Mating system and pollen gene flow in Mediterranean maritime pine

Mating systems define the mode of gene transmission across generations, helping to determine the amount and distribution of genetic variation within and among populations of plant species. A hierarchical analysis of Mediterranean maritime pine mating system (61 mother trees from 24 plots, clustered in three populations) was used to identify factors affecting mating patterns and to fit pollen dispersal kernels. Levels of ovule and seed abortion, multi- and single-locus outcrossing rates and correlated paternity were estimated from progeny arrays and correlated with ecological stand variables and biometric tree measures. Pollen dispersal kernels were fitted using TwoGener and KinDist indirect methods and simulations were carried out to identify relevant factors affecting correlated paternity. Maritime pine showed high outcrossing rates (t(m) and t(s) approximately 0.96) and relatively low levels of correlated paternity [an r(p) of 0.018 (Ritland's estimate) or 0.048 (Hardy's estimate)], although higher than in other anemophilous tree species. Mating system parameters had high variation at the single-tree level (99-100%) but no stand or population effect was detected. At the single-tree level, outcrossing rates were correlated with tree (diameter and height) and crown size. In addition, correlated paternity showed a significant negative correlation with tree height, height to crown base and height to the largest crown width, probably reflecting the importance of the trees' 'ecological neighborhoods'. Indirectly estimated pollen dispersal kernels were very leptokurtic (exponential-power distributions with beta<0.5), with mean dispersal distances from 78.4 to 174.4 m. Fitted dispersal kernels will be useful in building explicit simulation models that include dispersal functions, and which will contribute to current conservation and management programs for maritime pine. Nevertheless, the numerical simulations showed that restricted dispersal, male fertility and phenological overlap could only partially explain the observed levels of correlated paternity; so other factors may also be relevant for the management of this valuable forest tree species.     

An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

Long-term trends in airborne fungal-spore concentrations: a comparison with pollen

We examined the long-term trends in airborne fungal-spore concentrations in Thessaloniki, Greece, over the period 1987–2005. We estimated trends in the spore levels for the 14 taxa that contribute at least 0.1 % to the total airborne spore concentration. We also tested for trends towards earlier, longer or more highly peaked spore seasons. There was decreasing concentration of spores for 11 of the 14 taxa, especially for Agrocybe, Botrytis, Cladosporium, and Nigrospora, where this trend was significant. Using ANCOVA, there was a highly significant negative trend overall (p < 0.001). Regarding the spore-season related attributes, there were very few significant trends. However, the main spore season tended to start later (for 12 of the 14 taxa) and become shorter (for 10 of the 14 taxa); later onset was more pronounced during the most recent part of the study period. Fungi seem to display a delayed and slower response to climate change than plants and in a direction opposite to that of pollen.     

Correlations between weather conditions and airborne pollen concentration and diversity in a Mediterranean high-altitude site disclose unexpected temporal patterns

Relationships between meteorological factors and airborne pollen concentrations at high altitudes are virtually unknown. We used cross-correlation analyses to test the relationships between daily variation in meteorological factors (i.e. temperature, humidity and wind speed) and airborne pollen concentration, diversity (number of families and Shannon and Simpson diversity indices) and evenness (Pielou index) in an Apennine high-altitude site (Gran Sasso Massif, 2117 m elevation). In contrast to patterns observed at low altitudes, the temperature had a negative correlation with pollen abundance and diversity, whereas humidity had a positive correlation. The unexpected negative correlations with temperature can be explained with the particular position of our sampling site. Wind speed was positively correlated with pollen diversity and abundance in the short term, which can be explained by the fact that higher wind speed promotes both primary emission of pollen from the anthers and subsequent re-suspension. Evenness and wind speed were negatively correlated in the short term because of the different response of different species to meteorological conditions. In the longer term, the average concentrations of the various taxa tend to reach similar values, leading to increased values of diversity. Our finding of a decrease in pollen emission with increasing temperature has important implications for the study of the impacts of global change on high-altitude plant communities. We also detected a high abundance of Cupressaceae/Taxaceae pollen, a reflection of the expansion of thermophilic species, such as Juniperus, due to climate change.     

