稀有种和常见种对植物群落物种丰富度格局的相对贡献

物种丰富度格局的形成不仅依赖于群落的构建过程, 同样也依赖于群落中的物种组成(如稀有种和常见种)。本文以黄土高原子午岭林区的辽东栎(Quercus wutaishanica)林为研究对象, 根据频度大小对物种进行排序, 形成稀有-常见种和常见-稀有种两条物种序列, 通过逐一添加(去除)物种, 分析引起的总体物种丰富度及其成分(α多样性和β多样性)的变化, 确定稀有种和常见种对物种丰富度格局的相对贡献。结果表明: (1)常见-稀有种序列与群落总体物种丰富度的相关性呈先剧增后平稳的对数增长曲线, 而稀有-常见种序列与群落总体的相关性与前者刚好相反, 呈先平稳后剧增的指数增长曲线; (2) α多样性在常见-稀有种序列中呈明显的对数变化曲线, 而在稀有-常见种序列中呈指数增长曲线; (3)与α多样性变化相反, β多样性在常见-稀有种序列中随物种的进入先迅速降低后逐渐平稳, 而在稀有-常见种序列中先平稳后急剧降低。可以看出, 常见种不仅主导群落的总体物种丰富度格局, 同时也是α多样性和β多样性格局的重要贡献者。因此, 常见种是群落物种丰富度格局的指示者, 也应该是优先保护的物种。     

Floristic description and ecological characteristics of the plants of Pashat Valley,Pak-Afghan border,district Bajaur,Pakistan

This study was conducted during 2018–19 to evaluate the floristic composition and ecological characteristics of vegetation of Pashat valley, Bajaur. Floristic list of the valley contains 385 species distributed in 291 genera and 102 families. The dicotyledons having 83 families with 311 species and monocotyledons with 12 families contains 61 species. Pteridophytes having 05 families with 11 species and gymnosperm with a single family of two species. The leading family was Asteraceae with 42 species (10.90%) followed by Poaceae with 39 species (10.10%), Papilionaceae (Fabaceae) with 24 species (6.23%), Lamiaceae with 20 species (5. 19%) and Rosaceae with 15 species (3.90%). Therophytes 180 species (46.80%), hemicryptophytes 53 species (13.80%), nanophanerophytes 51 species (13.20%) and geophytes 35 species (9.09%) were the dominant life form groups. Leaf size class was dominated by microphylls (138 species, 35.84%) followed by nanophylls (124 species, 32.21%) and mesophylls (89 species, 23.12%). Habit wise the vegetation was mostly herbs (289 species) followed by shrubs (54 species), trees (38 species) and lianas (4 species). According to flowering phenology, most plants (62.30%) bloomed in spring followed by in summer (34%), in autumn (1.82%), in the whole year (1.30%) and in winter (0.52%). Based on chorological affinities, most of the species were bioregional in distribution (170 species, 44.15%) followed by mono-regional (157 species, 40.78%), pluri-regional (43 species, 11.17%) and cosmopolitan (15 species, 3.89%). The ecological characteristics like life form and leaf size spectra of the vegetation have a strong correlation with the prevailing environmental conditions such as altitude, slope, precipitation and temperature.     

南亚热带森林常见种和偶见种的功能多样性特征

群落特征可能取决于物种在功能实体功能特征的独特组合（FE）中的分布。了解这些分布是保护生物多样性和维持生态系统功能的基础。鼎湖山南亚热带常绿阔叶林群落物种丰富,根据物种的多度来区分常见种（每hm²超过一个个体）和偶见种（每hm²少于一个个体）。基于功能实体,分别计算功能实体数量、功能冗余度、功能脆弱度和功能过度冗余度来描述每个样方中常见种和偶见种的功能多样性。采用Wilcoxon检验检测常见种和偶见种功能性状的差异,通过线性回归分析常见种和偶见种的功能多样性与物种数量的关系,采用冗余分析（RDA）影响常见种和偶见种的功能多样性的环境因子。研究结果表明：（1）鼎湖山南亚热带常绿阔叶林群落中功能性状在常见种和偶见种间差异显著。（2）群落中数量较低的偶见种保持着较高比例的功能实体数量。功能实体数量、功能冗余度与常见种和偶见种数量显著正相关,功能过度冗余度与偶见种数量显著正相关,功能脆弱度与常见种和偶见种的物种数量呈显著负相关。（3）海拔是影响常见种功能多样性最关键的地形因子,凹凸度是影响偶见种功能多样性最关键的地形因子。土壤含水量是影响常见种功能多样性最关键的土壤因子,速效钾是影响偶见种功能多样性最关键的环境因子。研究结果表明,尽管物种丰富的热带森林具有较高的功能冗余,但其提供的保险效应不能抵消生态系统的功能脆弱性。减少具有独特功能实体和偶见种的损失是避免热带森林生态系统功能损失的有效和必要的方法。     

