Leaf trait variation captures climate differences but differs with species irrespective of functional group

Aims To clarify whether variation in leaf traits with climate differs with scale, i.e. across species and within a species, and to detect whether plant functional group affects species-specific response.Methods Leaf dry matter content (LDMC), specific leaf area (SLA), mass- and area-based leaf N (N mass, N area) and leaf P concentrations (P mass, P area) and leaf chlorophyll concentration (SPAD) were measured for 92 woody plant species in two botanical gardens in China. The two gardens share plant species in common but differ in climate. Leaf trait variation between the two gardens was examined via mean comparison at three scales: all species together, species grouped into plant functional groups and within a species. A meta-analysis was performed to summarize the species-specific responses.Important findings At the scale of all species together, LDMC, SLA, P mass and N mass were significantly lower in the dry-cold habitat than in the wet-warm one, whereas N area and SPAD showed an inverse pattern, indicating a significant environmental effect. The meta-analysis showed that the above-mentioned patterns persisted for SLA, N area and SPAD but not for the other variables at the species-specific scale, indicating that intraspecific variation affects the overall pattern of LDMC, P mass and N mass and P area. In terms of species-specific response, positive, negative or nonsignificant patterns were observed among the 92 species. Contrary to our prediction, species-specific responses within a functional group were not statistically more similar than those among functional groups. Our results indicated that leaf trait variation captured climatic difference yet species-specific responses were quite diverse irrespective of plant functional group, providing new insights for interpreting trait variability with climate.     

Aegilops conservation and collection evaluation in the Czech Republic

Aegilops distribution was revised on localities in the territory of the Czech Republic and the former Czechoslovakia, based on herbarium data, literature and floristic databases. The only surviving species Ae. cylindrica forms the northern limit of distribution in the Danube basin, other sites are secondary. In situ conservation was proposed for two Czech sites where Aegilops have been naturalized. An ex situ gene bank collection has been maintained in the Gene Bank Prague since 1985. The collection includes 21 species and 1099 accessions. The whole collection was evaluated for breeding-valuable characters: resistance to leaf diseases, cereal aphids, viral diseases, and qualitative parameters. Recently, the collection was retested for the present races of leaf and stem rust including new introductions from Kazakhstan. Six different leaf rust races and five different stem rust races collected from the Czech Republic were applied in the older tests, and three races from each rust species in the recent tests. The highest number of accessions resistant both to wheat leaf rust and wheat stem rust and powdery mildew was found in Ae. speltoides (90%). Different reactions of individual accessions of the tested species to the three different pathotypes of each rust species indicates that several diverse genes for specific resistance are present in the accessions of the tested species.     

Multi-scale phylogenetic structure in coastal dune plant communities across the globe

Aims Studies integrating phylogenetic history and large-scale community assembly are few, and many questions remain unanswered. Here, we use a global coastal dune plant data set to uncover the important factors in community assembly across scales from the local filtering processes to the global long-term diversification and dispersal dynamics. Coastal dune plant communities occur worldwide under a wide range of climatic and geologic conditions as well as in all biogeographic regions. However, global patterns in the phylogenetic composition of coastal dune plant communities have not previously been studied.Methods The data set comprised vegetation data from 18463 plots in New Zealand, South Africa, South America, North America and Europe. The phylogenetic tree comprised 2241 plant species from 149 families. We calculated phylogenetic clustering (Net Relatedness Index, NRI, and Nearest Taxon Index, NTI) of regional dune floras to estimate the amount of in situ diversification relative to the global dune species pool and evaluated the relative importance of land and climate barriers for these diversification patterns by geographic analyses of phylogenetic similarity. We then tested whether dune plant communities exhibit similar patterns of phylogenetic structure within regions. Finally, we calculated NRI for local communities relative to the regional species pool and tested for an association with functional traits (plant height and seed mass) thought to vary along sea–inland gradients.Important findings Regional species pools were phylogenetically clustered relative to the global pool, indicating regional diversification. NTI showed stronger clustering than NRI pointing to the importance of especially recent diversifications within regions. The species pools grouped phylogenetically into two clusters on either side of the tropics suggesting greater dispersal rates within hemispheres than between hemispheres. Local NRI plot values confirmed that most communities were also phylogenetically clustered within regions. NRI values decreased with increasing plant height and seed mass, indicating greater phylogenetic clustering in communities with short maximum height and good dispersers prone to wind and tidal disturbance as well as salt spray, consistent with environmental filtering along sea–inland gradients. Height and seed mass both showed significant phylogenetic signal, and NRI tended to correlate negatively with both at the plot level. Low NRI plots tended to represent coastal scrub and forest, whereas high NRI plots tended to represent herb-dominated vegetation. We conclude that regional diversification processes play a role in dune plant community assembly, with convergence in local phylogenetic community structure and local variation in community structure probably reflecting consistent coastal-inland gradients. Our study contributes to a better understanding of the globally distributed dynamic coastal ecosystems and the structuring factors working on dune plant communities across spatial scales and regions.     

