Supplementary information Tolerance landscapes in thermal ecology E.L. Rezende, L. E. Castañeda and M. Santos. Measuring thermal tolerance .................................................................. 2 Static versus ramping assays .................................................................. 2 Fig. S1 – Building a thermal tolerance landscape ..................................... 6 Fig. S2 – The tolerance landscape and subordinate traits .......................... 7 Body mass and thermal inertia ............................................................... 8 Appendix S1 ........................................................................................ 10 Appendix S2 ........................................................................................ 12 References ........................................................................................... 13 1 Measuring thermal tolerance The thermal landscape can be readily estimated from knockdown time estimates obtained across different temperatures (Fig. S1). Given an adequate sample size, TDT curves can be estimated not only for the median lethal time in which 50% of individuals succumb to heat, which roughly corresponds to the average knockdown times (see Cooper et al. 2008), but also for other lethal time values. Briefly, individuals are submitted to different constant stressful temperatures and their knockdown times are recorded (i.e., static assay, e.g., Santos et al. 2011). The time taken for a given fraction of the sample to collapse (say, 90% of all individuals) in each temperature is then estimated. Subsequently, a TDT curve describing the isocline for this survival probability (= 0.1 in this example) can be readily calculated with a regression of log-transformed time estimates against T (eqn. 1). One can then build thermal tolerance landscape by superimposing TDT curves describing different survival probability isoclines (Fig. S1). STATIC VERSUS RAMPING ASSAYS The proposed framework suggests that, deviations due to varying cumulative thermal effects and hardening aside, static and ramping protocols provide different estimates of a single underlying relationship between thermal tolerance and time (see fig. 3b in Santos et al. 2011). Nonetheless, a systematic analysis of thermal tolerance curves must take into account these deviations and their potential effects on the quantification of parameters CTmax and z. Whereas the effects of hardening are relatively straightforward to control, methodology has such a great impact of estimates of thermal tolerance (Lutterschmidt and Hutchison 1997; Chown et al. 2009; Santos et al. 2011; Ribeiro et al. 2012) that it may jeopardize comparative 2 efforts, the quest for general patterns and, more importantly, the validation of results (Rezende and Santos 2012). Circumventing these issues requires an understanding of the pros and cons of different methods and, ultimately, a concerted effort to employ a standardized methodology. We presently advocate for the use of static assays at different temperatures because thermal tolerance varies both with the intensity and the duration of the heat stress, and neither are independent nor controlled in ramping assays. Without understanding how the total cumulative thermal stress resulting in impaired physiological function changes with temperature and time, it is virtually impossible to compare estimates from assays obtained with different ramping protocols (e.g., it is unclear whether a starting temperature of 40 C and a ramping rate of 0.05 C min 1 results on a higher thermal challenge than a starting temperature of 38 C and a rate of 0.1 C min 1). Because the intensity and duration of the thermal stress is and heating rates, their determined by the