Hydromedusae of the Mediterranean Sea

Mediterranean hydromedusae can be classified in several categories: common species, widely distributed throughout the Mediterranean and rare species reported from the Pacific, Indian or Atlantic Oceans; seasonal species comprising cold-season species with a boreal affinity and warm-season species with a hot to temperate affinity; neritic and mid-ocean species; surface species and meso-, infra-, and bathypelagic species. Holoplanktonic species are known to be associated with stable hydrological conditions (offshore waters, deep waters, summer and winter homothermy), whereas meroplanktonic species are more likely to be found in more disturbed hydrological conditions (coastal waters, surface waters, spring and autumn periods of temperature fluctuation). A general pattern of medusa distribution is established based upon comparative study throughout the Mediterranean.     

湖南壶瓶山国家级自然保护区蝶类区系组成及垂直分布的初步研究

2006年对湖南壶瓶山国家级自然保护区的蝶类资源进行了专题调查,共采集到蝴蝶标本1050号,初步鉴定出134种,结合文献资料记载,共记录了153种,隶属于10科85属。蛱蝶科为优势科,计30属(占35.29%)61种(39.87%)。区系成分以东洋界种类为主,计79种(51.63%),广布种60种(39.22%),而古北界种类仅14种(9.15%)。蝶类呈4个垂直带分布,但主要(88.01%)分布于海拔1100 m以下的常绿阔叶林带。多数蝴蝶适应范围比较窄,仅分布于某一垂直带内。在科级水平上,粉蝶科、眼蝶科和蛱蝶科中具多带种较多,是当地广布类群。     

Effect of species richness and relative abundance on the shape of the species accumulation curve

Abstract We explain how species accumulation curves are influenced by species richness (total number of species), relative abundance and diversity using computer‐generated simulations. Species richness defines the boundary of the horizontal asymptote value for a species accumulation curve, and the shape of the curve is influenced by both relative abundance and diversity. Simulations with a high proportion of rare species and a few abundant species have a species accumulation curve with a low ‘shoulder’ (inflection point on the ordinate axis) and a long upward slope to the asymptote. Simulations with a high proportion of relatively abundant species have a steeply rising initial slope to the species accumulation curve and plateau early. Diversity (as measured by Simpson's and Shannon–Weaver indices) for simulations is positively correlated with the initial slope of the species accumulation curve. Species accumulation curves cross when one simulation has a high proportion of both rare and abundant species compared with another that has a more even distribution of abundance among species.     

Effects of plant invasions on the species richness of abandoned agricultural land

While exotic plant invasions are thought to lead to declines in native species, the long-term impacts of such invasions on community structure are poorly known. Furthermore, it is unknown how exotic plant invasions compare to invasions by native species. We present data from 40 yr of continuous vegetation sampling of 10 fields released from agriculture to examine the effects of invasions on species richness. The effects of both exotic and native species invasions on species richness were largely driven by variations among fields with most species not significantly affecting species richness. However, invasion and dominance by the exotics Agropyron repens, Lonicera japonica. Rosa multiflora. Trifolium pratense and the native Solidago canadensis were associated with declines in richness. Invasions by exotic and native species during old field succession have similar effects on species richness with dominance by species of either group being associated with loss of species richness. Exotic species invasions tended to have stronger effects on richness than native invasions. No evidence was found of residual effects of invasions because the impact of the invasion disappeared with the decline of the invading population. When pooled across species, heavy invasion by exotic species resulted in greater loss o species richness than invasion by native species. Studies of invasion that utilize multiple sites must account for variability among sites. In our study, had we no included field as a factor we would have incorrectly concluded that invasion consistently resulted in changes in species richness.     

