Insect seasonality: circle map analysis of temperature-driven life cycles

Maintaining an adaptive seasonality, with life cycle events occurring at appropriate times of year and in synchrony with cohorts and ephemeral resources, is a basic ecological requisite for many cold-blooded organisms. There are many mechanisms for synchronizing developmental milestones, such as egg laying (oviposition), egg hatching, cocoon opening, and the emergence of adults. These are often irreversible, specific to particular life stages, and include diapause, an altered physiological state which can be reversed by some synchronizing environmental cue (e.g. photoperiod). However, many successful organisms display none of these mechanisms for maintaining adaptive seasonality. In this paper, we briefly review the mathematical relationship between environmental temperatures and developmental timing and discuss the consequences of viewing these models as circle maps from the cycle of yearly oviposition dates and temperatures to oviposition dates for subsequent generations. Of particular interest biologically are life cycles which are timed to complete in exactly 1 year, or univoltine cycles. Univoltinism, associated with reproductive success for many temperate species, is related to stable fixed points of the developmental circle map. Univoltine fixed points are stable and robust in broad temperature bands, but lose stability suddenly to maladaptive cycles at the edges of these bands. Adaptive seasonality may therefore break down with little warning with constantly increasing or decreasing temperature change, as in scenarios for global warming. These ideas are illustrated and explored in the context of Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) occurring in the marginal thermal habitat of central Idaho's Rocky Mountains. Applications of these techniques have not been widely explored by the applied math community, but are likely to provide great insight into the response of biological systems to climate change.     

Target-specific PCR primers can detect and differentiate ophiostomatoid fungi from microbial communities associated with the mountain pine beetle Dendroctonus ponderosae

The aim of this study was to develop DNA probes that could identify the major fungal species associated with mountain pine beetles (MPB). The beetles are closely associated with fungal species that include ophiostomatoid fungi that can be difficult to differentiate morphologically. The most frequently isolated associates are the pine pathogens Grosmannia clavigera and Leptographium longiclavatum, the less pathogenic Ophiostoma montium, and an undescribed Ceratocystiopsis species (Cop. sp.). Because growing, isolating and extracting DNA from fungi vectored by MPB can be time and labour intensive, we designed three rDNA primer sets that specifically amplify short rDNA amplicons from O. montium, Cop. sp. and the pine Leptographium clade. We also designed two primer sets on a gene of unknown function that can differentiate G. clavigera and L. longiclavatum. We tested the primers on 76 fungal isolates that included MPB associates. The primers reliably identified their targets from DNA obtained from pure fungal cultures, pulverized beetles, beetle galleries, and tree phloem inoculated with G. clavigera. The primers will facilitate large-scale work on the ecology of the MPB-fungal-lodgepole pine ecosystem, as well as phytosanitary/quarantine sample screening.     

长白山北坡落叶松年轮年表及其与气候变化的关系

运用相关函数及单年分析等树木年轮气候学方法,研究了长白山北坡落叶松径向生长与气候变化的关系.结果表明,落叶松的生长对环境变化相当敏感,温度是影响其生长的主要因子.但不同海拔的落叶松对温度的响应明显不同.高海拔分布的落叶松只与当年6月的温度指标显著相关,而低海拔的落叶松与环境的关系相对复杂,除当年的4、5月外,上一年的6、9月温度以及上年9月的湿润指数都显著影响其生长.这说明不同环境梯度上的同一树种对气候变化的响应不尽相同.     

Ultrastructure of the mycangium of the southern pine beetle,Dendroctonus frontalis (Coleoptera: Curculionidae,Scolytinae): complex morphology for complex interactions

Yuceer, C, Hsu, C.‐Y., Erbilgin, N and Klepzig, K.D. 2011. Ultrastructure of the mycangium of the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae, Scolytinae): complex morphology for complex interactions. —Acta Zoologica (Stockholm) 92 : 216–224. The southern pine beetle (SPB) (Dendroctonus frontalis Zimmermann) is the most economically important pest of southern pine forests. Beetles carry fungal cells within specialised cuticular structures, called mycangia. Little is known about the mycangia ultrastructure or function. We used cryo‐fracturing and scanning electron microscopy to examine the ultrastructural features of SPB mycangia and surrounding tissues. Mycangia, one on each side of anterior portion of the prothorax, are terminated on the dorsal side at a ‘mycangial bridge’. This sclerotised mycangial bridge does not appear to provide a passage between the two mycangia, suggesting that each mycangium functions independently. Mycangia are surrounded by abundant tracheoles connecting the structures to the outside via openings within the prothorax. Previously unknown pits overlying the mycangial gland cells were also observed in both the inner wall and anterior fold of prothorax. We hypothesise that these openings and pits may play roles in determining which fungi enter, and grow within, the mycangium.     