interaction between starting temperatures effects cannot be readily partitioned or controlled by statistical means (see Rezende et al. 2011). Conversely, in static assays the intensity and duration of the thermal stress are orthogonal to one another because temperature is kept constant. These assays are more adequate for analyses at the population level because they permit the quantification of the death rate constant k, which can be directly compared across species measured at the same temperatures (additionally, lethal times and the intensity of selection can be readily extrapolated from k for different scenarios). For the same reason, regression models to estimate CTmax and z differ between protocols. Parameter estimation with static assays involves ordinary least squares (OLS), including T as and log10 t as the independent and dependent variable, without and with measurement 3 error, respectively (CTmax and z are then calculated from the slope and intercept, see main text). In ramping assays, both T and log10 t involve measurement error, hence OLS results may be jeopardized because it attempts to minimize a sum of squared errors that is not orthogonal to neither T or log10 t. Measurement accuracy is also expected to be lower in ramping assays, primarily because it is easier to maintain a constant temperature than temperatures increasing at a constant rate (e.g., this probably explains some of the contradictory results listed in Rezende and Santos 2012). Failing to detect when an animal collapses will result in error in knockdown time in static assays, and in knockdown time and temperature in ramping assays (see Castañeda et al. 2012). Thermal inertia may also be more problematic for ramping assays, particularly those employing fast rates of temperature increase, than static assays in which Ta and Tb eventually reach thermal equilibrium (eqn S1 and S2). Taken together, these factors might explain, for instance, why heat tolerance in Drosophila is seemingly unaffected by water status when assayed with ramping protocols (Overgaard et al. 2012) and highly dependent on humidity when comparisons involve static assays at a common temperature (Maynard Smith 1957; Bubliy et al. 2012). To summarize, estimates obtained with ramping assays are, in principle, suitable for parameter estimation. However, in practice it is advisable to focus on measurements of knockdown times at different temperatures, to ensure that measurement noise is minimal and the statistical power to detect potentially relevant associations is maximized (see also Santos et al. 2011). Differences in goodness of fit between analyses employing estimates obtained with static versus ramping assay support these concerns: whereas the semi-logarithmic relationship explains 98.8% of the variation in knockdown times measured in D. subobscura at different 4 temperatures (r2 = 0.988; see Fig. 1), this value drops to roughly 50.7% when analyses are repeated pooling mean knockdown temperatures and times of G. pallidipes estimated with different ramping assays (r2 = 0.507; values from fig. 1a in Terblanche et al. 2007, who reported r2 = 0.576 assuming a linear relation between knockdown temperature and time). If this anecdotic observation happens to be general, then ramping assays should be avoided during the estimation of parameters CTmax and z of TDT curves. 