温度对大蜡螟生长发育和繁殖的影响

为明确不同温度对大蜡螟(Galleria mellonella L.)生长发育和繁殖的影响,在24℃、28℃和31℃三个温度条件下,采用人工饲料饲养观察了大蜡螟的生长发育和繁殖状况。结果表明,温度对大蜡螟发育历期、生长发育速率以及繁殖具有显著影响(P0. 05)。在24～31℃范围内,随着温度升高,各虫态发育历期缩短,幼虫体长增长加快,发育速率加快。在24℃下世代历期最长(47. 96 d),31℃下世代历期最短(33. 68 d)。在同一温度下,雄蛾的寿命明显较雌蛾的寿命长,但成虫寿命、产卵前期和产卵期均随着温度升高而缩短。在24℃下产卵量最高为2 781. 50粒/雌,而在31℃下产卵量最低为1 943. 17粒/雌。     

温度对青海尕海盐湖卤虫发育和种群增长的影响

1990～ 1999年对尕海卤虫的温度特性研究表明 ,无节幼虫的耐寒力比幼虫期高 - 1 7℃ ,比成虫期高- 0 9℃ ,即无节幼虫的耐寒力最强 ,幼虫对低温最敏感 ;孵化发育起始温度 9 94℃ ,幼虫发育起始温度10 33℃ ,有效积温 (℃·d)前者为 2 2 91± 2 0 8,后者为 2 6 1 2 6± 2 4 1,平均世代发育起点温度 10 2 8℃ ,有效积温 45 8 6 8± 5 7 6 0 ;依据生命表计算得出的各项生态学参数与温度存在显著的函数关系 ,其适温范围基本介于 10℃～ 39℃ ,最适温度介于 2 4 9℃～ 30 5℃ ,种群增长倍数 >2的温度范围在 15℃～ 34℃ ;依据 1993～ 1994和 1997年尕海水域温度测定资料 ,结合上述实验结果 ,得出该卤虫的年世代数为 2 6 7± 0 34个代 ,一年中有4 6 9± 0 43个生殖高峰期 ;最后一个完整世代的起始时间是 8月 10日 ;因积温不足 ,在 9月 1日以后出现的无节幼虫将不能完成到成虫期的发育 ;在 7月中旬至 9月中旬是种群生产力高峰期 ,在此期间种群的加倍时间 <30d ,内禀增长率 >0 0 2d-1,开发潜力最大。     

赤眼蜂发育速率对梯度恒温的响应

赤眼蜂发育速率对梯度恒温的响应关系到生物防治效果问题,以稻螟赤眼蜂与玉米螟赤眼蜂为例,研究了两种赤眼蜂分别在10、15、20、25、30、35、37℃梯度恒温下的相应世代发育历期,并运用直线回归模型与王-兰-丁模型两种拟合法,对温度与发育速率的关系进行了拟合。研究结果表明:温度对两种赤眼蜂的世代发育历期有明显的影响,在试验梯度温度10-37℃范围内,两种赤眼蜂的世代发育历期随温度升高而逐渐缩短。在10℃至30℃范围内,两种赤眼蜂的发育历期迅速缩短。在30℃到37℃范围内,两种赤眼蜂的发育历期变化进入一个相对平稳时期。在试验温度为30、35、37℃,稻螟赤眼蜂与玉米螟赤眼蜂的发育历期分别为7.75、7.45、7.95d和8.05、7.50、7.90d,差异不显著。通过直线回归法,可得稻螟赤眼蜂与玉米螟赤眼蜂的发育起点温度分别为5.23℃和5.24℃,有效积温分别为212.77d·℃和217.39d·℃;利用王氏模型法,得到两种赤眼蜂的发育最低温、发育最适温和发育最高温分别为7.96、18.91、38.99℃和6.97、18.87、38.99℃。稻螟赤眼蜂与玉米螟赤眼蜂在10-37℃的试验温度范围内,发育速率随温度升高而相应增大。在10-30℃范围内,两种赤眼蜂的发育速率迅速增长;在30-35℃范围内,两种赤眼蜂的发育速率进入一个相对平稳时期,超过临界高温TH后,随温度升高发育速率最终降为0。讨论了赤眼蜂发育速率对梯度恒温响应研究中应注意的梯度恒温设计和数学模型选择问题。     