Changes in airborne pollen concentrations in Delhi,India

In order to find the qualitative and quantitative changes in airborne pollen concentrations in Delhi metropolis area an aerobiological survey was undertaken from September 1990 to August 1997. Air samples were collected daily using a Rotorod Aeroallergen Sampler at 10?m above the ground level. Ninety-four pollen types were recorded and the major contributors include Morus, Cannabis, Chenopod/Amaranth, Prosopis, Artemisia, and Eucalyptus. Ten pollen types contributed 90% of the total pollen load. Two major pollen seasons were recorded each year (February–April and September–November), although pollen grains in low frequency were recorded throughout the whole year. A significant reduction in pollen concentration was observed in subsequent years. The number of Morus, Cannabis, Prosopis, and Artemisia pollen decreased considerably while the number of Ricinus communis pollen did not show any considerable change during the study period. It is suggested that the reduction in pollen numbers from 1990 to 1997 in Delhi is due to massive clearing of vegetation for developmental activities of the city.     

Theoretical daily variation patterns of airborne pollen in the southwest of spain

In this work we establish theoretical daily pollen variation grains for the 24 taxa most frequently occurring in the atmosphere of Córdoba (Spain) during three consecutive years, namely Alnus glutinosa, Broussonetia papyrifera, Casuarina equisetifolia, Chenopodiaceae, Amaranthaceae, Cupressaceae, Cyperaceae, Ericaceae, Fraxinus, Gramineae, Mercurialis, Morus, Myrtaceae, Olea europaea, Palmae, Pinaceae, Pistacia, Plantago, Platanus hybrida, Populus, Quercus, Rumex, Typha domingensis, Ulmus minor and Urticaceae. Sampling was carried out using a Burkard spore-trap and the data collected were used to establish theoretical patterns of daily variation represented by an ideal day with accounts for the daily behaviour of each taxon.

The application of centred-data analysis (CDA) allowed two groups of taxa to be established, namely (a) those with a homogeneous variation pattern and small differences between the times of maximum and minimum occurrence, and (b) those with a heterogeneous variation pattern arising from large differences between maxima and minima or from a rather erratic variation.

As a rule, maximum pollen concentrations were found to coincide with the times of maximum sunlight and temperature.     

Seed colour and post-fire bird predation in a Mediterranean pine forest

In a Pinus halepensis Mill. forest, a field experiment was designed to evaluate post-fire seed predation as affected by combinations of seed colour and soil substrates: light grey and black seeds combined with light grey ash, dark grey ash and pale brown sand. A survey of bird species inhabiting the area was also carried out and polyphenolic content of seed coat was assessed in seed lots of different colour. Light grey seeds were observed to be less predated on light grey ash, suggesting eucrypsis as a protective strategy against bird predation. On the contrary, no clear pattern was observed for the predation of black seeds on different substrates. In the study area both bird species breaking the seed coat and eating the endosperm and bird species swallowing the whole seed were monitored. We have estimated that more seeds were swallowed than broken, in all colour categories. Light grey seeds, which were found to have a higher content of polyphenols, were predated more than black seeds when exposed on the same substrate. Thus, no evidence was produced that the amount of polyphenols in seed coat could protect seeds from predation.     

Differences in pollen viability in relation to different deceptive pollination strategies in Mediterranean orchids

Background and Aims

To date, current research involving pollen viability has been evaluated in a relatively low number of orchid species. In the present study, we focused on five related Mediterranean orchid genera (Anacamptis, Orchis, Dactylorhiza, Ophrys and Serapias) that are characterized by different types of deceptive pollination.

Methods

The in vitro germination ability of increasingly aged pollinaria of eight food-, seven sexually and two shelter-deceptive species was evaluated. Pollination experiments on two food-, one sexually and one shelter-deceptive species were also performed and the percentage of embryonate seeds derived from the increasingly aged pollinaria was checked.

