SEED GERMINATION STUDIES IN MUSA. II. ALTERNATING TEMPERATURE REQUIREMENT FOR THE GERMINATION OF MUSA BALBISIANA

Stotzky , G., and Elsie A. Cox . (Central Research Labs., United Fruit Co., Norwood, Mass.) Seed germination studies in Musa. II. Alternating temperature requirement for the germination of Musa balbisiana. Amer. Jour. Bot. 49(7): 763–770. Illus. 1962.—Alternating temperatures were found to be required for the germination of seeds of Musa balbisiana. The temperature differentials optimal for germination in soil are dependent upon both the high and low temperatures, and range from 8–23 C. Germination is maximal when the seeds are held 6–12 hr at the high (27–35 C) and 12–18 hr at the low (12–18 C) temperatures. Some germination can be induced by short exposures to alternating temperatures followed by constant high temperatures, but continuous exposure to alternating temperatures is necessary for maximum germination. Excised embryos develop better at constant than at alternating temperatures, showing that the mechanisms affected by alternating temperatures reside elsewhere in the seed. Alternating temperatures are also required for germination of mechanically scarified seeds, although the temperature differentials are less than those necessary for intact seeds, indicating that the action of alternating temperatures is not on the permeability of the integuments.     

ECOTYPIC VARIATION IN CYSTOCLONIUM PURPUREUM (RHODOPHYTA) SYNCHRONIZES LIFE HISTORY EVENTS IN DIFFERENT REGIONS1

Temperature and daylength responses were determined in culture for isolates of the red alga Cystoclonium purpureum (Hudson) Batters from Nova Scotia (NS, Canada), Helgoland (HE, Germany), and Roscoff (RO, France). Most isolates survived temperatures of –1.5°/–2° to 23°C, whereas 25°C was lethal. Only the RO-gametophytes died at 23°C. Optimal growth conditions were 10°–20°C in both long and short days for the NS isolates and 8°–15°C and 8°–18°C at daylengths of >12 h for the RO and HE isolates, respectively. Tetrasporophytes and gametophytes of the NS isolate reproduced at 10°–20°C in long and short days within 5 months. At lower temperatures reproduction was limited or slow. The European isolates formed tetrasporangia at 10°–20°C (HE) or 5°–l8°C(RO), spermatangia at 5°–15°C (HE) or 5°–20°C (RO), and carpospores at 5°–15°C(HE) or 10°–15°C (RO). Short days either blocked or delayed reproduction of the European isolates. The phenology of C. purpureum was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. In early spring, growth was rapid and plants started to form reproductive structures. In summer, tetra-and carpospores were shed followed by degeneration of the upright axes while branched holdfasts persisted. New upright axes and juvenile plants were formed in autumn, but these remained small during the winter months. Published data indicate that the seasonal pattern at Nova Scotia is similar, although the onset of growth and reproduction is delayed until the end of spring. These observations correspond well with the results of the experiments. The life history of C. purpureum is regulated by temperature and daylength. In the eastern Atlantic, the limiting effect of short days confines growth and reproduction to spring and summer. In the western Atlantic, low winter temperatures alone bring about the same seasonal pattern. After plants have reproduced, uprights degenerate in spite of continuing favorable conditions.     

Effect of latitude and acclimation on the lethal temperatures of the peach‐potato aphid Myzus persicae

