Low temperatures play an important role in arthropods because they affect both the individual and population development of all physiological and behavioural activities. Manipulation with low temperatures is a primary nonchemical pest control method. For stored product and food industry practitioners, a knowledge of pest thermal requirements, in particular threshold temperatures at which development and other activities of a particular pest species cease, is of crucial importance. This review presents summary data regarding the lower temperature thresholds of 121 species of stored product and food industry pests from six arthropod taxa (Acari, Coleoptera, Lepidoptera, Psocoptera, Diptera, and Blattodea). In particular, this review collected and summarized information regarding the lower development thresholds, lower population thresholds, lower acoustic or respiratory thresholds, lower walking and flying thresholds and lower trap capture thresholds for flying and walking arthropods. The average lower development threshold (LDT) differed among orders: the lowest was reported for Acari (6.8 °C) and Diptera (8.1 °C), followed by Lepidoptera (11.3 °C) and Psocoptera (13.8 °C), and the highest was reported for Coleoptera (14 °C) and Blattodea (15 °C). An exclusion-function was established showing the percentage of pest species (n = 112) that were developmentally suppressed (excluded) due to temperatures reaching the LDT in the range of decreasing temperatures from 25 °C to 0 °C. We scaled various temperature thresholds from the lowest to highest temperature as follows: the walking threshold, the trap capture threshold for walking insects, the lower development threshold, lower population threshold, lower flying threshold and the lower trap capture threshold for flying pests. Important pest species were identified for which information regarding the lower temperature threshold is missing, or for which the information is too variable and should be refined in future research.

• Keywords
• development, flying, forensic entomology, individual, pest management, populations, respiration, temperature, thresholds, walking,
• Publication type
• Journal Article MeSH
• Review MeSH

Temperature drives development in insects and other ectotherms because their metabolic rate and growth depends directly on thermal conditions. However, relative durations of successive ontogenetic stages often remain nearly constant across a substantial range of temperatures. This pattern, termed 'developmental rate isomorphy' (DRI) in insects, appears to be widespread and reported departures from DRI are generally very small. We show that these conclusions may be due to the caveats hidden in the statistical methods currently used to study DRI. Because the DRI concept is inherently based on proportional data, we propose that Dirichlet regression applied to individual-level data is an appropriate statistical method to critically assess DRI. As a case study we analyze data on five aquatic and four terrestrial insect species. We find that results obtained by Dirichlet regression are consistent with DRI violation in at least eight of the studied species, although standard analysis detects significant departure from DRI in only four of them. Moreover, the departures from DRI detected by Dirichlet regression are consistently much larger than previously reported. The proposed framework can also be used to infer whether observed departures from DRI reflect life history adaptations to size- or stage-dependent effects of varying temperature. Our results indicate that the concept of DRI in insects and other ectotherms should be critically re-evaluated and put in a wider context, including the concept of 'equiproportional development' developed for copepods.

• MeSH
• Models, Biological * MeSH
• Insecta growth & development   MeSH
• Life Cycle Stages * MeSH
• Models, Statistical * MeSH
• Temperature * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

We tested whether two basic thermal requirements for insect development, lower developmental thresholds, i.e. temperatures at which development ceases, and sums of effective temperatures, i.e. numbers of day degrees above the lower developmental thresholds necessary to complete development, differ among insect species that proved to be successful invaders in regions outside their native range and those that did not. Focusing on species traits underlying invasiveness that are related to temperature provides insights into the mechanisms of insect invasions. The screening of thermal requirements thus could improve risk-assessment schemes by incorporating these traits in predictions of potentially invasive insect species. We compared 100 pairs of taxonomically-related species originating from the same continent, one invasive and the other not reported as invasive. Invasive species have higher lower developmental thresholds than those never recorded outside their native ranges. Invasive species also have a lower sum of effective temperatures, though not significantly. However, the differences between invasive and non-invasive species in the two physiological measures were significantly inversely correlated. This result suggests that many species are currently prevented from invading by low temperatures in some parts of the world. Those species that will overcome current climatic constraints in regions outside their native distribution due to climate change could become even more serious future invaders than present-day species, due to their potentially faster development.

• MeSH
• Models, Biological MeSH
• Ecosystem MeSH
• Insecta classification   growth & development   physiology   MeSH
• Climate Change MeSH
• Temperature MeSH
• Introduced Species * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH

Plant species distributions are determined by the response of populations to regional climates; however, little is known about how alien plants that arrive in central Europe from climatically warmer regions cope with the temperature conditions at the early stage of population development. Ambrosia artemisiifolia (common ragweed) is an invasive annual plant causing considerable health and economic problems in Europe. Although climate-based models predict that the whole of the Czech Republic is climatically suitable for this species, it is confined to the warmest regions. To determine the factors possibly responsible for its restricted occurrence, we investigated the effects of temperature and nutrient availability on its seedlings. The plants were cultivated at one of seven temperature regimes ranging from 10 to 34 °C, combined with three nutrient levels. The data on the rate of leaf development were used to calculate the lower developmental threshold (LDT, the temperature, in °C, below which development ceases), the sum of effective temperatures (SET, the amount of heat needed to complete a developmental stage measured in degree days above LDT) and width of the thermal window. The rate of development decreased with decrease in temperature and nutrient supply. Besides this, the decrease in the availability of nutrients resulted in decreased LDT, increased SET and wider thermal window. The dependence of LDT and SET on the availability of nutrients contradicts the concept that thermal constants do not vary. Our results highlight temperature as the main determinant of common ragweed's distribution and identify nutrient availability as a factor that results in the realized niche being smaller than the fundamental niche; both of these need to be taken into account when predicting the future spread of A. artemisiifolia.

• Keywords
• Ambrosia artemisiifolia, common ragweed, invasive species, non-indigenous plants, nutrient limitation, plant nutrition, rate of development, thermal time,
• Publication type
• Journal Article MeSH

UNLABELLED: In exothermal organisms, temperature is an important determinant of the rate of ecophysiological processes, which monotonically increase between the minimum (t d min) and maximum (t d max) temperatures typical for each species. In insects, t d min and t d max are correlated and there is a approximately 20°C interval (thermal window W T = t d max - t d min) between them over which insects can develop. We assumed that other exotherms have similar thermal windows because the thermal kinetics of their physiological processes are similar. In this study, we determined the thermal requirements for germination in plants. Seeds of 125 species of Central European wild herbaceous and crop plants were germinated at nine constant temperatures between 5 and 37°C, and the time to germination of 50% of the seeds D and rate of germination R (=1/D) were determined for each temperature and the Lactin model used to determine t d min, t d max, and W T. The average width of the thermal windows for seeds was significantly wider (mean 24°C, 95% CI 22.7-24.2°C), varied more (between 14.5 and 37.5°C) and development occurred at lower temperatures than recorded for insects. The limiting temperatures for germination, t d min and t d max, were not coupled, so the width of the thermal window increased with both a decrease in t d min and/or increase in t d max. Variation in W T was not associated with taxonomic affiliation, adult longevity, or domestication of the different species, but tends to vary with seed size. Plants are poor at regulating their temperature and cannot move to a more suitable location and as a consequence have to cope with wider ranges in temperatures than insects and possibly do this by having wider thermal windows. SYNTHESIS: The study indicated specificity of W T in different exotherm taxa and/or their development stages.

• Keywords
• Adaptation, domestication, life history, seed size, taxonomic affiliation, thermal window, thermoregulation,
• Publication type
• Journal Article MeSH