5 Fig. S1 – Building a thermal tolerance landscape from experimental data. Top left. Simulated datasets illustrating the outcome of static assays at different temperatures, with individuals measured in each temperature slightly displaced to better visualize the data. Top right. Cumulative mortality curves in time allow the estimation of multiple lethal times LT in which a defined fraction of the population collapses, as demonstrated in this example for LT10, LT50 and LT90. Bottom left. The association between these estimates of LT (log10-transformed) and temperature is described by two parameters (intercept and slope) that can be easily calculated with ordinary least square regressions and back-transformed to obtain CTmax and z (see eqns 1 and 2). Bottom right. The regressions plotted as multiple TDT curves, which depict where the isoclines of survival probability lie in the thermal tolerance landscape. 6 Fig. S2 – Subordinate traits and break points in a thermal tolerance landscape. Top. The proposed model describes a linear relationship between tolerated temperatures and log-transformed time, as shown here for Drosophila melanogaster (data from static assays compiled from Mitchell & Hoffmann 2010; Parkash et al. 2010; Sgrò et al. 2010; Overgaard et al. 2011 and Kimura 2004). Bottom. TDT curves at the organismal level likely reflect the interaction between multiple traits at lower levels of organization, as shown schematically here. Based on the dose-response relationship, cumulative effects of temperature on subordinate traits may result in curves of decaying performance that resemble TDT curves. This conceptual model provides a temporal component to the thermobiological scale proposed by Vannier (1994) and accounts for the existence of different proxies of thermal tolerance (lethal and non-lethal) that can vary with the nature of the assay. For instance, whereas enzyme denaturation and metabolic imbalance during a thermal challenge can be lethal, other end points such as the onset of muscle spasms or loss of motor coordination are non-lethal and may give rise to seemingly different results. This model can also explain, from a physiological perspective, the presence of break-points along the TDT curve (Santos et al. 2011). 7 BODY MASS AND THERMAL INERTIA The proposed approach is highly general and applicable to other systems, being limited primarily by the thermal tolerance and environmental data available for hypothesis testing. This is particularly true for small organisms in which thermal inertia is not a concern, and even some time lag between ambient temperature Ta and body temperature Tb (within the range of minutes) may not alter dramatically the predictions of the model. However, for larger organisms thermal inertia may have an impact on estimates of thermal tolerance measured in the laboratory and on Tb in the field. The impact of thermal inertia on these variables can be estimated with knowledge of the time constant (Bell 1980; Stevenson 1985; Huey et al. 1992), which can be measured empirically or estimated from allometry (Lactin and Johnson 1998). According to simplified heat transfer models: dTb (t) Ta (t) Tb (t) . dt eqn S1 The solution of this differential equation will have the form f (Ta ) e(t / ), and (min) can be defined as the time it takes Tb to reach 1 – 1/e = 63.2% of its final asymptotic value. Thus, in a static assay in which animals are initially submittedto a step change in Ta (from room temperature to T; eqn 1), the time t necessary for T to drop to levels corresponding to a 1% of T(t0 ) corresponds to t ln(1/0.01) . For example, t < 5 min when 1.086 min , which can be contrasted against the total duration of a 8 static assay to analyze to what extent thermal inertia might affect knockdown times estimates. To quantify the impact of thermal inertia during warming conditions, which apply both to ramping assays and estimations of Tb in the field, Huey et al. (1992) demonstrated that the maximum lag between Ta and Tb is: Ta (t) Tb (t) b , eqn S2 where b ( C min 1 ) corresponds to the rate of temperature increase. Consequently, the absolute maximum lag between Ta and Tb for an organism with = 1 min will be small for typical fast ramping experiments employing heating rates of 0.5Cmin 1, and virtually negligible in the field (see fig. 1 in Terblanche et al. 2011). Because encounters warming rates in the field are generally low (unless the organism contrasting Ta during displacement from one microenvironment to another), larger values of seem to be more of a concern during estimations of thermal tolerance in the laboratory than for extrapolations to field conditions. 