应用结构方程模型解析影响黄连木果实产量 和种子命运的因素

果实(种子)产量和质量是影响植物种群更新的重要因素。为了探明影响黄连木果实产量和种子命运的因素以及这些影响因素之间的相互作用, 作者于2009年对河南省济源市45株黄连木(Pistacia chinensis)结果样树的植株特征、果实特征、果实产量和种子命运等进行了测定, 并用结构方程模型进行综合分析。结果表明: (1)黄连木果实产量与树高、树冠面积和果序大小等特征成正相关, 但与胸径、果实大小相关性不显著; (2)与捕食者饱和假说的预测不一致, 单株果实产量对黄连木广肩小蜂(Eurytoma plotnikovi)的种子捕食率(即虫蛀率)无显著直接负向效应; (3)树高和果实大小对虫蛀率为显著直接正向效应, 胸径对虫蛀率为显著直接负向效应, 显示黄连木广肩小蜂对植株特征和果实特征有一定的选择能力; (4)空壳率与虫蛀率成显著负相关, 空壳果实越多, 越易逃避黄连木广肩小蜂的寄生, 空壳果实的存在对完好种子起到了一定保护作用, 可能是黄连木防御昆虫寄生的重要机制; (5)空壳率和虫蛀率对种子完好率有显著直接负向效应, 而胸径、果序大小和果实产量对完好率为间接正向效应, 树高和果实大小为间接负向效应。可见, 黄连木植株特征和果实特征均不同程度地影响其果实产量和昆虫寄生, 从而影响黄连木的种子质量和种群更新。     

内蒙古大针茅草原常见植物在不同土地利用方式下的固碳相关属性

为了探究植物与固碳相关属性在不同功能群、器官和物种间的差异, 以及这些属性对不同土地利用方式的响应, 2012年8月对内蒙古大针茅草原的4个样地(长期无干扰样地、长期自由放牧样地、4年围封样地和4年围封割草样地)进行了群落调查, 并采集样地中的常见植物, 测定了与植物固碳相关的属性, 包括全碳含量、全氮含量、碳氮比、纤维素含量、木质素含量和酸性洗涤纤维含量等。以常见植物为对象, 在功能群水平研究了各土地利用方式下全碳含量、全氮含量和碳氮比的差异; 针对各样地的共有种——糙隐子草(Cleistogenes squarrosa)、大针茅(Stipa grandis)、冷蒿(Artemisia frigida)、羊草(Leymus chinensis)和猪毛菜(Salsola collina), 从物种和器官水平分析了不同土地利用方式下植物的固碳相关属性。结果表明: 大针茅草原植物不同功能群、物种和器官间的固碳相关属性存在极显著差异, 不同土地利用方式下大针茅草原不同功能型、物种和器官的固碳相关属性有显著差异。与其他利用方式相比, 4年围封割草对植物与固碳相关属性的影响最为明显, 功能群、器官和物种水平的植物氮含量均有下降。糙隐子草和猪毛菜的这些属性对长期自由放牧的响应敏感, 且方向相反。     

The roles of geological history and colonization abilities in genetic differentiation between mammalian populations in the Philippine archipelago

