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The influence of landscape and environmental factors on ranavirus epidemiology in a California amphibian assemblage 
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下载免费PDF全文 Brian J. Tornabene Andrew R. Blaustein Cheryl J. Briggs Dana M. Calhoun Pieter T. J. Johnson Travis McDevitt‐Galles Jason R. Rohr Jason T. Hoverman 《Freshwater Biology》2018,63(7):639-651
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ZHENKANG XU 《Freshwater Biology》1993,30(1):181-186
- 1 The effects of infection by Epistylis daphniae on its host, Moina macrocopa, were studied in the laboratory at 28°C by comparing the growth, reproduction and survival between infected and uninfected hosts.
- 2 Infestation by epizoites had little or no effect on the survival of the dadoceran hosts when adequate food was present.
- 3 The infected cladocerans had lower growth rates as juveniles, lower net reproduction rates as adults, and smaller body size at death than uninfected hosts.
- 4 The index of infection at different stages in the life cycle was related to the durations of intermoult period. Ranked in order of both index of infection and intermoult duration, the development stages were: old adult > young adult > juvenile.
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Markus Milchram Marcela Suarez‐Rubio Annika Schrder Alexander Bruckner 《Ecology and evolution》2020,10(3):1135-1144
- Automated recording units are commonly used by consultants to assess environmental impacts and to monitor animal populations. Although estimating population density of bats using stationary acoustic detectors is key for evaluating environmental impacts, estimating densities from call activity data is only possible through recently developed numerical methods, as the recognition of calling individuals is impossible.
- We tested the applicability of generalized random encounter models (gREMs) for determining population densities of three bat species (Common pipistrelle Pipistrellus pipistrellus, Northern bat Eptesicus nilssonii, and Natterer's bat Myotis nattereri) based on passively collected acoustical data. To validate the results, we compared them to (a) density estimates from the literature and to (b) Royle–Nichols (RN) models of detection/nondetection data.
- Our estimates for M. nattereri matched both the published data and RN‐model results. For E. nilssonii, the gREM yielded similar estimates to the RN‐models, but the published estimates were more than twice as high. This discrepancy might be because the high‐altitude flight of E. nilssonii is not accounted for in gREMs. Results of gREMs for P. pipistrellus were supported by published data but were ~10 times higher than those of RN‐models. RN‐models use detection/nondetection data, and this loss of information probably affected population estimates of very active species like P. pipistrellus.
- gREM models provided realistic estimates of bat population densities based on automatically recorded call activity data. However, the average flight altitude of species should be accounted for in future analyses. We suggest including flight altitude in the calculation of the detection range to assess the detection sphere more accurately and to obtain more precise density estimates.
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- 1 Abundance of leaf-mining larvae of the outbreak species Eriocrania spp. was monitored in northern Sweden in 1955–67 and 1984–92 in a mountain birch forest rejuvenated by an Epirrita autumnata outbreak in 1954–55.
- 2 Eriocrania mine density fluctuated in a regular biennial pattern, probably due to a semivoltine life cycle. The alternate year fluctuations had shifted phase between the two study periods.
- 3 The density fluctuated at a significantly higher mean level and with a lower amplitude in the c. 10-year-old forest in the 1960s than in the 30-year-old forest in the 1980s. However, no difference was found in mine density between c. 30- and >60-year-old stands in the 1980s.
- 4 Significant correlations between the density of mines in high-density years and date of budburst, and between rate of change between high-density years and the time between snow-melt and budburst indicate effects of weather. No correlation was found between yearly average mine density and date of budburst, precipitation or temperatures in May or June.
- 5 No correlation was found between the mean densities of Eriocrania mines and E.autumnata caterpillars in the same and the two preceding years. However, in the first (1955) and highest of three studied E.autumnata peaks a negative effect on population density of Eriocrania was indicated.
- 6 A significant, negative correlation between the number of Eriocrania mines and E.autumnata caterpillars on single branches was found in three out of eighteen years. The separation of caterpillars and mines at branch level indicates an effect of avoidance at intermediate population densities.