长白山北坡落叶松年轮年表及其与气候变化的关系

运用相关函数及单年分析等树木年轮气候学方法,研究了长白山北坡落叶松径向生长与气候变化的关系.结果表明,落叶松的生长对环境变化相当敏感,温度是影响其生长的主要因子.但不同海拔的落叶松对温度的响应明显不同.高海拔分布的落叶松只与当年6月的温度指标显著相关,而低海拔的落叶松与环境的关系相对复杂,除当年的4、5月外,上一年的6、9月温度以及上年9月的湿润指数都显著影响其生长.这说明不同环境梯度上的同一树种对气候变化的响应不尽相同.     

紫茉莉的花部综合特征与繁育系统

采用定株观察,运用花粉-胚珠比、联苯胺-过氧化氢法、杂交指数和套袋实验等方法,对紫茉莉(Mirabilis jalapa L.)的开花状态及繁育系统进行了研究.结果表明:种群花期一般为6-10月,单花花期一般为2～3 d;单花花期依其形态和散粉时间可分为散粉前期、散粉初期、散粉盛期、花闭合期、凋谢期5个时期;在花闭合时期,晴天有66.80%的花的柱头在闭合花冠内,阴天时有81.65%的花的柱头在闭合花冠内,雨天柱头在闭合花冠内的花可达99.22%;按照杂交指数,其繁育系统属于自交亲和,有时需要传粉者;P/O值约为269,判断繁育系统类型属于兼性自交;开花6 h左右,柱头的可授性最强,此时花粉活力、置落在柱头上的花粉数及其在柱头上的萌发率都达到最高.套袋实验显示,紫茉莉自然条件下没有无融合现象,繁育系统为自交、异交亲和,以自交为主,但有时也需要传粉者;在长期的环境选择压力下,紫茉莉选择将更多的柱头留在闭合花冠内,是其对不利环境条件的一种适应进化策略.     

Dynamics of daily height growth in Scots pine trees at elevated temperature and CO2

The aim of this study was to analyse and model the effects of elevated temperature and carbon dioxide concentration on daily height growth of 20-year-old Scots pines (Pinus sylvestris L.). The trees were grown with a low nitrogen supply in closed chambers with a factorial combination of two temperature regimes (ambient and elevated) and two carbon dioxide concentrations (ambient and twice ambient). The temperature elevation corresponded to the predicted increase at the site after a doubling in atmospheric CO₂. The height growth of Scots pines was first empirically studied in terms of its onset, cessation and duration, and the allocation of daily height growth within the growing period in 2000 and 2001, and then a model predicting daily height growth as a function of daily temperature and temperature sum was developed. The empirical results showed elevated temperature to be the dominant variable explaining variation in daily height growth. Elevated temperature also hastened both the onset and cessation of height growth, and the temperature sums for both of them were higher in the elevated than in the ambient temperature treatments. The daily variation in height growth could also be explained by the daily mean temperature in the model. Elevated CO₂ concentration had no effect on the onset, cessation or duration of height growth. The amount of height growth was not affected by any of the treatments.     

东北阔叶红松林分布区生态气候适宜性及全球气候变化影响评价

以在植被分布中起重要作用的温度指标(生长度·日,GDD)和水分指标(可能蒸散率,PER)为基础提出温度·水分影响函数f(GDD,PER),评价丁东北阔叶红松林分布区生态气候环境质量即生态气候适宜性．将f(PER,GDD)≥0．70划为阔叶红松林核心分布区;0．35≤f(PER,GDD)＜0．70划为适宜分布区;f(PER,GDD)<0．35划为边缘分布区．东北阔叶红松林分布区面积为39．99km^2,其中核心分布区面积7．13×10^4kg^2,适宜分布区12．27km^2,边缘分布区20．59km^2。同时结合大气环流模式(GISS、OSU)的气候变化情景评价了全球气候变化对东北阔叶红松林分布区生态气候适宜性的影响．结果表明,于暖化气候条件下东北地区阔叶红松林分布区明显减小,生态适应性显著下降。     

Modeling the Evolution of Insect Phenology

Climate change is likely to disrupt the timing of developmental events (phenology) in insect populations in which development time is largely determined by temperature. Shifting phenology puts insects at risk of being exposed to seasonal weather extremes during sensitive life stages and losing synchrony with biotic resources. Additionally, warming may result in loss of developmental synchronization within a population making it difficult to find mates or mount mass attacks against well-defended resources at low population densities. It is unknown whether genetic evolution of development time can occur rapidly enough to moderate these effects. We present a novel approach to modeling the evolution of phenology by allowing the parameters of a phenology model to evolve in response to selection on emergence time and density. We use the Laplace method to find asymptotic approximations for the temporal variation in mean phenotype and phenotypic variance arising in the evolution model that are used to characterize invariant distributions of the model under periodic temperatures at leading order. At these steady distributions the mean phenotype allows for parents and offspring to be oviposited at the same time of year in consecutive years. Numerical simulations show that populations evolve to these steady distributions under periodic temperatures. We consider an example of how the evolution model predicts populations will evolve in response to warming temperatures and shifting resource phenology.