温度对卷蛾分索赤眼蜂种群参数的影响

通过组建卷蛾分索赤眼蜂 Trichogrammatoidea bactrae Nagaraja在米蛾 Corcyra cephalonica(Stainton)卵上实验种群生命表的方法 ,考察了梯度恒温 17、2 0、2 3、2 6、2 9、32℃和 35℃对该蜂发育、存活和繁殖的影响。在试验温度范围内 ,卷蛾分索赤眼蜂的世代发育历期随着温度的升高而缩短 ,发育历期由 17℃时的 2 0 .77d降至 35℃时的 7.2 5 d。卷蛾分索赤眼蜂的临界发育温度为 11.92和 38.95℃ ,适宜的生长发育温区则介于 2 0～ 2 9℃之间 ,最适发育温度为 2 3.0 7℃。在适宜温度 (2 0～ 2 9℃ )范围内 ,卷蛾分索赤眼蜂的幼期存活率维持在 90 %以上 ,雌成蜂具有较长的寿命 ,7.6 7～ 10 .87d;内禀增长率 (rm)及净生殖力 (R0 ) ,分别介于 0 .2 395～ 0 .4 890和 4 2 .32～ 6 4 .2 3之间。极端温度对卷蛾分索赤眼蜂的生长发育和生殖均有明显的抑制作用 ,在 35℃时 ,其幼期存活率为 12 .98% ,雌成蜂寿命不足 1d,且不能进行正常的生殖活动。温度对卷蛾分索赤眼蜂的子代性比有着显著的影响 ,在 17～ 35℃范围 ,子代雌雄性比随着温度的升高而不断下降 ,17,2 0 ,2 3,2 6 ,2 9℃和 32℃时的子代雌雄性比分别为 6 .73,3.4 8,2 .88,2 .4 5 ,2 .4 1和 1.75 ,温度与子代性比的作用关系可用公式 s=exp(3.5 1- 0 .10     

温度对以白茶为寄主的米缟螟生长发育的影响

为探明温度对以白茶为寄主植物的产虫茶昆虫米缟螟生长发育的影响,分别设置5个温度条件(31、28、25、22、19℃),研究温度对米缟螟各虫态平均发育历期、发育速率和存活率的影响,计算各虫态发育起点温度和有效积温.结果表明:温度对米缟螟各虫态平均发育历期影响显著,除卵的发育历期随温度的升高而缩短外,幼虫、蛹及未成熟期的发育历期均在25℃达到最小值,分别为(249.53±23.83)d、(12.94±1.27)d和(273.00±24.19)d;除蛹外米缟螟各虫态发育速率与温度呈极显著相关,其中卵的发育速率与温度呈线性相关,幼虫、蛹和未成熟期则呈抛物线相关;温度显著影响各虫态存活率,卵、幼虫、蛹及未成熟期各虫态存活率均在25℃最高,分别为94.0％、73.8％、91.3％和63.4％,22和19℃次之,31℃最低;幼虫及蛹存活率在31℃均为0,表明米缟螟不耐高温;卵、幼虫、蛹及未成熟期的发育起点温度分别为13.21、17.12、14.76和16.47℃,有效积温分别为117.94、870.88、149.70和1442.75日·度.研究结果与米缟螟在贵州息烽地区一年发生2至3代的事实大致相符.     

寄主和温度对西花蓟马生长发育的影响

研究了4种豆科寄主植物及5个不同温度处理对西花蓟马生长发育的影响,并对各虫态的发育起点温度和有效积温进行了分析.结果表明:同一温度条件下,西花蓟马取 食不同豆科寄主植物时,各虫态的发育历期差异显著,但不同温度下不同寄主处理间的差异性不同;西花蓟马的未成熟期取食四季豆叶片时发育最快,取食蚕豆叶片时发育最慢,两寄主间存在显著差异;取食同一寄主植物时,不同温度处理下,西花蓟马各虫态的发育历期差异显著,且随温度升高历期缩短,发育速率和温度之间为直线关系;西花蓟马各虫态在不同寄主植物上的发育起点温度和有效积温各不相同,未成熟期取食蚕豆叶片时发育起点温度最低为6.35℃,但需要的有效积温最高为331.36日度.     