9 Appendix S1. Thermal death time parameters calculated from heat tolerance measurements Species Cydia pomonella Plodia interpunctella Amyelois transitella Ceratitis capitata Anastrepha ludens Tribolium castaneum Bactrocera latifrons Ceratitis capitata Bactrocera cucurbitae Bactrocera dorsalis Bactrocera latifrons Ceratitis capitata Ceratitis capitata Bactrocera cucurbitae Bactrocera dorsalis Stegobium paniceum Cataglyphis rosenhaueri Cataglyphis velox Drosophila subobscura Cimex lectularius Anopheles gambiae Drosophila melanogaster Deleatidium sp Sephlebia dentata Aoteapsyche colonica Pyconocentria evecta Deleatidium autumnale Class Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Stage last instar last instar last instar last instar last instar last instar egg egg egg egg third instar third instar third instar third instar third instar first instar adult adult adult adult egg third instar larvae larvae larvae larvae nymph Habitat terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial aquatic terrestrial aquatic aquatic aquatic aquatic aquatic LT 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 50 100 100 50 100 100 50 50 50 50 50 50 CTmax 53.96 51.5 54.58 51.23 50.17 52.34 50.14 50.22 49.24 50.01 50.66 50.25 49.71 50.67 50.66 61.57 53.53 60.03 41.4 48.84 48.59 44.05 48.84 44.23 37.91 59.58 40.06 10 z 4.35 3.85 3.85 3.33 3.45 2.44 2.98 3.16 3.03 3.21 3.7 3.03 3.17 3.87 3.06 6.47 3.92 6.26 3.93 4 3.04 3.4 7 5.48 3.18 9.3 4.24 r2 0.996 0.998 0.987 0.999 0.997 0.993 0.947 0.986 0.994 0.997 0.997 0.979 0.977 0.998 0.971 0.936 0.935 0.959 0.988 0.995 0.991 0.998 0.997 0.999 0.992 0.964 0.991 Reference Tang et al. 2007 Table 6.3 Tang et al. 2007 Table 6.3 Tang et al. 2007 Table 6.3 Tang et al. 2007 Table 6.3 Tang et al. 2007 Table 6.3 Tang et al. 2007 Table 6.3 Armstrong et al. 2009 Table 5 Armstrong et al. 2009 Table 5 Armstrong et al. 2009 Table 5 Armstrong et al. 2009 Table 5 Armstrong et al. 2009 Table 6 Armstrong et al. 2009 Table 6 Armstrong et al. 2009 Table 6 Armstrong et al. 2009 Table 6 Armstrong et al. 2009 Table 6 Abdelghany et al. 2010 Table3 Cerda and Retana 2000 Fig3 Cerda and Retana 2000 Fig3 Maynard-Smith 1957 Fig1 Pereira et al. 2009 Fig2 Huang et al. 2006 Table1 Feder et al. 1997 Fig7 Quinn et al. 1994 Table1 Quinn et al. 1994 Table1 Quinn et al. 1994 Table1 Quinn et al. 1994 Table1 Cox and Rutherford 2000 Fig2 Trogoderma granarium Sphaerium novaezelandiae Argopecten purpuratus Semele corrugata Semele solida Gari solida Donax vittatus Donax semistriatus Donax trunculus Tellina fabula Tellina tenuis Tellina tenuis Cardium glaucum Cardium tuberculatum Cardium edule Ameiurus nebulosus Semotilus atromaculatus Rhinichthys atratulus Salmo salar Salvelinus frontinalis Oncorhynchus tshawytscha Cristivomer namaycush Trematomus bernacchii Trematomus hansoni Trematomus borchgrevinki Salvelinus confluentus Fundulus parvipinnis Girella nigricans Atherinops affinis Insecta Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Bivalvia Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii Actinopterygii larvae adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult adult juvenile adult young young terrestrial aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic aquatic 100 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 