Are tropical forests approaching critical temperature thresholds?

There is growing concern about the fate of tropical forests in the face of rising global temperatures. Doughty et al. (2023) suggest that an increase in air temperature beyond ∼4 °C will result in massive death of tropical forest leaves and potentially tree death. However, this prediction relies on assumptions that likely underestimate the heat tolerance of tropical leaves.

Estimation of the Postmortem Interval Through the Use of Development Time of Two South American Species of Forensic Importance of the Genus Lucilia (Diptera: Calliphoridae).

Obtaining the specific development time of each species of forensic interest is crucial for the estimation of an accurate and reliable Minimum Postmortem Interval (PMImin). In Argentina, Lucilia ochricornis (Wiedemann) and Lucilia purpurascens (Walker) (Diptera: Calliphoridae) were masked under the name Lucilia cluvia (Walker) for a long time still in forensic expertise. For this reason, the objective of this work is to deepen the study of the development time of these species and utilize this relevant information in the generation of different associated methods that can be used in forensics to estimate the PMI. Immature stages of L. ochricornis and L. purpurascens were reared in a brood chamber according to the following temperature treatments: 13.4, 15.1, 22.3, and 23.6°C. The development time of each stage/state of these flies was recorded as well as the resulting accumulated degree-hours (ADH), to build isomorphen diagrams and thermal summation models for each species. The development time and ADH were different between both species and their development stages. On the other hand, the methods provided for estimating PMImin provide the forensic entomologist more tools to reach accurate and reliable estimates.

Winter climate change and the poleward range expansion of a tropical invasive tree (Brazilian pepper-Schinus terebinthifolius).

Winter climate change is expected to lead to the tropicalization of temperate ecosystems, where tropical species expand poleward in response to a decrease in the intensity and duration of winter temperature extremes (i.e., freeze events). In the southeastern United States, freezing temperatures control the northern range limits of many invasive nonnative species. Here, we examine the influence of freezing temperatures and winter climate change on the northern range limits of an invasive nonnative tree-Schinus terebinthifolius (Brazilian pepper). Since introduction in the 1800s, Brazilian pepper has invaded ecosystems throughout south and central Florida to become the state's most widespread nonnative plant species. Although Brazilian pepper is sensitive to freezing temperatures, temperature controls on its northern distribution have not been adequately quantified. We used temperature and plant occurrence data to quantify the sensitivity of Brazilian pepper to freezing temperatures. Then, we examined the potential for range expansion under three alternative future climate scenarios (+2°C, +4°C, and +6°C). Our analyses identify a strong nonlinear sigmoidal relationship between minimum temperature and Brazilian pepper presence, with a discrete threshold temperature occurring near -11°C. Our future scenario analyses indicate that, in response to warming winter temperatures, Brazilian pepper is expected to expand northward and transform ecosystems in north Florida and across much of the Gulf of Mexico and south Atlantic coasts of the United States. These results underscore the importance of early detection and rapid response efforts to identify and manage the northward invasion of Brazilian pepper in response to climate change. Looking more broadly, our work highlights the need to anticipate and prepare for the tropicalization of temperate ecosystems by tropical invasive species.

Rainfall, not soil temperature, will limit the seed germination of dry forest species with climate change.

Drylands are predicted to become more arid and saline due to increasing global temperature and drought. Although species from the Caatinga, a Brazilian tropical dry forest, are tolerant to these conditions, the capacity for germination to withstand extreme soil temperature and water deficit associated with climate change remains to be quantified. We aimed to evaluate how germination will be affected under future climate change scenarios of limited water and increased temperature. Seeds of three species were germinated at different temperatures and osmotic potentials. Thermal time and hydrotime model parameters were established and thresholds for germination calculated. Germination performance in 2055 was predicted, by combining temperature and osmotic/salt stress thresholds, considering soil temperature and moisture following rainfall events. The most pessimistic climate scenario predicts an increase of 3.9 °C in soil temperature and 30% decrease in rainfall. Under this scenario, soil temperature is never lower than the minimum and seldomly higher than maximum temperature thresholds for germination. As long as the soil moisture (0.139 cm3 cm3) requirements are met, germination can be achieved in 1 day. According to the base water potential and soil characteristics, the minimum weekly rainfall for germination is estimated to be 17.5 mm. Currently, the required minimum rainfall occurs in 14 weeks of the year but will be reduced to 4 weeks by 2055. This may not be sufficient for seedling recruitment of some species in the natural environment. Thus, in future climate scenarios, rainfall rather than temperature will be extremely limiting for seed germination.