外源水杨酸甲酯(MeSA)处理茶树对茶园主要害虫及其天敌的影响

研究了4种豆科寄主植物及5个不同温度处理对西花蓟马生长发育的影响,并对各虫态的发育起点温度和有效积温进行了分析。结果表明:同一温度条件下,西花蓟马取食不同豆科寄主植物时,各虫态的发育历期差异显著,但不同温度下不同寄主处理间的差异性不同;西花蓟马的未成熟期取食四季豆叶片时发育最快,取食蚕豆叶片时发育最慢,两寄主间存在显著差异;取食同一寄主植物时,不同温度处理下,西花蓟马各虫态的发育历期差异显著,且随温度升高历期缩短,发育速率和温度之间为直线关系;西花蓟马各虫态在不同寄主植物上的发育起点温度和有效积温各不相同,未成熟期取食蚕豆叶片时发育起点温度最低为6.35℃,但需要的有效积温最高为331.36日度。     

不同变温组合条件下二点委夜蛾的生长发育

【目的】为明确变温条件对二点委夜蛾Athetis lepigone (Möschler) 实验种群生长发育的影响。【方法】分别设置6个变温组合（20/24℃, 20/28℃, 20/32℃, 24/28℃, 24/32℃和28/32℃）,通过测定和计算各虫态发育起点温度和有效积温及生命表参数来研究变温对二点委夜蛾卵、幼虫、蛹、世代平均发育历期、存活率和繁殖力的影响。【结果】不同变温组合对二点委夜蛾各虫态的发育历期、存活率及种群繁殖力有显著影响。发育历期随着变温组合平均温度的升高而缩短,二点委夜蛾世代存活率由大到小的顺序为24/28℃>20/32℃>28/32℃>20/28℃>24/32℃>20/24℃。24/28℃时产卵量最高,单雌产卵量为390.70粒。世代发育起点温度和有效积温分别为10.37℃和663.17日·度。在不同变温组合下内禀增长率r_m值随着平均温度的升高先上升后降低。在24/28℃时,二点委夜蛾r_m、净增殖率R₀和周限增长率λ最大,种群加倍时间 t 和世代平均周期 T 最小。【结论】24/28℃是二点委夜蛾实验种群生长发育及繁殖的最适变温组合,本研究结果为二点委夜蛾的预测预报及综合防治提供了科学依据。     

温度对棉大卷叶螟生长发育和繁殖的影响

本文利用生命表方法评价了温度对棉大卷叶螟生长发育和繁殖的影响.结果表明：在17 ℃～26 ℃温度范围内,棉大卷叶螟的发育历期随温度升高而显著缩短;当温度超过32 ℃时,其发育历期延长.棉大卷叶螟的世代起点发育温度为12.08 ℃,有效积温为436.2日·度.在17 ℃～35 ℃温度范围内,棉大卷叶螟的存活率在26 ℃下最高,其他温度下的存活率随温度的升高或降低而降低.在17 ℃～35 ℃之间,棉大卷叶螟实验种群的内禀增长率、世代净增殖率、周限增长率分别在29、26和32 ℃下最大,其值分别为0.1268、415.65和1.185.世代平均历期随着温度的升高而缩短,在17 ℃下最长,为89.11 d;在35 ℃下最短,为28.68 d.     

温度对瓜绢螟生长发育和繁殖的影响

【目的】明确不同温度对瓜绢螟Dianphania india (Saunders)生长发育及繁殖的影响,了解其发育起点温度和有效积温,为瓜绢螟的测报及综合治理提供科学依据。【方法】在室内恒温条件下,研究瓜绢螟在不同温度(21、24、27、30和33°C)下的发育历期、发育起点温度、有效积温和生命表参数。【结果】研究表明,温度对瓜绢螟不同发育阶段有显著影响;其中,卵历期(4.52 d)、幼虫历期(25.32 d)、蛹历期(13.98 d)、雌虫寿命(56.44 d)、雄虫寿命(52.79 d)及世代历期(46.15 d)均在21°C条件下为最大值,且随着温度升高有逐渐降低的趋势,在33°C均达到最小值;卵、幼虫、蛹和成虫发育起点温度分别为13.54、9.90、14.28和15.00°C,有效积温分别为38.00、287.00、77.72和277.60日·度;33°C下的内禀增长率r_m和周限增长速率λ最高,分别为0.179 21和1.196 27,但雌虫产卵量在此温度下开始下降;在30°C下净增值率R₀最大(84.212),而总生殖率GRR在27...     

