Formation and Development of Pseudothecia of Venturia nashicola

Conidia are believed to be the main source of primary inoculum for pear scab, caused by Venturia nashicola, in northern China. Experiments were conducted to investigate the development and potential role of V. nashicola ascospores in northern China. Leaves with pear scab lesions were collected from commercial orchards in November 2003 and 2004 to monitor pseudothecia formation under various environments. Pseudothecium production was shown to occur readily in northern China. The key requirement for pseudothecium production is the occurrence of rain during the winter and early spring, although the exact timing of these rain events appeared not to affect their development. Excess water may lead to the accelerated leaf decay and hence lead to production of fewer pseudothecia. More than 80% scabbed leaves, placed in a pear orchard, produced pseudothecia. Leaves with only non‐sporulating scab lesions in autumn were also able to produce a large number of pseudothecia. Both airborne ascospores and conidia of V. nashicola were caught in a pear orchard. Most ascospores were released by late‐May, a month after pear blossom. These results suggest that ascospores may play an important role in the early stage of pear scab epidemics in spring in northern China.     

Potential for redistribution of post-moult habitat for Eudyptes penguins in the Southern Ocean under future climate conditions

Anthropogenic climate change is resulting in spatial redistributions of many species. We assessed the potential effects of climate change on an abundant and widely distributed group of diving birds, Eudyptes penguins, which are the main avian consumers in the Southern Ocean in terms of biomass consumption. Despite their abundance, several of these species have undergone population declines over the past century, potentially due to changing oceanography and prey availability over the important winter months. We used light-based geolocation tracking data for 485 individuals deployed between 2006 and 2020 across 10 of the major breeding locations for five taxa of Eudyptes penguins. We used boosted regression tree modelling to quantify post-moult habitat preference for southern rockhopper (E. chrysocome), eastern rockhopper (E. filholi), northern rockhopper (E. moseleyi) and macaroni/royal (E. chrysolophus and E. schlegeli) penguins. We then modelled their redistribution under two climate change scenarios, representative concentration pathways RCP4.5 and RCP8.5 (for the end of the century, 2071–2100). As climate forcings differ regionally, we quantified redistribution in the Atlantic, Central Indian, East Indian, West Pacific and East Pacific regions. We found sea surface temperature and sea surface height to be the most important predictors of current habitat for these penguins; physical features that are changing rapidly in the Southern Ocean. Our results indicated that the less severe RCP4.5 would lead to less habitat loss than the more severe RCP8.5. The five taxa of penguin may experience a general poleward redistribution of their preferred habitat, but with contrasting effects in the (i) change in total area of preferred habitat under climate change (ii) according to geographic region and (iii) the species (macaroni/royal vs. rockhopper populations). Our results provide further understanding on the regional impacts and vulnerability of species to climate change.     

江苏地区烟粉虱的越冬研究

通过室内模拟寒潮、越冬大棚内虫量观察,以及冬后田间调查,研究江苏地区烟粉虱的越冬状况。结果表明,在0℃以上的环境温度下,72 h内各虫态烟粉虱均不会造成急性致死,在-2℃的环境温度下,1 h内低龄若虫开始死亡,24 h后高龄若虫开始死亡,6 h后卵全部死亡。在-4℃的环境温度下,6 h后烟粉虱所有虫态均全部死亡。在单膜覆盖的大棚内,烟粉虱成虫在-2.5℃的寒潮下全部死亡,在双膜覆盖的大棚内,烟粉虱可以安全越冬。研究认为,在江苏地区,烟粉虱可以在日光温室或双膜覆盖的大棚内越冬,苏南部分地区可以在单膜覆盖的大棚内越冬。     

Population limitation of the northern red-backed vole in the boreal forests of northern Canada