Effect of Temperature Thresholds on Modeled Aedes aegypti (Diptera: Culicidae) Population Dynamics.

Dynamic simulation models provide vector abundance estimates using only meteorological data. However, model outcomes may heavily depend on the assumptions used to parameterize them. We conducted a sensitivity analysis for a model of Aedes aegypti (L.) abundance using weather data from two locations where this vector is established, La Margarita, Puerto Rico and Tucson, Arizona. We tested the effect of simplifying temperature-dependent development and mortality rates and of changing development and mortality thresholds as compared with baselines estimated using biophysical models. The simplified development and mortality rates had limited effect on abundance estimates in either location. However, in Tucson, where the vector is established but has not transmitted viruses, a difference of 5 °C resulted in populations either surviving or collapsing in the hot Arizona mid-summer, depending on the temperature thresholds. We find three important implications of the observed sensitivity to temperature thresholds. First, this analysis indicates the need for better estimates of the temperature tolerance thresholds to refine entomologic risk mapping for disease vectors. Second, our results highlight the importance of extreme temperatures on vector survival at the marginal areas of this vector's distribution. Finally, the model suggests that adaptation to warmer temperatures may shift regions of pathogen transmission.

Reliability of Degree-Day Models to Predict the Development Time of Plutella xylostella (L.) under Field Conditions.

The diamondback moth, Plutella xylostella (L.), is a cosmopolitan pest of brassicaceous crops occurring in regions with highly distinct climate conditions. Several studies have investigated the relationship between temperature and P. xylostella development rate, providing degree-day models for populations from different geographical regions. However, there are no data available to date to demonstrate the suitability of such models to make reliable projections on the development time for this species in field conditions. In the present study, 19 models available in the literature were tested regarding their ability to accurately predict the development time of two cohorts of P. xylostella under field conditions. Only 11 out of the 19 models tested accurately predicted the development time for the first cohort of P. xylostella, but only seven for the second cohort. Five models correctly predicted the development time for both cohorts evaluated. Our data demonstrate that the accuracy of the models available for P. xylostella varies widely and therefore should be used with caution for pest management purposes.

Temperature-dependent development of two neotropical parasitoids of Liriomyza sativae (Diptera: Agromyzidae).

We studied two species of neotropical parasitoids that occur naturally in northeastern Brazil and are associated with Liriomyza sativae (Blanchard): Opius (Gastrosema) scabriventris Nixon (Hymenoptera: Braconidae) and Chrysocharis vonones (Walker) (Hymenoptera: Eulophidae). We evaluated the influence of seven temperatures on the duration of the egg-adult period and on the survivorship of the immature stages of the parasitoids. A temperature increase from 15 to 30°C shortened the egg-adult period of O. scabriventris and C. vonones. However, at 32°C, the developmental time for the braconid was prolonged, and no difference was observed for the eulophid, compared with 30°C. The highest temperature, 35°C, proved to be lethal for both species. At 15°C, C. vonones pupal survivorship was drastically reduced, whereas that of O. scabriventris was unaffected. At most temperatures, the eulophid had an egg-adult period shorter than or similar to the braconid, except at 15°C. The threshold temperature (Tt) of the egg-adult period for O. scabriventris was 7.3°C with a thermal constant (K) of 257.1 degree days (DD). For C. vonones the Tt was 7.4°C for the total cycle and 6.2°C for the pupal stage, with a thermal constant of 246.3 and 140.3 DD, respectively. These data allow an estimate of 29.4 annual generations for O. scabriventris and 30.5 for C. vonones in a melon production region in northeastern Brazil, values that are equivalent to 4.9 and 6.0 more generations than the host. These results demonstrate that both species have potential for application in biological control programs against the leafminer fly L. sativae.