江西省资溪县马头山蕨类植物区系

马头山蕨类植物区系由 3 0科 62属 1 42种组成。区系地理成份复杂 ,科属的地理成份以热带亚热带性质为主。主要的科是鳞毛蕨科 (2 5种 )、水龙骨科 (1 8种 )、金星蕨科 (1 5种 )、卷柏科 (1 1种 )、蹄盖蕨科 (1 1种 ) ,5科占总种数 5 6.3 4%。主要的属是鳞毛蕨属 (1 6种 )、卷柏属 (1 1种 )、凤尾蕨属 (8种 )、铁角蕨属 (8种 )、复叶耳蕨属 (5种 )、假瘤蕨属 (4种 )占总种数 3 6.62 %。马头山蕨类植物区系属的地理成份可分为 8个 ,主要是泛热带 (1 9属 )、热带亚洲 (7属 )、世界广布 (1 9属 )成份 ,占总属数 72 .5 8%。而种的地理成份则以亚热带山地成份为主 ,本区东亚成份突出 ,加上中国特有成份共占总种数的 66.2 1 %。显然应是东亚植物区系的一部分。掌叶假瘤蕨为江西省首次发现。     

云南毛翅目昆虫区系研究

云南已知毛翅目昆虫２４科７７属３２１种,含云南特有种１５２种。其中东洋界分布成分占８３％,东洋－古北界东部共布成分占９％,东洋－古北界西部共布、东洋－非洲界共布和广布成分所占比例均小于４％。云南毛翅目在我国的分布以西南型（４４％）、华南型（２１％）和西南－华南共布型（９％）为主,其次为向东扩散的西南－华南－华中（５％）和华南－华中（４％）共布型。云南与毗邻省四川的毛翅目区系关系最密切,其次是西藏和     

Rarity, commonness, and patterns of species richness: the mammals of Mexico

Aim To determine whether rare or common species contribute most to overall patterns of spatial variation in extant species richness. Location Mexico. Methods Using data on the distribution of mammal species across Mexico at a quarter degree resolution, we ranked species from the most widespread to the most restricted (common‐to‐rare) within the study area, and from the most restricted to the most widespread (rare‐to‐common), and generated a sequence of patterns of species richness for increasing numbers of species. At each stage along both series of richness patterns, we correlated the species richness pattern for the subassemblage with that of the full assemblage. This allows comparison of subassemblages of the n most common with the n most rare species, in terms of how well they match the full assemblage richness pattern. Further analyses examined the effects on these patterns of correlation of the amount of raw information contained in the distributions of given numbers of rare and common species. Results For the mammals of Mexico the more widely distributed species contribute disproportionately to patterns of species richness compared with more restricted species, particularly for non‐volant species and endemic species. This is not simply a consequence of differences in the volumes of information contained in the distributions of rare and common species, with the disproportionate contribution of common species if anything being sharpened when these differences are taken into account. The pattern is most clearly demonstrated by endemic species, suggesting that the contribution of common species is clearest when the causes of rarity and commonness are limited to those genuinely resulting in narrow and widespread geographical ranges, respectively, rather than artificial (e.g. geopolitical) boundaries to the extents of study regions. Conclusions Perhaps surprisingly, an understanding of the determinants of overall patterns of species richness may gain most from consideration of why common species occur in some areas and are absent from others, rather than consideration of the distributions of rare species.     

A comparative study of the distribution and density of stomata in the British flora

The distribution of stomata over both leaf surfaces may affect both the photosynthetic rate and water use efficiency of species, implying that species with different photosynthetic and water requirements may also have different stomatal distributions. A database containing data on the distribution of stomata on the leaves of 469 British plant species was used to look for relationships between stomatal distribution (including both location on the leaf and density) and both habitat and morphological variables. Statistical models were applied to the data that minimized any effects that phylogenetic constraints may have had on the data.
Hypostomaty is common in woody species, species which typically occur in shaded habitats and species with large or glabrous leaves. Amphistomaty, however, predominates in species which occur in non-shaded habitats, species with small, dissected or hairy leaves, and in annual species. Amphistomaty, therefore, tends to occur in species where CO₂ may be limiting photosynthesis (unshaded environments), or where there are structures to prevent water loss from the leaf (e.g. hairs). Hypostomaty, however, occurs in slow-growing species (e.g. trees), species with leaves which have large boundary layers (large or entire leaves) and in species where CO₂ is unlikely to limit photosynthesis (shaded habitats).     