• 1 Aphids, similar to all insects, are ectothermic and, consequently, are greatly affected by environmental conditions. The peach potato aphid Myzus persicae (Sulzer) has a global distribution, although it is not known whether populations display regional adaptations to distinct climatic zones along its distribution and vary in their ability to withstand and acclimate to temperature extremes. In the present study, lethal temperatures were measured in nine anholocyclic clones of M. persicae collected along a latitudinal cline of its European distribution from Sweden to Spain. The effects of collection origin and intra‐ and intergenerational acclimation on cold and heat tolerance, as determined by upper and lower lethal temperatures (ULT₅₀ and LLT₅₀, respectively), were investigated.
• 2 Lethal temperatures of M. persicae were shown to be plastic and could be altered after acclimation over just one generation. Lower lethal temperatures were significantly depressed in eight of nine clones after acclimation for one generation at 10°C (range: ?13.3 to ?16.2°C) and raised after acclimation at 25°C (range: ?10.7 to ?11.6°C) compared with constant 20°C (range: ?11.9 to ?12.9°C). Upper lethal temperatures were less plastic, although significantly increased after one generation at 25°C (range: 41.8–42.4°C) and in five of nine clones after acclimation at 10°C. There was no evidence of intergenerational acclimation over three generations.
• 3 Thermal tolerance ranges were expanded after acclimation at 10 and 25°C compared with constant 20°C, resulting in aphids reared at 10°C surviving over a temperature range that was approximately 2–6°C greater than those reared at 25°C.
• 4 There was no clear relationship between lethal temperatures and latitude. Large scale mixing of clones may occur across Europe, thus limiting local adaption in thermal tolerance. Clonal type, as identified by microsatellite analysis, did show a relationship with thermal tolerance, notably with Type O clones being the most thermal tolerant. Clonal types may respond independently to climate change, affecting the relative proportions of clones within populations, with consequent implications for biodiversity and agriculture.

     

Membrane alterations in winter rye and Brassica napus cells during lethal freezing and plasmolysis

Abstract Cells fixed during freezing or plasmolysis were used to study membrane alterations in hardened and non-hardened Brassica napus suspension-cultured cells and rye leaf mesophyll cells. The plasmalemma in non-hardened rye mesophyll cells formed multilamellar vesicles during lethal freezing at high subzero temperatures (–5°C). These vesicles became highly condensed at lower subzero temperatures (–10°C). Conversely, cold-hardened rye mesophyll cells did not undergo membrane alterations at these temperatures. The results from plasmolysis of B. napus and rye mesophyll cells hardened by ABA at 25 °C and low temperature (2°C), respectively, verify the cell response to lethal freezing. Again there was a continuum of responses with 1 kmol m^?3 balanced salt causing multilamellar protrusions. Appression of the plasmalemma against the tonoplast to form multilamellar vesicles and the invagination of these vesicles into the tonoplast were also observed in rye cells undergoing lethal plasmolysis. Increasing the plasmolysing solution to 3 kmol m^?3 occasionally caused the formation of multilamellar vesicles on the cell surface of hardened rye mesophyll cells.     

INTERSPECIFIC INCOMPATIBILITY IN GOSSYPIUM. II. LIGHT AND ELECTRON MICROSCOPE STUDIES OF CELL NECROSIS AND TUMORIGENESIS IN HYBRIDS OF G. KLOTZSCHIANUM

Many Gossypium interspecific hybrids that involve G. klotzschianum result in either embryo or seedling lethals. Histologically, lethal symptoms are characterized by necrotic cells and tumors that appear 10–15 days after fertilization in the embryo lethals and at the first true-leaf stage in the seedling lethals. Ultrastructural studies of cell necrosis in seedling lethals show that the first subcellular abnormality is the degeneration of the inner membrane and cristae of the mitochondria. Mitochondrial degeneration is essentially complete before other organelles show evidence of structural aberrations.     

Temperature Tolerances and Geographic Distribution of Three Species of Caridina (Decapoda,Atyidae) in Sri Lanka

The biokinetic zones of C. fernandoi, C. simoni and C. pristis were found to be 15–29 °C, 15–27 °C and 13–27 °C respectively, while their respective ranges of distribution were found to be in altitudes of 0–700, 0–700 and 450–850 m. Their responses to low temperatures indicate that all three species are unlikely to occur above 1,000 m. The lower limit of distribution of C. fernandoi and C. simoni extends to altitudes in which the temperature rises above their ultimate upper incipient lethal temperatures (UILT). They appear to avoid high temperatures by moving into cooler waters. C. pristis cannot do so since it lives in very shallow streams; the lower level of its distribution appears therefore to be limited by its UILT.     