1. Across the vast boreal forests of North America, no population cycles in Clethrionomys species occur. In Eurasia, by contrast, some Clethrionomys populations of the same species undergo regular 3-5-year cycles. We examined the effects of nutrients, food, competitors, predators and climate on population limitation in the northern red-backed vole (Clethrionomys rutilus Pallas) in the south-western Yukon to determine why this difference occurs. 2. From 1986 to 1996 we added food, reduced large mammal predators and excluded snowshoe hares (Lepus americanus Erxleben) from large plots and found that none of these manipulations affected red-backed vole abundance. Adding nutrients as nitrogen, phosphorus and potassium (NPK) fertilizer had a slight negative effect, probably acting through a reduction in dwarf shrub productivity caused by competition from grasses. 3. We monitored weasel populations directly through trapping and indirectly through snow tracking. Predation by these vole specialists was irrelevant as a limiting factor most of the time because voles in this area do not reach the densities needed to sustain weasel populations. Other boreal forest mammal and bird predators did not focus on red-backed voles. However, when red-backed vole populations increased in the forest and Microtus voles also increased in the meadows, weasel populations increased and may have temporarily depressed red-backed voles in winter. 4. We monitored one major potential food, white spruce seeds, but seed fall was not related to population changes in red-backed voles, even after mast years. 5. We assessed the impact of weather variables, and the average depth of the snow pack during winter (October-March) was correlated directly with vole demography, having both direct effects in that year and delayed effects in the following year. 6. Our long-term trapping data (1973-96) indicate that Clethrionomys populations fluctuated, with peaks following hare peaks by 2-3 years. 7. We propose that the key variable limiting these vole populations is overwinter survival, and this is a function of overwinter food from berries produced during the previous summer by dwarf shrubs. These shrubs may be stimulated by abundant moisture from winter snows or by periodic fertilization from large quantities of pellets produced at snowshoe hare peaks.     

气候变暖对油松毛虫幼虫越冬及上下树发生期的影响

温度是影响害虫生长发育最重要的因素之一,为了解气温的变化趋势以及在此背景下油松毛虫Dendrolimus tabulaeformis Tsai et Liu幼虫越冬及上下树的动态变化,本文根据辽宁省建平县1988—2009年期间油松毛虫上下树发生期资料和气象资料,分析了建平县气温年变化趋势和油松毛虫上下树发生期年变化趋势,探讨了发生期与气温之间的相关性,结果表明:近22年(1988—2009)建平县气侯变暖的趋势显著,线性倾向估计分析发现年均气温、年均最低气温和年均最高气温均呈现出上升趋势,气候倾向率分别达0.50、0.59和0.36℃/10年,四季中春季气温的升幅最大,夏秋两季次之,冬季最低。在此气候变暖背景下油松毛虫幼虫上下树及越冬发生着一定的变化趋势,其中:下树总体呈现出提前发生、提前结束、下树历期缩短的变化趋势;翌年幼虫上树期则呈现出延迟发生、提前结束、上树历期缩短的变化趋势;整个越冬期长度则呈现出延长的变化趋势。相关性分析认为气候变暖对油松毛虫的下树活动具有直接影响,主要表现为下树结束期随气候变暖而显著提前,在不考虑其它因素的影响下,9—10月均气温上升1℃则下树结束期会提前约2 d,而幼虫越冬及上树发生期表现为并不受气候变暖的直接影响。研究结果为有效控制油松毛虫危害提供了理论依据。     