60.01 44.99 47.15 49.04 50.28 43.8 38.39 39.34 45.03 33.53 40.13 42.78 41.31 40.83 49.71 36.4 35.86 34.57 32.52 31.94 30.15 29.36 16.99 16.96 17.87 34.87 42.14 38.15 34.59 11 4.22 3.84 6.01 5.87 6.91 5.39 2.87 2.71 3.55 2.02 2.68 3.28 2.04 2.99 5.3 1.35 1.9 1.32 1.78 2 1.34 1.47 3.1 3.03 3.73 2.83 1.65 2.09 0.82 0.911 0.994 0.92 0.985 0.937 0.988 0.902 0.854 0.957 0.889 0.868 0.96 0.921 0.911 0.975 0.987 0.969 0.984 0.988 0.993 0.955 0.993 0.972 0.932 0.974 0.999 0.991 0.995 0.967 Cotton 1950 in Strang1992 Quinn et al. 1994 Table1 Urban 1994 Fig2 Urban 1994 Fig2 Urban 1994 Fig2 Urban 1994 Fig2 Ansell et al. 1980 Fig1A tacc=20 Ansell et al. 1980 Fig1B tacc=20 Ansell et al. 1980 Fig1C tacc=20 Ansell et al. 1980a Fig1A tacc=20 Ansell et al. 1980a Fig1B tacc=20 Ansell et al. 1980a Fig1C tacc=20 Ansell et al. 1981 Fig1A tacc=20 Ansell et al. 1981 Fig1B tacc=20 Ansell et al. 1981 Fig1C tacc=20 Brett 1956 Fig2 Brett 1956 Fig2 Brett 1956 Fig2 Brett 1956 Fig2 Brett 1956 Fig2 Brett 1956 Fig2 Brett 1956 Fig2 Somero and DeVries 1967 Table1 Somero and DeVries 1967 Table1 Somero and DeVries 1967 Table1 Selong et al. 2011 Fig1 Doudoroff 1945 Fig2 Doudoroff 1945 Fig2 Doudoroff 1945 Fig2 Appendix S2. Thermal death time parameters calculated from cold tolerance measurements Species Tribolium castaneum Cryptolestes ferrugineus Sitophilus granarius Alphitobius diaperinus Lasioderma serricone Lasioderma serricone Lasioderma serricone Lasioderma serricone Stegobium paniceum Callosobruchus maculatus Callosobruchus maculatus Oryzaephilus surinamensis Sitophilus granarius Sitophilus granarius Sitophilus granarius Sitophilus oryzae Tribolium castaneum Tribolium confusum Tineola bisselliella Tineola bisselliella Anagasta kuhniella Plodia interpunctuella Class Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Insecta Stage all all all adult egg larvae pupae adult adult pupae egg adult adult egg larvae adult all all egg larvae all all Habitat terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial terrestrial LT 50 50 50 50 50 50 50 50 50 50 50 100 100 100 100 100 100 100 100 100 100 100 CTmin -85.17 -100.96 -35.26 -33.05 -23.05 -33.03 -26.44 -24.35 -22.19 -27.94 -32.58 -107.16 -36.12 -59.23 -48.78 -38.98 -35.28 -34.31 -47.32 -49.18 -40.23 -34.94 12 z’ 17.09 20.60 8.25 9.36 7.07 9.21 7.36 6.47 6.02 6.42 9.25 23.03 7.11 12.65 9.79 8.98 7.70 7.37 9.73 8.71 7.21 6.11 r2 0.916 0.992 0.988 0.934 0.995 0.921 0.874 0.966 0.961 0.958 0.966 0.965 0.937 0.915 0.96 0.965 0.934 0.917 0.965 0.878 0.952 0.95 Reference Fields 1992 Fig1 Fields 1992 Fig1 Fields 1992 Fig1 Renault et al. 2004 Fig2 Imai and Harada Table1 Imai and Harada Table1 Imai and Harada Table1 Imai and Harada Table1 Abdelghany et al. 2010 Table4 Loganathan et al. 2011 Tables4,5 Loganathan et al. 2011 Tables4,5 Mathlein 1961 in Strang 1992 Back and Cotton1924 in Strang 1992 Mathlein 1961 in Strang 1992 Mathlein 1961 in Strang 1992 Back and Cotton1924 in Strang 1992 Cotton 1950 in Strang 1992 Cotton 1950 in Strang 1992 Back and Cotton 1927 in Strang 1992 Back and Cotton 1927 in Strang 1992 Cotton 1950 in Strang 1992 Cotton 1950 in Strang 1992 References Abdelghany, A.Y., Awadalla, S.S., Abdel-Baky, N.F., El-Syrafi, H.A, & Fields, P.G. (2010) Effect of high and low temperatures on the drugstore beetle (Coleoptera: Anobiidae). J. Econ. Entomol., 103, 1909–1914. Ansell, A.D., Barnett, P.R.O., Bodoy, A. & Massé, H. (1980) Upper Temperature Tolerances of Some European Molluscs II. Donax vittatus, D. semistriatus and D. trunculus. Mar. Biol., 58, 41-46. Ansell, A.D., Barnett, P.R.O., Bodoy, A. & Massé, H. (1980a) Upper Temperature Tolerances of Some European Molluscs. I Tellina fabula and T. tenuis. Mar. Biol., 58, 33-39. Ansell, A.D., Barnett, P.R.O., Bodoy, A. & Massé, H. (1981) Upper