A phylogenetically controlled analysis of the roles of reproductive traits in plant invasions

Reproductive traits are tightly linked to plant fitness and may therefore be mechanisms driving biological invasions, including the greater success of more phylogenetically novel introduced species in some systems. We present a phylogenetic comparative analysis of “Baker’s law’’, that introduced plants with the ability to reproduce autogamous or asexually may be better able to establish on introduction. We gathered data from both published and unpublished sources on pollen limitation of 141 species, including 26 introduced species and 115 native species. Our analysis compared differences in the proportion of autonomous autogamy, asexual reproduction, and pollen limitation among native, introduced noninvasive, and introduced invasive plant species, and included the phylogenetic novelty of the introduced species to the native species in that community. Introduced species were more likely to be autogamous than native species, consistent with Baker’s law. On the other hand, introduced species were less likely to have the ability to reproduce asexually. Further, among species with no autonomous autogamy, pollen limitation was greater for introduced compared to native species. Such a result is consistent with the idea that plants entering a new continent receive lower quality or quantity of services from resident pollinators than species native to that continent. Finally, more phylogenetically novel invasive species had lower pollen limitation than less novel invasive species, potentially because they experience less competition for pollinators. This is the first evidence that enhanced pollination may be one mechanism driving the greater invasiveness of phylogenetically novel introduced species observed in some systems.     

Forest vascular plants as indicators of plant species richness: A data analysis of a flora atlas from northwestern Germany

Abstract

Our study had the objective to examine whether the number of forest vascular plants in a forest-poor region may be indicative of total plant species richness and of the number of threatened plant species. We also related forest plant species richness to geological and soil variables. The analysis was based on a regional flora atlas from the Weser-Elbe region in northwestern Germany including incidence data of species in a total of 1109 grid cells (each ca. 2.8 × 2.8 km²). All taxa were classified either as forest or non-forest species. Total species richness in the grid cells ranged from 65 to 597, with a mean value of 308. The number of forest species varied between 20 and 309 (mean 176). Grid cells with or without particular geological units differed in total and forest species richness, with those containing peatland and marshland being particularly species-poor. Indicator value analysis showed that both total and forest species richness in the grid cells were related to soil acidity and nitrogen in a hump-backed manner, with the highest number of species found at moderately low values for nitrogen and at intermediate values of pH. Forest species richness was highly positively correlated with the number of non-forest species and threatened non-forest species. Indicators for high species richness were primarily those species that are confined to closed semi-natural forests with a varied topography and relatively base- and nutrient-rich soils. Grid cells including historically ancient forest exhibited a higher species richness than grid cells lacking ancient forest, indicating the importance of a long habitat continuity for a high phytodiversity. The “habitat coincidence” of high species richness is best explained by similar responses of forest species and species of other habitats to the main environmental gradients. It is suggested that the regional patterns found for the Weser-Elbe region can be transferred also to other forest-poor regions in Central Europe.     

The effect of the taxon and geographic range size of host eucalypt species on the species richness of gall-forming insects

Abstract This field study was designed to test whether the taxonomic group and geographic range size of a host plant species, usually found to influence insect species richness in other parts of the world, affected the number of gall species on Australian eucalypts. We assessed the local and regional species richness of gall-forming insects on five pairs of closely related eucalypt species. One pair belonged to the subgenus Corymbia, one to Monocalyptus, and three to different sections of Symphyomyrtus. Each eucalypt pair comprised a large and a small geographic range species. Species pairs were from coastal or inland regions of eastern Australia. The total number of gall species on eucalypt species with large geographic ranges was greater than on eucalypt species with small ranges, but only after the strong effect of eucalypt taxonomic grouping was taken into account. There was no relationship between the geographic range size of eucalypt species and the size of local assemblages of gall species, but the variation in insect species composition between local sites was higher on eucalypt species with large ranges than on those with small ranges. Thus the effect of host plant range size on insect species richness was due to greater differentiation between more widespread locations, rather than to greater local species richness. This study confirms the role of the geographic range size of a host plant in the determination of insect species richness and provides evidence for the importance of the taxon of a host plant.     

黄河三角洲国家级自然保护区植物区系研究

对黄河三角洲国家级自然保护区的植物区系进行了研究分析,该区系具有以下特点：组成植物区系成分的种类比较少,计有43科,123属,193种,温带性质明显,温带分布型属占总属数的54．7％,植物成分以草本植物为主,自然分布的木本植物只有草麻黄（Ephedra sinica),柳（Salix matsudana),杞柳（S.integra),柽柳（Tamarix chinensis),单叶蔓荆（Vitex trifolia var.simplicifolia)等少数几种,植物成分中盐生物种类比较丰富,计有73种,占总种数的37．8％,植物成分中湿生,水生植物种类丰富,计有92种,占总种数的47．7％,属于比较典型的湿地生态系统。     