Thermal ecotypes of amphi-Atlantic algae. I. Algae of Arctic to cold-temperate distribution (Chaetomorpha melagonium,Devaleraea ramentacea andPhycodrys rubens)

Three species of Arctic to cold-temperate amphi-Atlantic algae, all occurring also in the North Pacific, were tested for growth and/or survival at temperatures of −20 to 30°C. When isolates from both western and eastern Atlantic shores were tested side-by-side, it was found that thermal ecotypes may occur in such Arctic algae.Chaetomorpha melagonium was the most eurythermal of the 3 species. Isolates of this alga were alike in temperature tolerance and growth rate but Icelandic plants were more sensitive to the lethal temperature of 25°C than were more southerly isolates from both east and west. With regard toDevaleraea ramentacea, one Canadian isolate grew extraordinarily well at −2 and 0°C, and all tolerated temperatures 2–3°C higher than the lethal limit (18–20°C) of isolates from Europe. ConcerningPhycodrys rubens, both eastern and western isolates died at 20°C but European plants tolerated the lethal high temperature longer, were more sensitive to freezing, and attained more rapid growth at optimal temperatures. The intertidal species,C. melagonium andD. ramentacea, both survived freezing at −5 and −20°C, at least for short time periods.C. melagonium was more susceptible thanD. ramentacea to desiccation. Patterns of thermal tolerance may provide insight into the evolutionary history of seaweed species.     

GERMINATION ECOLOGY OF PHACELIA DUBIA VAR. DUBIA IN TENNESSEE GLADES

The germination characteristics of a population of the winter annual Phacelia dubia (L.) Trel. var. dubia from the middle Tennessee cedar glades were investigated in an attempt to define the factor(s) regulating germination in nature. Factors considered were changes in physiological response of the seeds (after-ripening), temperature, age, light and darkness, and soil moisture. At seed dispersal (late May to early June), approximately 50 % of the seeds were non-dormant but, would germinate only at low temperatures (10–15 C). As the seeds aged from June to September, there was an increase in rate and total percent of germination at 10, 15, and 20 C, and the maximum temperature for germination increased to 25 C. Little or no germination occurred at the June, July, and August temperatures in 0- to 2-month-old seeds, even in seeds on soil that was kept continuously moist during this 3-month period. At the September, October, and November temperatures 3- to 5-month-old seeds germinated to high percentages. In all experiments seeds germinated better at a 14-hr photoperiod than in constant darkness. Inability of 0- to 2-month-old seeds to germinate at high summer temperatures allows P. dubia dubia to pass the dry summer in the seed stage, while increase in optimum and maximum temperatures for germination during the summer permits seeds to germinate in late summer and early fall when conditions are favorable for seedling survival and eventual maturation.     

Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana,Phaeophyceae)

Warming ocean temperatures have been linked to kelp forest declines worldwide, and elevated temperatures can act synergistically with other local stressors to exacerbate kelp loss. The bull kelp Nereocystis luetkeana is the primary canopy-forming kelp species in the Salish Sea, where it is declining in areas with elevated summer water temperatures and low nutrient concentrations. To determine the interactive effects of these two stressors on microscopic stages of N. luetkeana, we cultured gametophytes and microscopic sporophytes from seven different Salish Sea populations across seven different temperatures (10–22°C) and two nitrogen concentrations. The thermal tolerance of microscopic gametophytes and sporophytes was similar across populations, and high temperatures were more stressful than low nitrogen levels. Additional nitrogen did not improve gametophyte or sporophyte survival at high temperatures. Gametophyte densities were highest between 10 and 16°C and declined sharply at 18°C, and temperatures of 20 and 22°C were lethal. The window for successful sporophyte production was narrower, peaking at 10–14°C. Across all populations, the warmest temperature at which sporophytes were produced was 16 or 18°C, but sporophyte densities were 78% lower at 16°C and 95% lower at 18°C compared to cooler temperatures. In the field, bottom temperatures revealed that the thermal limits of gametophyte growth (18°C) and sporophyte production (16–18°C) were reached during the summer at multiple sites. Prolonged exposure of bull kelp gametophytes to temperatures of 16°C and above could limit reproduction, and therefore recruitment, of adult kelp sporophytes.     