Temperature Tolerances of Some European Molluscs. III. Cardium glaucum, C. tuberculatum and C. edule. Mar. Biol., 65, 177-183. Armstrong, J.W., Tang, J. & Wang, S. (2009) Thermal death kinetics of Mediterranean, Malasyan, melon and oriental fruit fly (Diptera: Tephritidae) eggs and third instars. J. Econ. Entomol, 102, 522–532. Bell, C.J. (1980) The scaling of thermal inertia in lizards. J. Exp. Biol., 86, 79 – 85. Brett, J.R. (1956) Some principles in the thermal requirements of fishes. Quat. Rev. Biol., 31, 75-87. Bulbiy, O.A., Kristensen, T.N., Kellermann, V. & Loeschcke, V. (2012) Humidity affects genetic architecture of heat resistance in Drosophila melanogaster. J. Evol. Biol., 25, 1180-1188. Castañeda, L.E., Calabria, G., Betancourt, L.A., Rezende, E.L. & Santos, M. (2012) Measurement error in heat tolerance assays. J. Therm. Biol. 37: 432-437. 13 Cerdá, X. & Retana, J. (2000) Alternative strategies by thermophilic ants to cope with extreme heat: individual versus colony level traits. Oikos, 89, 155 – 163. Chown, S.L., Jumbam, K.R., Sørensen, J.G. & Terblanche, J.S. (2009) Phenotypic variance, plasticity and heritability estimates of critical thermal limits depend on methodological context. Funct. Ecol., 23, 133–140. Cooper, B.S., Williams, B.H. & Angilletta, M.A. (2008) Unifying indices of heat tolerance in ectotherms. J. Therm. Biol., 33, 320-323. Cox, T.J. & Rutherford J.C. (2000) Thermal tolerances of two stream invertebrates exposed to diumally varying temperature. New Zeal. J. Marin. Freshwat. Res., 34, 203-208. Doudoroff, P. (1945) The resiatance and acclimation of marine fishes to temperature changes. II Experiments with Fundulus and Atherinops. Biol. Bull., 88, 194206. Feder, M.E., Blain, N. & Figureas, H. (1997) Natural thermal stress and heat-shock protein expression in Drosophila larvae and pupae. Funct. Ecol., 11,90-100. Fields, P.G. (1992) The control of stored-product insects and mites with extreme temperatures. J. Stor. Prod. Res., 28, 89-118. Huang, J., Walker, E.D, Vulule, J. & Miller, J.R. (2006) Daily temperature profiles in and around Western Kenyan larval habitats of Anopheles gambiae as related to egg mortality. Malaria Journal, 5,87. Huey, R.B., Crill, W.D., Kingsolver, J.G. & Weber, K.E. (1992) A method for rapid measurement of heat or cold resistance of small insects. Funct. Ecol., 6, 489– 494. 14 Imai, T. & Harada, H. (2006) Low-temperature as an alternative to fumigation to disinfest stored tobacco of the cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae). Appl. Entomol. Zool., 41, 87-91. Kimura, M.T. (2004) Cold and heat tolerance of drosophilid flies with reference to their latitudinal distributions. Oecologia, 140, 442–449. Lactin, D.J. & Johnson, D.L. (1998) Convective heat loss and change in body temperature of grasshopper and locust nymphs: relative importance of wind speed, insect size and insect orientation. J. Therm. Biol., 23, 5 – 13. Loganathan, M., Jayas, D.S., Fields, P.G. & White, N.D.G. (2011) Low and high temperatures for the control of cowpea beetle, Callosobruchus maculatus (F.) (coleoptera: Bruchidae) in chickpeas. J. Stor. Prod. Res., 47, 244 – 248. Lutterschmidt, W. I. & Hutchinson, V. H. (1997) The critical thermal maximum: data to support the onset of spasms as the definitive end point. Can. J. Zool., 75, 1553-1560. Maynard Smith, J. (1957) Temperature tolerance and acclimatization in Drosophila subobscura. J. Exp. Biol., 34, 85-96. Mitchell, K.A.& Hoffmann, A.A. (2010) Thermal ramping rate influences evolutionary potential and species differences for upper thermal limits in Drosophila. Funct. Ecol., 24, 694-700. Overgaard, J., Kristensen, T.N., Hoffmann, A.A., Mitchell, K.A. & Hoffmann, A.A. (2011) Thermal tolerance in widespread and tropical Drosophila species: does phenotypic plasticity increase with latitude? Am. Nat., 178, S80–S96 Overgaard, J., Kristensen, T.N. & Sorensen, J.G. (2012) Validity of thermal ramping assays used to assess thermal tolerance in arthropods. PloS ONE 7: e32758. 