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Plagues caused by locusts and grasshoppers have led to severe crop damage and great economic loss in many countries. Nevertheless, populations of these pests are often suppressed by naturally occurring predators and disease. Among such natural control factors, the entomopathogenic fungus, Entomophaga grylli, can markedly disrupt the dynamics of grasshopper populations. However, there are few reports of epizootics of this entomopathogenic fungus occurring in consecutive years. Here we report on a consecutive 2-year field survey of E. grylli epizootics in Xinjiang, Northwest China. E. grylli were observed to infect at least four species of grasshopper, Calliptamus italicus, Gomphocerus sibiricus, Chorthippus sp., and Stauroderus scalaris. This is the first record of infection of the last two species by this pathogen. The highest infection rates at the two study sites (Chonghuer and Jiadengyu, Altay Prefecture) were ≥50%, observed in mid-July 2011, and the lowest rate was >16% in early summer. The density of infected grasshoppers was positively correlated with the density of total grasshoppers collected (r?=?0.981). Therefore, E. grylli is an important natural factor regulating the dynamics of grasshopper populations in regions that are not subjected to artificial treatments. 相似文献
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Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae) 总被引：3，自引：0，他引：3
GRAHAM J. HOLLOWAY 《Ecological Entomology》1993,18(3):209-217
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- 1 An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
- 2 The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
- 3 Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
- 4 There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
- 5 Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
- 6 The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.
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Insights into intraspecific wood density variation and its relationship to growth,height and elevation in a treeline species 下载免费PDF全文
下载免费PDF全文 A. Fajardo 《Plant biology (Stuttgart, Germany)》2018,20(3):456-464
- The wood economics spectrum provides a general framework for interspecific trait–trait coordination across wide environmental gradients. Whether global patterns are mirrored within species constitutes a poorly explored subject. In this study, I first determined whether wood density co‐varies together with elevation, tree growth and height at the within‐species level. Second, I determined the variation of wood density in different stem parts (trunk, branch and twigs).
- In situ trunk sapwood, trunk heartwood, branch and twig densities, in addition to stem growth rates and tree height were determined in adult trees of Nothofagus pumilio at four elevations in five locations spanning 18° of latitude. Mixed effects models were fitted to test relationships among variables.
- The variation in wood density reported in this study was narrow (ca. 0.4–0.6 g cm?3) relative to global density variation (ca. 0.3–1.0 g cm?3). There was no significant relationship between stem growth rates and wood density. Furthermore, the elevation gradient did not alter the wood density of any stem part. Trunk sapwood density was negatively related to tree height. Twig density was higher than branch and trunk densities. Trunk heartwood density was always significantly higher than sapwood density.
- Negative across‐species trends found in the growth–wood density relationship may not emerge as the aggregate of parallel intraspecific patterns. Actually, trees with contrasting growth rates show similar wood density values. Tree height, which is tightly related to elevation, showed a negative relationship with sapwood density.
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Sarah E. Lower Owais Gilani Madden J. Tuffy Deeshani N. Patel Zhengkai Zhu Moria C. Chambers 《Ecological Entomology》2023,48(1):90-101
- The degree to which host, pathogen, and environmental characteristics determine fitness outcomes in response to infection across the tree of life is a key question in ecoimmunology. Because infection experiments require large sample sizes and careful controls, studies have generally been limited to lab-adapted organisms.
- Photinus pyralis is a charismatic firefly that is abundant during its annual summer emergence in the Eastern United States. Here, we assess the importance of host condition, pathogen identity and dose, and pre-infection environment on survival outcomes in response to bacterial infection in wild-caught adult male P. pyralis.
- Although survival after sterile saline injection was not statistically different from survival of uninjected controls, survival kinetics support sterile saline injection as the most appropriate control.
- Serratia marcescens and Providencia rettgeri infections increased mortality, especially at high doses. In contrast to fruit fly studies, Providencia sneebia, Pseudomonas aeruginosa, and Enterococcus faecalis infections did not. Infection with higher doses of P. rettgeri had an increased risk of death for fireflies caught later in the season than those captured earlier, but seasonality did not significantly interact with dose to impact mortality with any of the other bacterial species.
- These results highlight the importance of considering host, pathogen, and environmental factors when investigating infection outcomes in wild-caught, non-model systems. The differences in survival between fireflies and fruit flies emphasise that further studies in a broad array of organisms are needed to explore the diversity of infection responses across the tree of life.
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