Density-Dependent Multiplication and Survival Rates in Heterodera glycines

Seasonal multiplication and overwinter survival are density-dependent in Heterodera glycines. At low to moderate population densities, the nematode is capable of large population increases on susceptible soybean cultivars and high rates of oversummer or overwinter survival in the absence of a host. To improve estimates of H. glycines multiplication and survival rates, egg densities were monitored for 12 cropping sequences across 10 years. Log-linear regression analysis was used to describe and compare density-dependent relationships. Growing-season change in H. glycines egg densities was density-dependent for all crops (susceptible soybean, resistant soybean, and nonhost), with slope estimates for the density-dependent relationship greater for susceptible soybean compared with a non-host crop. Overwinter population change also was density-dependent, with similar declines in survival rates observed for all crops as population densities increased. Survival was greater following susceptible soybean compared with resistant soybean, with an intermediate rate of survival associated with non-host crops. Survival estimates greater than 100% frequently were obtained at low population densities, despite attempts to account for sampling error. Rates of growing-season multiplication and survival, when standardized for population density, declined with year of the study. Standardized overwinter survival rates were inversely related to average daily minimum temperature and monthly snow cover.     

枸杞木虱成虫携带瘿螨越冬

多年来一直认为枸杞瘿螨Aceria pallida Kefer以成螨在树皮缝和芽缝内越冬,我们在宁夏中宁最新调查发现,大量瘿螨若螨潜伏于枸杞木虱越冬成虫体壁缝隙,尤其以后足基节与腹部缝隙最多。初步调查结果显示,越冬枸杞木虱Poratrioza sinica Yang et Li成虫雌性和雄性成虫均携带瘿螨成螨和若螨,平均2~3头,最多的可达30头。如果枸杞瘿螨随枸杞木虱越冬成虫越冬成为主要途径,那么对枸杞木虱越冬成虫的防治将成为控制枸杞瘿螨危害的重要防治策略和技术手段。     

High within‐winter and annual survival rates in a declining Afro‐Palaearctic migratory bird suggest that wintering conditions do not limit populations

For migratory birds, it is necessary to estimate annual and overwinter survival rates, identify factors that influence survival, and assess whether survival varies with age and sex if we are to understand population dynamics and thus inform conservation. This study is one of the first to document overwinter and annual survival from the wintering grounds of a declining Afro‐Palaearctic migrant bird, the Whinchat Saxicola rubetra. We monitored a population of marked individuals for which dispersal was low and detectability was high, allowing accurate estimates of survival. Annual survival was at least 52% and did not differ significantly across demographic groups or with habitat characteristics or residency time in the previous winter. Overwinter survival was very high and monthly survival at least 98% at some sites. Although winter residency varied spatially and with age, lower residency did not correlate with reduced annual survival, suggesting occupancy of multiple wintering sites rather than higher winter mortality of individuals with shorter residency. Our results suggest that mortality occurs primarily outside the wintering period, probably during migration, and that wintering conditions have minimal influence on survival. The similarity between survival rates for all age and sex classes when measured on the wintering grounds implies that any difference in survival with age or sex occurs only during the first migration or during the post‐fledging stage, and that selection of wintering habitat, or territory quality, makes little difference to survival in Whinchats. Our findings suggest that the wintering grounds do not limit populations as much as the migratory and breeding stages, with implications for the conservation of declining Afro‐Palaearctic migrants more widely.     

Influence of sex, body size, and reproduction on overwinter lipid depletion in brook trout

Expressed as percentages of total fresh body weight, lipids of brook trout Salvelinus fontinalis declined between October and April: reproductive males from 2·89 to 1·22%, reproductive females from 3·19 to 1·84%, and non-reproductive males and females from 2·75 to 2·08%. The absolute and proportional overwinter reduction in lipids among reproductive trout was more than twice that of non-reproductive trout, with reproductive males losing significantly more lipids than reproductive females. Larger reproductive individuals lost more lipids during winter, relative to body size, than smaller individuals, although such an effect was not evident among non-reproductive trout. The average overwinter reduction in lipids for reproductive males (58%), females (42%), and non-reproductive trout (24%) was negatively associated with mark-recapture estimates of overwinter survival probabilities of 0·27, 0·36, and 0·58, respectively, providing support for the hypothesis that energy is allocated to reproduction to the detriment of post-reproductive survival. Our emergent hypothesis that reproductive costs differ between sexes, and the life history consequences thereof, merit further study.