15 Parkash, P., Sharma, V. & Kalra, B. (2010) Correlated changes in thermotoler- ance traits and body color phenotypes in montane populations of Drosophila melanogaster: analysis of within- and between-population variations. J. Zool., 280, 49–59. Pereira, R.M., Koehler, P.G., Pfiester, M. & Walker, W. (2009) Lethal effects of heat and use of localized heat treatment for control of bed bug infestations. J. Econ. Entomol., 102, 1182-1188. Quinn, J.M., Steele, G.L., hickey, C.W. & Vickers, M.L. (1994) Upper thermal tolerances of twelve New Zealand stream invertebrate species. New Zeal. J. Marin. Freshwat. Res., 28, 391-397. Renault, D., Nedved, O., Hervant, F. & Vernon, P. (2004) The importance of fluctuating thermal regimes for repairing chill injuries in the tropical beetle Alphitobius diaperinus (Coleoptera: Tenebrionidae) during exposure to low temperature. Physiol. Entomol., 29, 139-145. Rezende, E. L., Tejedo, M. & Santos, M. (2011) Estimating the adaptive potential of critical thermal limits: methodological problems and evolutionary implications. Funct. Ecol., 25, 111 – 121. Rezende, E.L. & Santos, M. (2012) Comment on ‘Ecologically relevant measures of tolerance to potentially lethal temperatures’. J. Exp. Biol., 215, 702 – 703. Ribeiro, P.L., Camacho, A. & Navas, C.A. (2012) Considerations for assessing maximum critical temperatures in small ectothermic animals: insights from leaf-cutting ants. PloS ONE, 7, e32083. Santos, M., Castañeda, L. E. & Rezende, E. L. (2011) Making sense of heat tolerance estimates in ectotherms: lessons from Drosophila. Funct. Ecol., 25, 1169 – 1180. 16 Selong, J.H., McMahon, T.E., Zale, A.V. & Barrows, F.T. (2011) Effect of temperature on growth and survival of bull trout, with application of an improved method for determining thermal tolerance in fishes. Trans. Am. Fish. Soc., 130, 1026-1037. Sgrò, C.M., Overgaard, J., Kristensen, T.N., Mitchell, K.A., Cockerell, F.E. & Hoffmann, A.A. (2010) A comprehensive assessment of geographic varia- tion in heat tolerance and hardening capacity in populations of Drosophila melanogaster from eastern Australia. J. Evol. Biol., 23, 2484–2493. Somero, G.N. & De Vries A.L. (1967) Temperature tolerance in some arctic fishes. Science, 156, 257-258. Stevenson, R.D. (1985) Body size and limits of the daily range of body temperature in terrestrial ectotherms. Am. Nat., 125, 102-117. Strang, T. J. K. (1992) A review of published temperatures for the control of pest insects in museums. Collection Forum, 8, 41-67. Tang, J., Mitcham, E., Wang, E. & Lurie, S. (2007) Heat treatment for postharvest pest control. Pp. xiv + 349. Cromwell Press, Trowbridge. Tang, J., Ikediala, J.N., Wang, S., Hansen, J.D. & Cavalieri, R.P. (2000) Hightemperature-short-time thermal quarantine methods. Postharv. Biol. Technol., 21, 129 –145. Terblanche, J.S., Deere, J.A., Clusella-Trullas, S., Janion, C. & Chown, S.L. (2007) Critical thermal limits depend on methodological context. Proc. Roy. Soc. B, 274, 2935–2942. Terblanche, J. S., Hoffmann, A. A., Mitchell, K., Rako, L., Le Roux, P. C. and Chown, S. L. (2011) Ecologically relevant measures of tolerance to potentially lethal temperatures. J. Exp. Biol., 214, 3713 – 3725. 17 Urban, H.J. (1994) Upper temperature tolerance of ten bivalve species off Peru and Chile related to El Niño. Mar. Ecol. Prog. Ser., 107,139-145. Vannier, G. (1994) The thermobiological limits of some freezing tolerant insects: the supercooling and thermostupor points. Acta Oecologica, 15, 31–42. 18