Life history parameters of the cattle long‐nosed sucking louse,Linognathus vituli

Cattle sucking lice, Linognathus vituli (L.) (Phthiraptera: Linognathidae), were obtained from naturally infected cattle and maintained within ‘arenas’ affixed to the backs of cattle confined in controlled environment chambers maintained at a constant temperature of 15 °C. Temperatures measured within the arenas at an ambient temperature of 15 °C were constant at about 34 °C and only slightly above the temperature on nearby skin. The effect of temperature on egg development was determined using a gradient of temperatures between 25 °C and 41 °C. Eggs did not develop at temperatures of < 26 °C or > 39 °C. Survival of eggs was highest at temperatures of 30 °C and 35 °C. The earliest hatch was observed at 5 days post‐oviposition (at 33–35 °C). Development was extended to as long as 13 days at the lower temperatures. Kaplan–Meier survival probabilities were compared for lice kept at two densities in the arenas and showed there to be no effect of density on louse survival. Similarly, the mean number of eggs/louse/day over an 8‐day period was not influenced by louse density.     

Viability of plum ovules at different temperatures

The viability of ovules was studied in five plum cultivars under laboratory conditions at four constant temperatures: 5°C, 10°C, 15°C and 20°C and under field conditions over two years. During 10 days from the onset of full bloom, ovule viability in cvs ‘?a?anska Rana’, ‘?a?anska Najbolja’ and ‘?a?anska Lepotica’ was between 80–100 % at the temperatures of 5°C, 10°C and 15°C, in both years. In the same period, ovule viability in cvs ‘Wangenheims Frühzwetsche’ and ‘Po?ega?a’ was lower, but never below 50%. At the constant temperature of 20°C, all plum cultivars showed a decline in longevity of ovule viability, which was pronounced in cv. ‘?a?anska Rana’. During the 10 days from the onset of full bloom, ovule viability in all five plum cultivars under field conditions showed a high viability, which approximated to the ovule viability of the cultivars at the constant temperatures of 5°C, 10°C and 15°C, in both years. Determination of the longevity of ovule viability in the mentioned plum cultivars is of great importance due to its effect on the effective pollination period and fertilisation success. This paper deals in detail with the interrelations between the temperature effects on ovule viability, pollen tube growth and fertilisation, as well as on fruit setting.     

Effects of thermoperiods on diapause induction in the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae)

Abstract. The effects of thermoperiods on diapause induction in continuous darkness or under a 12 : 12 h LD photoperiod were investigated in the cabbage beetle, Colaphellus bowringi Baly, a typical short‐day species. The diapause response curves both at different constant temperatures and at the thermocycle of format CT x: (24 ? x) h (16 : 28 °C) under continuously dark rearing conditions showed that the incidence of diapause depended mainly on whether or not the mean temperature was ≤20 °C or >20 °C. If the mean temperature was ≤20 °C, all individuals entered diapause; if >20 °C, the incidence of diapause declined gradually with increasing mean temperatures. The thermocycle (CT 12 : 12 h) with a series of different cryophases (8–22 °C) and thermophases (24–32 °C) under continuous darkness demonstrated a cryophase response threshold temperature of approximately 19 °C and a thermophase response threshold temperature of approximately 31 °C. Thermoperiodic amplitude (temperature difference between cryophase and thermophase) was shown to have a significant influence on diapause induction at the mean temperatures of 22, 23 and 24 °C, but not at ≥25 °C. Thermoperiodic responses under LD 12 : 12 h clearly showed that the incidence of diapause was influenced strongly by the photophase temperature. The thermoperiod under LD 12 : 12 h induced a much lower incidence of diapause than the thermoperiod with the same temperature in continuous darkness. The ecological significance of thermoperiodic induction of diapause in this species is discussed.     