EVOLUTIONARY ADAPTATION TO TEMPERATURE. VII. EXTENSION OF THE UPPER THERMAL LIMIT OF ESCHERICHIA COLI

What factors influence the ability of populations to adapt to extreme environments that lie outside their current tolerance limits? We investigated this question by exposing experimental populations of the bacterium Escherichia coli to lethally high temperatures. We asked: (1) whether we could obtain thermotolerant mutants with an extended upper thermal limit by this selective screen; (2) whether the propensity to obtain thermotolerant mutants depended on the prior selective history of the progenitor genotypes; and (3) how the fitness properties of these mutants compared to those of their progenitors within the ancestral thermal niche. Specifically, we subjected 15 independent populations founded from each of six progenitors to 44°C; all of the progenitors had upper thermal limits between about 40°C and 42°C. Two of the progenitors were from populations that had previously adapted to 32°C, two were from populations adapted to 37°C, and two were from populations adapted to 41–42°C. All 90 populations were screened for mutants that could survive and grow at 44°C. We obtained three thermotolerant mutants, all derived from progenitors previously adapted to 41–42°C. In an earlier study, we serendipitously found one other thermotolerant mutant derived from a population that had previously adapted to 32°C. Thus, prior selection at an elevated but nonlethal temperature may predispose organisms to evolve more extreme thermotolerance, but this is not an absolute requirement. It is evidently possible to obtain mutants that tolerate more extreme temperatures, so why did they not become prevalent during prior selection at 41–42°C, near the upper limit of the thermal niche? To address this question, we measured the fitness of the thermotolerant mutants at high temperatures just within the ancestral niche. None of the four thermotolerant mutants had an advantage relative to their progenitor even very near the upper limit of the thermal niche; in fact, all of the mutants showed a noticeable loss of fitness around 41°C. Thus, the genetic adaptations that improve competitive fitness at high but nonlethal temperatures are distinct from those that permit tolerance of otherwise lethal temperatures.     

Temperature and salinity tolerances of larval Californian grunion, Leuresthes tenuis (Ayres): A comparison with gulf grunion, L. Sardina (Jenkins & Evermann)

Temperature and salinity tolerances were determined for larval California grunion, Leuresthes tenuis (Ayres), and compared with previous data for Gulf of California grunion, L. sardina (Jenkins & Evermann). Larvae of similar age and acclimation history showed little interspecific difference in thermal tolerance, as measured by half-hour LT₅₀ values for 20–30 day old late postlarvae acclimated at various temperatures, and by upper and lower incipient lethal temperatures for 18°C-acclimated prolarvae. The upper incipient lethal temperature differed by 1 deg.-C (32°C for L. tenuis, 31°C for L. sardina), while the lower incipient lethal temperature for the 18°C acclimated prolarvae of both species was 7.5°C. L. tenuis larvae were much less euryhaline than L. sardina, with incipient lethal salinities of 4.2–41 %. for prolarvae and 8.6–38 %. for 20-day-old postlarvae; comparable values for L. sardina are 4–67.5 %. and 5–57.5 %. Both species show a decrease in temperature and salinity tolerance with age. The larvae of these disjunct congeners show a significant physiological divergence in euryhalinity but not in overall temperature tolerance. These tolerances are discussed in relation to the respective geographic ranges and behavioral responses of the two species.     