Aim To test hypotheses that: (1) late Pleistocene low sea‐level shorelines (rather than current shorelines) define patterns of genetic variation among mammals on oceanic Philippine islands; (2) species‐specific ecological attributes, especially forest fidelity and vagility, determine the extent to which common genetic patterns are exhibited among a set of species; (3) populations show reduced within‐population variation on small, isolated oceanic islands; (4) populations tend to be most highly differentiated on small, isolated islands; and (5) to assess the extent to which patterns of genetic differentiation among multiple species are determined by interactions of ecological traits and geological/geographic conditions. Location The Philippine Islands, a large group of oceanic islands in Southeast (SE) Asia with unusually high levels of endemism among mammals. Methods Starch‐gel electrophoresis of protein allozymes of six species of small fruit bats (Chiroptera, Pteropodidae) and one rodent (Rodentia, Muridae). Results Genetic distances between populations within all species are not correlated with distances between present‐day shorelines, but are positively correlated with distances between shorelines during the last Pleistocene period of low sea level; relatively little intraspecific variation was found within these ‘Pleistocene islands’. Island area and isolation of oceanic populations have only slight effects on standing genetic variation within populations, but populations on some isolated islands have heightened levels of genetic differentiation, and reduced levels of gene flow, relative to other islands. Species associated with disturbed habitat (all of which fly readily across open habitats) show more genetic variation within populations than species associated with primary rain forest (all of which avoid flying out from beneath forest canopy). Species associated with disturbed habitats, which tend to be widely distributed in SE Asia, also show higher rates of gene flow and less differentiation between populations than species associated with rain forest, which tend to be Philippine endemic species. One rain forest bat has levels of gene flow and heterozygosity similar to the forest‐living rodent in our study. Main conclusions The maximum limits of Philippine islands that were reached during Pleistocene periods of low sea level define areas of relative genetic homogeneity, whereas even narrow sea channels between adjacent but permanently isolated oceanic islands are associated with most genetic variation within the species. Moreover, the distance between ‘Pleistocene islands’ is correlated with the extent of genetic distances within species. The structure of genetic variation is strongly influenced by the ecology of the species, predominantly as a result of their varying levels of vagility and ability to tolerate open (non‐forested) habitat. Readily available information on ecology (habitat association and vagility) and geological circumstances (presence or absence of Pleistocene land‐bridges between islands, and distance between oceanic islands during periods of low sea level) are combined to produce a simple predictive model of likely patterns of genetic differentiation (and hence speciation) among these mammals, and probably among other organisms, in oceanic archipelagos.     

Host age and fitness-related traits in a koinobiont aphid parasitoid

Abstract.  1. Trade-offs play a key role in species evolution and should be found in host–parasitoid interactions where the host quality may differ between host age categories.
2. The braconid wasp, Aphidius ervi , is a solitary endoparasitoid that allows its aphid hosts to continue to feed and grow after parasitisation. The hypotheses that host age influences their quality and that female parasitoids exploit their hosts based on that quality were tested under laboratory conditions using no-choice tests.
3.  Aphidius ervi females accepted the aphid Myzus persicae for oviposition and their progeny developed successfully in all host ages. The fitness-related traits of parasitoids did not increase linearly with the host age in which they developed. Host quality was found to be optimal at intermediate host ages and the females preferred to parasitise these hosts. The shortest progeny development time and a more female-biased sex ratio were observed in hosts of intermediate age.
4. This study suggests the existence of multiple interactive trade-offs occurring during host–parasitoid interactions according to host age related quality.     

Continuous monitoring of phytoplankton dynamics in Lake Balaton (Hungary) using on-line delayed fluorescence excitation spectroscopy