Twenty-four-hour variation of vestibular function in young and elderly adults

ABSTRACT

Animal and human studies demonstrate anatomical and functional links between the vestibular nuclei and the circadian timing system. This promotes the hypothesis of a circadian rhythm of vestibular function. The objective of this study was to evaluate the vestibular function through the vestibulo-ocular reflex using a rotatory chair at different times of the day to assess circadian rhythmicity of vestibular function. Two identical studies evaluating temporal variation of the vestibulo-ocular reflex (VOR) were performed, the first in young adults (age: 22.4 ± 1.5 y), and the second in older adults (70.7 ± 4.7 y). The slow phase velocity and time constant of the VOR were evaluated in six separate test sessions, i.e., 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. In both studies, markers of circadian rhythmicity (temperature, fatigue, and sleepiness) displayed expected usual temporal variation. In young adults, the time constant of the VOR showed variation throughout the day (p < .005), being maximum 12:25 h (06:00 h test session) before the acrophase of temperature circadian rhythm. In older adults, the slow phase velocity and time constant also displayed temporal variation (p < .05). Maximum values were recorded at 10:35 h (06:00 h test session) before the acrophase of temperature circadian rhythm. The present study demonstrates that vestibular function is not constant throughout the day. The implication of the temporal variation in vestibular system in equilibrium potentially exposes the elderly, in particular, to differential risk during the 24 h of losing balance and falling.     

The development of milky disease under laboratory and field temperature regimes

The effect of temperature on the development of milky disease agent, Bacillus popilliae var. rhopaea, in third-instar Rhopaea verreauxi larvae was studied in two experiments. In the first experiment, only small differences were found between the probit lines of final percentage infection against dose under five temperature regimes (constant 18, 23, and 28°C; alternating 13–23°C, and 18–28°C). The disease developed more slowly at the lower temperatures while alternating temperatures gave shorter ET₅₀ values than the equivalent constant temperatures. In the second experiment, a higher incidence of disease was obtained under field conditions than under any of the laboratory conditions tested. It was concluded that for up to 6 months/year temperature is not likely to limit the development of B. popilliae var. rhopaea in the field, and that, under field conditions, most larvae would achieve a Phase IV infection.     

Influence of acclimation temperature on GDP-mannose: Dolicholphosphate mannosyltransferase of trout liver (Salmo Gairdneri)

Mannosyltransferase activity has been studied in trout liver microsomes prepared from fish adapted during 1 month at three different temperatures: 7, 15 and 21°C; the purpose of the study was to try and answer this question: is the enzyme sensitive to temperature variations and if so, do optimum pH variations reflect an adaptation to temperature changes? The following effects were observed: 1. Optimum pH values do not vary significantly with incubation temperature; only a discrete shift towards more acidic pH has been observed for trouts raised at 21°C. 2. For trouts raised at 7 and 15°C, the enzymic activity increases slightly with incubation temperature while it remains constant for the trouts acclimated at 21°C. This observation could be explained by a lower level of endogenous dolicholphosphate. 3. At any incubation temperature, the higher the acclimation temperature, the lower the enzymic activity.     

Thermosensitive genetic dwarfs of apple

The role of environment on the dwarfing (short internode) phenomenon of apple (Malus domestisca Borkh.) was investi gated and defined in controlled environmental chambers. Orchard-grown very dwarf, dwarf and semi-dwarf trees obtained by natural sibcrossing of spur-type cv. Golden Delicious and cv. Delicious, as well as standard cv. Golden Delicious, were propagated via in vitro techniques. Growth was rapid and none of the 4 types exhibited dwarf-like characteristics when grown at constant 27°C with 12, 14 or 16 h daylengths. Standard and very dwarf plants grew at nearly the same rate at constant 30°C, whereas growth nearly ceased on both types at constant 35°C after 7 days. Dwarf and very dwarf plants responded differently from standard and semi-dwarf plants when grown under alternating (ramped) night/day temperatures (15 or 20°C night ramped up to a daytime maximum over 8 h of 23, 28, 33 or 38°C, held for 2 h and then ramped down over 5 h to the night temperature). As the night/maximum day temperature differentia) increased from 0 to 23° under the ramping environments, growth of dwarf plants decreased markedly as compared to standard plants. When the same night/maximum day temperature differential occurred, the effect on decreasing shoot length was greater at the higher (20°C) night temperature. Increasing maximum day temperatures under the ramped environment also reduced leaf area plant^?1 but did not markedly affect leaf number, resulting in short internodes. When a period of constant temperature was followed by ramped temperatures or vice versa, the sequence of constant vs ramped environments made little difference in the final growth of the 4 plant types. The data point to high temperature as the major factor for causing dwarfing of the sensitive plant types. Increasing the differential between night and maximum day temperature resulted in short internode. dwarf plants with small leaves similar to orchard-grown dwarf trees.     