Eclosion rate, development and survivorship of Aedes albopictus (Skuse)(Diptera: Culicidae) under different water temperatures

In tropical areas, where vector insects populations are particularly numerous, temperature usually range between 25°C and 35°C. Considering the importance of such temperature variation in determining mosquitoes population dynamics, in this work the developmental, eclosion and survival rates of the immature stages of Aedes albopictus (Skuse) were compared under constant 25, 30 and 35°C (using acclimatized chambers) and environmental (25°C to 29°C) temperatures. The hatching rate was considered as total number of larvae recovered after 24h. The development period as well as larval and pupal survival rate were evaluated daily. Eclosion rate was significantly higher under environmental temperature than under the studied constant temperatures, suggesting that temperature variation may be an eclosion-stimulating factor. The mean eclosion time increased with the temperature, ranging from 2.8h (25°C) to 5.2h (35°C). The larval period was greatly variable inside each group, although it did not differ significantly amongst groups (11.0 ± 4.19 days), with individuals showing longer larval stages in water at 35°C (12.0 ± 4.95 days) and environmental temperature (13.6 ± 5.98 days). Oppositely, survival was strongly affected by the higher temperature, where only one individual lived through to adult phase. The results suggest that population of Ae. albopictus from Recife may be adapting to increasing of environmental temperatures and that the limiting temperature to larval development is around 35°C.

Em áreas tropicais, onde as populações de insetos vetores são particularmente abundantes, as temperatura usualmente variam entre 25°C e 35°C. Considerando a importância dessa variação na determinação da dinâmica populacional de mosquitos, neste trabalho, desenvolvimento e as taxas de eclosão e sobrevivência dos estágios imaturos de Aedes albopictus (Skuse) foram comparados sob temperaturas constantes de 25, 30 e 35°C (em câmaras climatizadas) e ambientes (25°C a 29°C). A taxa de eclosão foi considerada como o total de larvas obtidas após 24h. O período de desenvolvimento, assim como a taxa de sobrevivência larval e pupal foram avaliados diariamente. A taxa de eclosão foi significativamente mais elevada sob temperatura ambiente comparada às constantes, sugerindo que a variação da temperatura pode ser um fator estimulante da eclosão. O tempo médio de eclosão aumentou com a temperatura, variando de 2,8h (25ºC) a 5,2h (35ºC). A duração do período larval apresentou grande variabilidade dentro de cada grupo, embora não tenha diferido significativamente entre os mesmos (11,0 ± 4,19 dias), tendo sido mais longo para indivíduos mantidos na água a 35°C (12,0 ± 4,95 dias) e temperatura ambiente (13,6 ± 5,98 dias). Ao contrário, a sobrevivência das larvas foi fortemente afetada na temperatura mais elevada, onde apenas um indivíduo alcançou o estágio adulto. Esses resultados sugerem que a população de Ae. albopictus de Recife pode estar em processo de adaptação ao aumento de temperatura e que o limite para o desenvolvimento de estágios larvais se encontra próximo a 35°C.

Desenvolvimento de Aphidius colemani Viereck (Hymenoptera: Braconidae, Aphidiinae) e alterações causadas pelo parasitismo no hospedeiro Aphis gossypii Glover (Hemiptera: Aphididae) em diferentes temperaturas / Development of Aphidius colemani Viereck (Hym.: Braconidae, Aphidiinae) and alterations caused by the parasitism in the host Aphis gossypii Glover (Hem.: Aphididae) in different temperatures