EXPERIMENTAL CONTROL OF FLOWERING IN LEMNA. II. SOME EFFECTS OF MEDIUM COMPOSITION,CHELATING AGENTS AND HIGH TEMPERATURES ON FLOWERING IN L. PERPUSILLA 6746

Hillman , William S. (Yale U., New Haven, Conn.) Experimental control of flowering in Lemna. II. Some effects of medium composition, chelating agents and high temperatures on flowering in L. perpusilla 6746. Amer. Jour. Bot. 46(7): 489–495. Illus. 1959.—-L. perpusilla 6746 flowers as a short-day plant on Hutner's medium (containing ethylenediaminetetraacetic acid [EDTA]) at constant temperatures from 25 to 30°C., but eventually flowers also in old cultures under 16 or 24 hr. of light. This old-culture flowering is more pronounced in dilute medium. Flowering is rapid under both long and short days at constant temperatures from 25 to 28°C. in media not containing EDTA; the addition of 10^-5 M EDTA or of similar or higher concentrations of numerous other chelating agents suppresses flowering under long days but not under short (8 hr. light). This effect does not depend on promotion or inhibition of vegetative growth. At 29 to 30°C., a short-day requirement is manifested even in media permitting flowering under long days at the lower temperatures. Temperatures above 31°C. completely inhibit flowering under all conditions. Brief periods of high temperature given to plants under short-day conditions inhibit flowering when given during the dark period but not during the light period. The implications of these observations for the further study of flowering are discussed.     

UNIALGAL CULTURES OF CLADOPHORA GLOMERATA (L.) KÜTZ.12

Unialgal cultures of Cladophora glomerata (L.) Kütz. grew with increasing vigor at temperatures between 15 and 30 C. Vegetative cells were killed upon freezing or when exposed to temperatures above 30 C. No growth occurred at 5 C and only slight growth was observed at 10 C. Effects of near lethal temperature on C. glomerata were dependent upon the duration of exposure in addition to the actual temperature attained. The response of this alga to various temperatures under culture conditions is in accord with tolerance limits established for naturally occurring populations. It seems probable that the annual periodicity of C. glomerata is regulated in large measure by seasonal variations in water temperature, greatest abundance coinciding with water temperatures between 15 and 30 C.     

Soil temperatures during bushfires in semi-arid,mallee shrublands

Abstract Soil temperatures were measured during 11 experimental fires in semi-arid mallee shrublands in central NSW. Sensors were placed at depths from 1–10 cm beneath the soil surface in three fuel types; litter beneath Eucalyptus shrubs, live hummocks of the grass Triodia irritans and litter beneath shrubs of Acacia species. Weights of these fuels per unit area were determined. Maximum soil temperature and its duration were related to fuel type and depth. Mean weights of Eucalyptus and Triodia fuels were similar (0.35 kg m^?2), while there was less Acacia fuel (0.1 kg m^?2). Highest maximum temperatures were registered under Eucalyptus litter (e.g. 140°C at 2 cm). Maximum temperatures under Triodia and Acacia litter were similar (e.g. 60–70°C at 2 cm). Durations were examined in two temperature classes (60–120 and > 120°C) chosen to represent threshold for stimulation of germination and mortality, respectively, of soil-stored seeds. Temperatures between 60 and 120°C were recorded only between 0–2 cm soil depth for Acacia and Triodia (one exception at 4 cm). No temperatures >120°C were recorded for these fuel types. Temperatures between 60 and 120°C were recorded to 5 cm depth under Eucalyptus fuels while putative lethal temperatures for seeds occurred occasionally at 0–2 cm depth. The results indicated greatest potential for stimulation of germination and death of buried seeds under Eucalyptus fuels, although the level of variability of temperature was highest under Eucalyptus fuels. Despite similar fuel loads, differences between temperatures under Eucalyptus and Triodia fuels reflected the influence of the depth of the fuel bed, with Triodia hummocks constituting a deep fuel bed and Eucalyptus litter a shallow fuel bed.     