Effects of daily fluctuating temperatures on the Drosophila–Leptopilina boulardi parasitoid association

Koinobiont parasitoid insects, which maintain intimate and long-term relationships with their arthropod hosts, constitute an association of ectothermic organisms that is particularly sensitive to temperature variations. Because temperature shows pronounced natural daily fluctuations, we examined if experiments based on a constant temperature range can mask the real effects of the thermal regime on host-parasitoid interactions. The effects of two fluctuating thermal regimes on several developmental parameters of the Drosophila larval parasitoid Leptopilina boulardi were analyzed in this study. Regime 1 included a range of 16–23–16 °C and regime 2 included a range of 16–21–26–21–16 °C (mean temperature 20.1 °C) compared to a 20.1 °C constant temperature. Under an average temperature of 20.1 °C, which corresponds to a cold condition of L. boulardi development, we showed that the success of parasitism is significantly higher under a fluctuating temperature regime than at constant temperature. A fluctuating regime also correlated with a reduced development time of the parasitoids. In contrast, the thermal regime did not affect the ability of Drosophila to resist parasitoid infestation. Finally, we demonstrated that daily temperature fluctuation prevented the entry into diapause for this species, which is normally observed at a constant temperature of 21 °C. Overall, the results reveal that constant temperature experiments can produce misleading results, highlighting the need to study the thermal biology of organisms under fluctuating regimes that reflect natural conditions as closely as possible. This is particularly a major issue in host-parasitoid associations, which constitute a good model to understand the effect of climate warming on interacting species.     

Entrainment of the circadian rhythm in larval release of the crab Dyspanopeus sayi by temperature cycles

Marine and estuarine crabs brood attached eggs, which hatch synchronously releasing larvae at precise times relative to environmental cycles. The subtidal crab Dyspanopeus sayi has a circadian rhythm, in which larvae are released within the 4-h interval after the time of ambient sunset. Previous studies demonstrated that the rhythm can be entrained by the light:dark cycle. Since subtidal crabs are also exposed to temperature fluctuations, an unstudied question was whether the circadian rhythm could be entrained by the diel temperature cycle. To answer this question, ovigerous D. sayi were entrained in darkness to 2.5, 5, and 10 °C temperature cycles that were reverse in phase from the ambient temperature cycle. After entrainment, larval release times were monitored in constant conditions of temperature and darkness with a time-lapse video system. The effectiveness of a temperature cycle to shift the timing of larval release increased as the magnitude of the temperature cycle increased and as crabs were exposed to increasing numbers of entrainment cycles. However, entrainment to a 10 °C cycle only lasted 2 days in constant conditions. When crabs were entrained to a light:dark vs. a 10 °C temperature cycle, the light:dark cycle was dominant for entrainment. Nevertheless, ovigerous crabs do sense temperature cycles and in areas where daylight is too low for entrainment, temperature cycles can be used to regulate the time of larval release.     

EVOLUTIONARY ADAPTATION TO TEMPERATURE II. THERMAL NICHES OF EXPERIMENTAL LINES OF ESCHERICHIA COLI

Groups of replicated lines of the bacterium Escherichia coli were propagated for 2,000 generations at constant 32, 37, or 42°C, or in an environment that alternated between 32 and 42°C. Here, we examine the performance of each group across a temperature range of 12-44°C measuring the temperatures over which each line can maintain itself in serial dilution culture (the thermal niche). Thermal niche was not affected by selection history: average lower and upper limits remained about 19 and 42°C for all groups. In addition, no significant differences among groups were observed in rate of extinction at more extreme temperatures. Within the thermal niche, we measured the mean fitness of the evolved groups relative to their common ancestor. Increases in mean fitness were temperature specific, with the largest increase for each group occurring near its selected temperature. Thus, the temperature at which mean fitness relative to the ancestor was greatest (the thermal optimum) diverged by about 10°C for the groups selected at constant 32°C versus constant 42°C. Tradeoffs in relative fitness (decrements relative to the ancestor elsewhere within the thermal niche) did not necessarily accompany fitness improvements, although tradeoffs were observed for a few of the lines. We conclude that adaptation in this system was quite temperature specific, but substantial divergence among groups in thermal optima had little effect on the limits of their thermal niches and did not necessarily involve tradeoffs in fitness at other temperatures.