we investigated critical thermal maximum (CTmax) and preferred temperature (Tp) in populations of the common pond snail (Radix balthica) originating from a small‐scale system of geothermal springs in northern Iceland, where stable cold (ca. 7°C) and warm (ca. 23°C) habitats are connected with habitats following the seasonal thermal variation. Irrespective of thermal origin, we found a common Tp for all populations, corresponding to the common temperature optimum (Topt) for fitness‐related traits in these populations. Warm‐origin snails had lowest CTmax. As our previous studies have found higher chronic temperature tolerance in the warm populations, we suggest that there is a trade‐off between high temperature tolerance and performance in other fitness components, including tolerance to chronic thermal stress. Tp and CTmax were positively correlated in warm‐origin snails, suggesting a need to maintain a minimum “warming tolerance” (difference in CTmax and habitat temperature) in warm environments. Our results highlight the importance of high mean temperature in shaping thermal performance curves. 相似文献