Heat stress reduced survival but sped up development in Heliconius erato butterflies

Anthropogenic climate change is thought to present a significant threat to biodiversity, in particular to tropical ectotherms, and the effects of long-term developmental heat stress on this group have received relatively little research attention. Here, we studied the effects of experimentally raising developmental temperatures on a tropical butterfly. We measured survival, development time, adult body mass and wing size of Heliconius erato demophoon (Linnaeus) (Lepidoptera: Nymphalidae) across three temperature treatments. Egg survival was lower in the hotter treatments, with 84%, 73% and 49% of eggs hatching in the 20–30°C (fluctuating temperature with 12 h at 20°C followed by 12 h at 30°C), 23–33°C and 26–36°C treatments, respectively. Larval survival was three times lower in the 26–36°C treatment (8%) compared with the 20–30°C treatment (26%), and we did not detect differences in pupal survival across treatments due to high mortality in earlier stages. Under a moderately increased temperature at 23–33°C, larvae developed faster and adults had a higher body mass and wing loading, but this was not seen in the hottest treatment (26–36°C). Females were also heavier than males in the 23–33°C treatment, but there was no associated increase in wing size. This may suggest a different developmental response to moderately elevated temperatures between the sexes. In summary, high developmental temperatures are particularly lethal for eggs and less so for larvae and also affect adult morphology. This highlights the importance of understanding the effects of temperature variation across ontogeny in tropical ectotherms.     

Effects of temperature on the growth and survival of the European eel, Anguilla anguilla L.

Experiments to determine the growth rate of eels ( Anguilla anguilla L.) at different temperatures are described and show the optimum temperature for growth to be 22–23° C. The ultimate upper lethal temperature was found to be 38° C and the critical thermal maximum varied from 33 to 39° C for fish acclimated at 14 to 29° C. An attempt was also made to determine lower lethal temperatures. Eels enter a state of torpor at temperatures varying from 3° C for fish acclimated at 29° C to less than 1° C for fish acclimated at 23° C or below. The results have been used to estimate the growth rates expected from eels cultured in power station cooling water using different types of temperature control.     

Heat effects on seeds and rhizomes of a selection of boreal forest plants and potential reaction to fire

To analyse the potential reaction to firegenerated heat pulses, seeds of 12 species of plants and rhizomes of three species were exposed to elevated temperatures for 10 min. The tested material split into three groups with respect to heat tolerance: (1) the rhizomes, for which the lethal temperatures were in the range 55–59° C; (2) the seeds of most of the species tested, for which the lethal temperatures were in the range 65–75° C; (3) The seeds of two species of Leguminosae and three species of Geranium for which the lethal temperatures were around 100° C. For all three Geranium species and for one of the legume species, Anthyllis vulneraria, exposure temperatures above ca. 45° C resulted in dormancy release, and maximum germination occurred above 60–65° C. Speed of germination was little affected for most species, except after exposure to nearlethal temperatures, where it slowed down dramatically, although the seedlings emerging were healthy. We conclude that due to sharp temperature gradients in the soil during fire, differences in heat tolerance between species in most cases are not large enough to be a decisive factor in their post-fire colonising success. There are exceptions: the seeds of certain taxa that are impermeable to water in the dormant state, some of which have heat triggered germination.     

The critical thermal limits for the stone loach, Noemacheilus barbatulus, from three populations in north-west England