Decline of Mammal Species Diversity Along the Yungas Forest of Argentina

The southernmost extension of tropical Andean–Amazonian forests protrudes into the arid to semiarid habitats in northwestern Argentina. We analyzed the decline of species richness of forest mammals along these Yungas forests. In particular, we tested whether species decline is due to a general latitudinal effect and whether the drop of species from the assemblages was independent from species' traits and environmental variables. For these tests, we estimated the geographic range edges of 39 species of forest mammal and estimated the species richness with bands of 30'. First, we compared the slope of the decline of species richness from north to south (5.8 species/degree) with the decline expected from the latitudinal species gradient (1–3 species/degree). The decline in species richness of forest mammals along the Yungas was significantly steeper than expected. Second, with a null model assuming a random drop of mammal species we derived confidence limits for the expected species richness and number of range edges within the bands. None of the forest mammals reached the tip of the forest, in marked contrast to nonforest mammals. More range edges than expected from the null model fell within the bands 23°30'–24°00' S and a band near the tip of the Yungas indicating a nonrandom drop of species. The correlation between vulnerability traits and range edges suggests that processes associated with the availability of resources influence the drop of species. We propose that a suite of macroecological attributes interacting with a decrease in habitat quality determines the pattern of species richness in the Yungas forest.     

Preliminary ethnobotanical survey of kurupukari: An amerindian settlement of Central Guyana

A preliminary assessment of the utilization of plant species was undertaken within an Amerindian community at Kurupukari, Guyana. A total of 120 plant species of 46 plant families, covering 246 different plant uses were identified. Plant uses were divided into six utilization categories; 64 species for medicinal, 53 for technological, 43 edible, 20 for timber, 14 for construction and two species with miscellaneous uses. Of the 120 plant species, one species was recorded with five different use categories, two with four and 13 with three. A further 23 species were identified as having multiple uses. Of the 20 commercial timber species, five species were also shown to exhibit some form of non-timber product use, emphasising the under-utilization of species extraction. The dual extraction of both timber and non-timber resources from the same tree as a more effective sustainable utilization of available forest resources is also discussed.     

The functional trait space of tree species is influenced by the species richness of the canopy and the type of forest

Analysing how species modify their trait expression along a diversity gradient brings insight about the role that intraspecific variability plays over species interactions, e.g. competition versus complementarity. Here, we evaluated the functional trait space of nine tree species dominant in three types of European forests (a continental‐Mediterranean, a mountainous mixed temperate and a boreal) growing in communities with different species richness in the canopy, including pure stands. We compiled whole‐plant and leaf traits in 1719 individuals, and used them to quantify species trait hypervolumes in communities with different tree species richness. We investigated changes along the species richness gradient to disentangle species responses to the neighbouring environment, in terms of hypervolume size (trait variance), shape (trait relative importance) and centroid translation (shifts of mean trait values) using null models. Our main results showed differences in trait variance and shifts of mean values along the tree diversity gradient, with shorter trees but with larger crowns in mixed stands. We found constrained functional spaces (trait convergence) in pure stands, suggesting an important intraspecific competition, and expanded functional spaces (trait divergence) in two‐species admixtures, suggesting competition release due to interspecific complementarity. Nevertheless, further responses to increasing species richness were different for each forest type, waning species complementarity in sites with limiting conditions for growth. Our results demonstrate that tree species phenotypes respond to the species richness in the canopy in European forests, boosting species complementarity at low level of canopy diversity and with a site‐specific pattern at greater level of species richness. These outcomes evidence the limitation of functional diversity measures based only on traits from pure stands or general trait database values.     

Historical legacies and ecological determinants of grass naturalizations worldwide

The global distribution of exotic species is the result of abiotic, biotic and dispersal filtering processes that shape the movement and success of species outside their native range. In this study we aim to understand how these filtering processes drive the fluxes of grass species among regions, the factors that influence which species establish outside of their native range, and where they do so. We used national and subnational checklists of native and introduced grass species to determine the extent to which each region was a source or recipient of exotic grass species. We asked how species traits may distinguish those grass species that have naturalized outside their native range from those that have not, and how environmental conditions are related to the distribution of exotic grass species. We found that exotic grass establishment is shaped by an array of factors including characteristics of regions, traits of species and their interactions. Regions with a longer history of human occupation and larger numbers of native grass species were generally the most important sources of exotic species. Global flows of species were mostly driven by a climate match between the native and exotic ranges, but were also highly asymmetric, with regions with recent human arrival being the major hosts of exotic grass species. Tall, annual and C4 grass species exhibited particularly high probabilities of establishment outside their native range. Despite the idiosyncrasy and stochasticity characteristic of exotic species establishment, this biogeographical analysis revealed important generalities across this large plant group. Our results suggest that grass species that have co-occurred with humans for a longer time may be better adapted to living in anthropogenic landscapes, explaining the global asymmetry in species introductions.