Aphidius colemani Viereck está entre os principais inimigos naturais utilizados no controle biológico de Aphis gossypii Glover. Os objetivos deste trabalho foram avaliar o desenvolvimento de A. colemani e as alterações causadas pelo parasitismo no hospedeiro A. gossypii em diferentes temperaturas e estimar as exigências térmicas do parasitóide. O experimento foi conduzido em câmaras climatizadas a 16, 19, 22, 25, 28 e 31 ± 1°C, com 70 ± 10 por cento U.R. e fotofase de 12h. Ninfas de 2° instar de A. gossypii foram parasitadas uma vez e individualizadas em tubos de vidro (2,5 cm x 8,5 cm), contendo disco foliar de pepino (2 cm) e solução agar/água a 1 por cento. O período da oviposição à formação da múmia (11,9; 9,8; 7,7; 6,4 e 6,4 dias) e o da oviposição ao adulto de A. colemani (19,4; 16,2; 12,6; 10,5 e 10,7 dias) diminuíram com o aumento da temperatura no intervalo de 16°C e 25°C. A porcentagem de múmias formadas e a de emergência do parasitóide, assim como a longevidade diminuíram com o incremento da temperatura. Não houve formação de múmias a 31°C. O parasitóide A. colemani apresentou temperatura base inferior de desenvolvimento de 5,94°C e constante térmica de 200 GD. As alterações ocasionadas no hospedeiro A. gossypii pelo parasitismo foram minimizadas na temperatura de 31°C, sendo que 98 por cento dos hospedeiros não apresentaram sintomas de parasitismo e produziram ninfas. A temperatura de 22°C foi a mais adequada para o desenvolvimento de A. colemani.

Aphidius colemani Viereck is among the main natural enemies used for biological control of Aphis gossypii Glover. The objective of the present study was to evaluate the development of A. colemani and the alterations caused by the parasitism in the host A. gossypii in different temperatures and to estimate the thermal requirements of the parasitoid. The experiments were carried out in controlled environmental chambers at 16, 19, 22, 25, 28 and 31 ± 1°C, 70 ± 10 percent RH, and 12h photophase. Second-instar nymphs of A. gossypii were parasitized once and kept individually in glass tubes (2.5 cm x 8.5 cm), containing leaf disc of cucumber (2 cm) and 1 percent water/agar solution. The development time of A. colemani, from oviposition to mummies (11.9, 9.8, 7.7, 6.4 and 6.4 days) and from oviposition to adult (19.4, 16.2, 12.6, 10.5 and 10.7 days) decreased with the increase of the temperature from 16°C to 25°C. The rates of mummies and the emergence of the parasitoid, and its longevity also decreased with the increase of the temperature. Mummies were not produced at 31°C. The lower temperature threshold of A. colemani was 5.94°C and its thermal constant was 200 degrees-day. The alterations caused by the parasitoid in the A. gossypii host were minimized at 31°C, where 98 percent of the host did not show symptoms of parasitism and produced nymphs. The temperature of 22°C was optimal for the development time of A. colemani.

Exigências Térmicas, Período de Desenvolvimento e Sobrevivência de Imaturos de Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) / Thermal Requirements, Development and Survival of the Immature Stages of the Alphitobius diaperinus (Panz. ) (Coleoptera: Tenebrionidae)

The development and survival of the immature stages of the lesser mealworm Alphitobius diaperinus (Panzer) were studied at four constant temperatures (22°C, 25°C, 28°C, and 31°C). The development was completed at all temperatures. At 22°C, longer development period and lower survival were observed. The optimal temperature was 31°C which promoted shorter development and higher survival. The basal temperature and thermal constant for egg, larva and pupa development were: 17.8°C, 19.2°C, and 16.5°C and 40.09, 239.48 and 59.56 degree-days, respectively.

Estudou-se, em laboratório, o efeito de quatro temperaturas constantes (22°C, 25°C, 28°C e 31°C) sobre as fases imaturas de Alphitobius diaperinus (Panzer). Houve desenvolvimento de imaturos nas quatro temperaturas estudadas, sendo que a 22°C observou-se maior duração do desenvolvimento e menor sobrevivência. A temperatura de 31°C foi a mais favorável para o desenvolvimento dos imaturos, com alta sobrevivência. Os estágios de ovo, larva e pupa apresentaram temperatura base (Tb) de 17,8°C, 19,2°C e 16,5°C, respectivamente. As constantes térmicas (K) foram de 40,09 graus-dia (GD) para ovo, 239,48 GD para larva e 59,56 GD para pupa.