1. This study introduces delayed fluorescence (DF) excitation spectroscopy as an on‐line tool for in situ monitoring of the composition and biomass of various colour classes of phytoplankton when they are photosynthetically active (cyanobacteria, chlorophytes, chromophytes and cryptophytes). The DF data are validated by comparison with those from conventional methods (weekly microscopic counts and the measurement of chlorophyll concentration). 2. The composition of phytoplankton as assessed by DF agreed reasonably well with the results from microscopic counts, particularly when differences in chlorophyll‐specific DF integrals of the various colour classes were taken into account. 3. Integrals of DF spectra were converted into concentration of chlorophyll a using empirical factors derived from field data. The value of the conversion factor was nearly twice as high when the relative abundance of cyanobacteria was low (<15%) than when it was high. The converted DF‐chl time series agreed well with chlorophyll measurements particularly when blooms were developing. As the DF method is inherently free of the interference caused by pigment degradation products, the discrepancy between the two data sets increased during the collapse of blooms and when sediment resuspension was intense. 4. Fourier spectrum analysis of the time series of DF‐chl indicated that samples must be taken, at a minimum, every 2–3 days to capture the dynamics of phytoplankton. As a consequence, the dynamics of various algal blooms, including their timing, duration and net growth rate, could be estimated with greater confidence than by using conventional methods alone. 5. On‐line DF spectroscopy is an advanced technique for monitoring daily the biomass and composition of the photosynthetically active phytoplankton in aquatic environments, including turbid shallow lakes. At present, the detection limit is around 1 mg DF‐chl a m^?3 in terms of total biomass but confidence in estimates of phytoplankton composition declines sharply below about 5 mg chl a m^?3. 6. On‐line DF spectroscopy represents a promising approach for monitoring phytoplankton. It will be useful in water management where it can act as an early‐warning system of declines in water quality. In basic ecological research it can supplement manual methods. While default calibration spectra may be acceptable for routine monitoring, we suggest a careful individual calibration of the DF spectrometer for basic research. The statistical methods developed here help to assess the adequacy of various calibration sets.     

Leaf functional traits of Neotropical savanna trees in relation to seasonal water deficit

The seasonal savannas (cerrados) of Central Brazil are characterized by a large diversity of evergreen and deciduous trees, which do not show a clear differentiation in terms of active rooting depth. Irrespective of the depth of the root system, expansion of new foliage in deciduous species occurs at the end of the dry season. In this study, we examined a suite of leaf traits related to C assimilation, water and nutrients (N, P) in five deciduous and six evergreen trees that were among the dominant families of cerrado vegetation. Maximum CO₂ assimilation on a mass basis (A_mass) was significantly correlated with leaf N and P, and specific leaf area (SLA; leaf area per unit of leaf mass). The highest leaf concentrations of both nutrients were measured in the newly mature leaves of deciduous species at the end of the dry period. The differences in terms of leaf N and P between evergreen and deciduous species decreased during the wet season. Deciduous species also invested less in the production of non-photosynthetic leaf tissues and produced leaves with higher SLA and maintained higher water use efficiency. Thus, deciduous species compensated for their shorter leaf payback period by maintaining higher potential payback capacity (higher values of A_mass) and lower leaf construction costs (higher SLA). Their short leafless period and the capacity to flush by the end of the dry season may also contribute to offset the longer payback period of evergreen species, although it may involve the higher cost of maintaining a deep-root system or a tight control of plant water balance in the shallow-rooted ones.     

Generalized Linear Dynamics of a Plant-Parasitic Nematode Population and the Economic Evaluation of Crop Rotations

In 1-year experiments, the final population density of nematodes is usually modeled as a function of initial density. Often, estimation of the parameters is precarious because nematode measurements, although laborious and expensive, are imprecise and the range in initial densities may be small. The estimation procedure can be improved by using orthogonal regression with a parameter for initial density on each experimental unit. In multi-year experiments parameters of a dynamic model can be estimated with optimization techniques like simulated annealing or Bayesian methods such as Markov chain Monte Carlo (MCMC). With these algorithms information from different experiments can be combined. In multi-year dynamic models, the stability of the steady states is an important issue. With chaotic dynamics, prediction of densities and associated economic loss will be possible only on a short timescale. In this study, a generic model was developed that describes population dynamics in crop rotations. Mathematical analysis showed stable steady states do exist for this dynamic model. Using the Metropolis algorithm, the model was fitted to data from a multi-year experiment on Pratylenchus penetrans dynamics with treatments that varied between years. For three crops, parameters for a yield loss assessment model were available and gross margin of the six possible rotations comprising these three crops and a fallow year were compared at the steady state of nematode density. Sensitivity of mean gross margin to changes in the parameter estimates was investigated. We discuss the general applicability of the dynamic rotation model and the opportunities arising from combination of the model with Bayesian calibration techniques for more efficient utilization and collection of data relevant for economic evaluation of crop rotations.