1. The chief objective was to determine the upper and lower thermal limits for feeding and survival in the stone loach, Noemacheilus barbatulus, using juveniles (total length 30–45 mm, live weight 0.25–0.80 g) from one population and adults (total length 77–100 mm, live weight 3.6–7.9 g) from three populations. 2. Fish were acclimatized to constant temperatures of 3, 7, 10, 15, 20, 25 and 27°C; then the temperature was changed at a rate of 1°C/30min to determine the critical limits for feeding, survival over 7 days (incipient lethal temperature), or survival for 10 min or less (ultimate lethal temperature). The rate of 1°C/30min was the optimum value from preliminary experiments, using nine rates from 0.5°C/48h to 18°Ch^?1. As values for adults were not significantly different between populations, they were pooled to provide arithmetic means (with 95% CL) for the thermal limits at each acclimation temperature. 3. Feeding limits increased with acclimation temperature to upper and lower mean values of 28.0 ± 0.15°C and 5.1 ± 0.55°C for adults, 25.0 ± 0.54°C and 6.1 ± 0.92°C for juveniles. Incipient lethal levels defined a tolerance zone within which stone loach survive for a considerable time; upper limits increased with acclimation temperature to reach a maximum plateau of 29.1 ± 0.18°C for adults and 29.0 ± 0.40°C for juveniles; lower limits also increased from near 0°C to 3.0 ± 0.40°C for adults and juveniles. Upper limits for the ultimate lethal level increased with acclimation temperature to a maximum plateau of 33.5°C for adults (95% CL ± 0.19) and juveniles (95% CL ± 0.40), whilst the lower limits increased from near 0°C to 2.5 ± 0.30°C. At acclimation temperatures below 20°C, upper incipient and ultimate lethal values were significantly lower for juveniles than those for adults. 4. The thermal tolerance of stone loach was higher than that of juvenile Atlantic salmon or brown trout, one or both of these species often being dominant in streams with stone loach.     

TEMPERATURE RESPONSES AND EVOLUTION OF THERMAL TRAITS IN CLADOPHOROPSIS MEMBRANACEA (SIPHONOCLADALES,CHLOROPHYTA)1

Temperature tolerances and relative growth rates were determined for different isolates of the tropical to warm temperate seaweed species Cladophoropsis membranacea (C. Agardh) Boergesen (Siphonodadales, Chlorophyta) and some related taxa. Most isolates of C membranacea survived undamaged at 18° C for at least 8 weeks. Lower temperatures (5°–15°C) were tolerated for shorter periods of time but caused damage to cells. All isolates survived temperatures up to 34° C, whereas isolates from the eastern Mediterranean and Red Sea survived higher temperatures up to 36°C. Growth occurred between 18° and 32° C, but an isolate from the Red Sea had an extended growth range, reaching its maximum at 35°C. Struvea anastomosans (Harvey) Piccone & Grunow, Cladophoropsis sundanensis Reinbold, and an isolate of C. membranacea from Hawaii were slightly less cold- tolerant, with damage occurring at 18°C. Upper survival temperatures were between 32° and 36° C in these taxa. Temperature response data were mapped onto a phylogenetic tree. Tolerance for low temperatures appears to be a derived character state that supports the hypothesis that C. membranacea originated from a strictly tropical ancestor. Isolates from the Canary Islands, which is near the northern limit of distribution, are ill adapted to local temperature regimes. Isolates from the eastern Mediterranean and Red Sea show some adaptation to local temperature stress. They are isolated from those in the eastern Atlantic by a thermal barrier at the entrance of the Mediterranean.     

Temperature-dependent development,cold tolerance,and potential distribution of Gratiana boliviana (Coleoptera: Chrysomelidae), a biological control agent of tropical soda apple,Solanum viarum (Solanaceae)

The leaf beetle Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) was introduced from South America into the southeastern United States in 2003 as a classical biological control agent of tropical soda apple, Solanum viarum Dunal (Solanaceae). Temperature-dependent development and survival studies revealed that development was completed at temperatures >16°C and ≤34°C. The number of degree-days required to complete one generation was 341 and the estimated lower developmental threshold was 13.37°C. Using nonlinear regression, the upper lethal threshold was estimated to be 34–35°C. Cold tolerance studies revealed that the lethal time for 90% of adults (LT₉₀) was 12.6 days at 5°C and 8.68 days at 0°C. Based on the developmental and cold tolerance data, a map predicting the areas of establishment and number of generations per year was generated, which suggests that the northern extent of the G. boliviana range in the USA will be near 32–33° north latitude. Fewer generations per year in more northern areas of the southeastern USA may decrease the effectiveness of this biological control agent.