Key Results

All of the examined species showed long-term viabilities (=50 % pollen tube growth) that ranged from 8 to 35 d. Species with the same deceptive pollination strategies exhibited the same pollen viability trends. Interestingly, pollen viabilities of species groups with different deception types have shown significant differences, with sexually and shelter- deceptive species exhibiting a shorter life span than food-deceptive species.

Conclusions

This study confirms the prolonged germination and fertilization capacities of orchid pollinaria, and to our knowledge is the first report demonstrating a clear relationship between pollen viability and pollination system. It is proposed that this relationship is attributed to the different types of reproductive barriers, pre- or post-zygotic, that characterixe Ophrys and Serapias and the food-deceptive species, respectively.     

北京主要气传致敏花粉年浓度峰值日期预测

花粉是我国北方引发过敏性鼻炎最主要过敏原,花粉症发病期与花粉浓度高峰期吻合。基于北京地区2012至2020年花粉季多站、逐日分类花粉浓度观测数据分析,得出北京地区花粉浓度在3月上旬至5月中旬(可进一步划分为3月中旬至4月上旬和4月下旬至5月上旬两个高峰期)和8月中旬至9月中旬分别存在两个高峰期,第一个高峰期内优势致敏花粉种类为柏科、杨柳科和松科,第二个高峰期内优势致敏花粉种类为桑科、菊科蒿属和藜科。根据优势致敏花粉年浓度峰值日期观测数据,使用与花粉采样站点位置相匹配的逐日气象观测数据累积值,基于作物模型概念和模糊逻辑原理建立了北京地区主要气传致敏花粉年浓度峰值日期预测模型。经检验,柏科、杨柳科、松科、桑科、菊科蒿属和藜科花粉模型预测准确率分别为87.8%、80.0%、64.4%、86.7%、78.8%和81.8%。基于北京地区主要气传致敏花粉年浓度峰值日期预测模型可为本地花粉症防治提供理论参考。     

野慈姑(Sagittaria trifolia)人工授粉的有效性:授粉工具与花粉保存

人工授粉作为一项关键性技术在生态研究与农业生产领域广泛应用,但是授粉过程中的工具有效性以及花粉保存尚未受到研究者的关注。以植物野慈姑为试验材料,研究了人工授粉方式和花粉保存条件对繁殖的影响。两年的结果表明,相较于直接接触式授粉,借助毛刷工具授粉显著降低了野慈姑的座果概率和种子数。花粉经过半小时野外高温保存后,其授粉的座果概率显著高于对照组,但单果种子数和种子大小保持稳定。综上,在野慈姑的人工授粉中应避免使用毛刷等工具,离体花粉可置于野外环境适当保存。在相关应用中,研究人员应当警惕工具授粉造成的负面影响,注意比较工具与其他授粉方式的等效性,保证实验的科学性。     

湖北宜昌松林景观格局对松材线虫流行及扩散的影响

景观格局对能量流、物质流和物种流等生态学过程影响显著。为了探究区域生境差异对病虫害发生及扩散的影响,以湖北省宜昌市夷陵区松材线虫病为对象,结合区域森林资源二类清查矢量数据和松材线虫病普查资料,运用景观生态学的原理和方法,探究景观格局对松材线虫病发生的影响。研究结果表明:1)松林景观类型百分比、平均斑块面积、自然连接度和聚合度与松材线虫病的发病率成正相关;2)松林斑块的粒级结构分析表明,中、小斑块能抑制松材线虫病的发生,巨斑块、超大斑块对松材线虫的发生有利;3)从景观干扰上分析显示人类活动强度与松材线虫病发病率成正相关;4)在景观尺度水平上,景观的破碎度大、多样性指数高、蔓延度指数小、斑块形状简单、受人类活动影响大的乡镇松材线虫病发病率高。通过斑块类型尺度和景观尺度两个水平上的分析可知,在夷陵区乡镇尺度上,由小斑块松林组成且斑块聚集度低、景观破碎化程度低的景观格局对松材线虫病有一定的抑制作用。研究结论对当地松材线虫病的防治就有较好的参考价值。     

Spatial pattern of seedlings 1 year after fire in a Mediterranean pine forest

Summary The spatial distribution of seedlings of the dominant perennial plant species (Pinus halepensis, Cistus salviifolius, Rhus coriaria) and may annual species was studied after a wild fire in an eastern Mediterranean pine forest. The spatial distribution of all seedlings is affected by the location of the old burned pine trees. Seedling density of Pinus and Cistus is higher at a distance from the burned pine canopy and lower near the burned pine trunk. It is also higher beneath small burned pine trees than under big ones. Rhus seedling density is higher under big burned pine trees and also near the burned trunks. Seedlings of Pinus, Cistus and Rhus growing under the burned canopy of big pine trees tend to be taller than seedlings under small ones or outside the burned canopy. Most annual species germinate and establish themselves outside the burned canopies, and only a few annual species are found beneath them. It is suggested that variation in the heat of the fire, in the amount of ash between burned pine trees of different sizes, and in the distance from the burned canopy are responsible for the observed pattern of seedling distribution. The possible ecological significance of the spatial pattern of seedlings distribution and their differential growth rate are discussed.     

Seasonal distribution of pollen in the atmosphere of melbourne: an airborne pollen calendar

Environmental monitoring of pollen grains in the atmosphere of Melbourne has been achieved using Burkard volumetric traps. Twenty-two families of flowering plants and confiers were identified in the pollen counts. About 62% of these pollen grains belonged to trees, 20% to grasses and 9% to herbs and weedy plants. During spring and summer, the atmosphere contained about 70% of the total annual pollen count. Tree pollen, predominantly elm and cypress, occurred abundantly in late winter and spring, with grass pollen predominantly in spring and early summer. These three types of pollen grains occurred in significant amounts, together accounting for more than 60% of the total annual catch. A seasonal incidence chart (pollen calendar) for Melbourne based on 2 years observation has been constructed. This pollen calendar is useful in identifying sources of allergies against particular seasonal airborne pollen types. Comparison of the time of occurrence of a particular pollen type using the pollen calendar and the time of allergic symptoms, can lead to accurate diagnosis and preventive measures being taken. This study has confirmed that grass pollen is the major source of allergenic pollen in the external environment triggering hay fever and allergic asthma in spring and early summer in Melbourne, Australia.     

Aerial seed bank dynamics and seedling emergence patterns in two annual Mediterranean Asteraceae

Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non‐dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within‐season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph‐specific patterns of between‐year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between‐year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within‐year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within‐season, risk‐reducing traits in ruderal Mediterranean habitats characteristic of the study species.     

Seasonal and annual variation of carbon exchange in an evergreen Mediterranean forest in southern France

We present 9 years of eddy covariance measurements made over an evergreen Mediterranean forest in southern France. The goal of this study was to quantify the different components of the carbon (C) cycle, gross primary production (GPP) and ecosystem respiration (R_eco), and to assess the effects of climatic variables on these fluxes and on the net ecosystem exchange of carbon dioxide. The Puéchabon forest acted as a net C sink of ?254 g C m^?2 yr^?1, with a GPP of 1275 g C m^?2 yr^?1 and a R_eco of 1021 g C m^?2 yr^?1. On average, 83% of the net annual C sink occurred between March and June. The effects of exceptional events such the insect‐induced partial canopy defoliation that occurred in spring 2005, and the spring droughts of 2005 and 2006 are discussed. A high interannual variability of ecosystem C fluxes during summer and autumn was observed but the resulting effect on the annual net C budget was moderate. Increased severity and/or duration of summer drought under climate change do not appear to have the potential to negatively impact the average C budget of this ecosystem. On the contrary, factors affecting ecosystem functioning (drought and/or defoliation) during March–June period may reduce dramatically the annual C balance of evergreen Mediterranean forests.     

Phytoplankton dynamics and bloom events in oligotrophic Mediterranean lagoons: seasonal patterns but hazardous trends

Hydrobiologia - Detailed seasonal analyses of phytoplankton assemblages’ composition were performed on long-term datasets (20&nbsp;years) of two oligotrophic Mediterranean lagoons (Diana...