Individuality and the existence of species through time

The individuality of species provides the basis for linking practical taxonomy with evolutionary and ecological theory. An individual is here defined as a collection of parts (lower-level entities) that are mutually connected. Different types of species individual exist, based on different types of connection between organisms. An interbreeding species is a group of organisms connected by the potential to share common descendants, whereas a genealogical species is integrated by the sharing of common ancestors. Such species definitions serve to set the limits of species at a moment of time and these slices connect through time to form time-extended lineages. This perspective on the nature of individuality has implications that conflict with traditional views of species and lineages: (1) Several types of connections among organisms may serve to individuate species in parallel (species pluralism); (2) each kind of species corresponds to a distinct kind of lineage; (3) although lineage branching is the most obvious criterion to break lineages into diachronic species, it cannot be justified simply by reference to species individuality; (4) species (like other individuals) have fuzzy boundaries; (5) if we wish to retain a species rank, we should focus on either the most- or least-inclusive individual in a nested series; (6) not all organisms will be in any species; and (7) named species taxa are best interpreted as hypotheses of real species. Although species individuality requires significant changes to systematic practice and challenges some preconceptions we may have about the ontology of species, it provides the only sound basis for asserting that species exist independently of human perception.     

Guadalupe Island: Lost paradise recovered? Overgrazing impact on extinction in a remote oceanic island as estimated through accumulation functions

Guadalupe Island, an oceanic island in the northwest of Mexico, is an outlier of the California Floristic Province that has been disturbed by introduced goats for more than a century, with dramatic effects of goats on plant communities and local species extinctions. In 2004 the island went through a successful eradication program. Since then, six previously unrecorded species have been discovered and four supposed extinct species have been found again. Quantifying the true species richness of the island at the time of eradication, to set a benchmark for the future monitoring of this large-scale natural experiment, is both a challenge and a necessity. For this purpose, we estimated (a) current and (b) accumulated historical plant species richness of the island through accumulation functions. Estimation of current species richness was based on the geographical accumulation process of species richness (80 species) obtained from sampling 110 (50 m × 2 m) transects distributed along the island in year 2004. Historical species richness was estimated through the temporal accumulation of species richness (119 species) from botanical records (1,960 specimens reviewed) between 1875 and 2000. The predicted value of historical richness (213 species) is similar to known historical records (218 species), but estimation of current richness (203 species) is significantly higher than accepted extant plant richness (187 species). Our results suggest that currently there may be more plant species living in the island than estimated through recent botanical exploration. Future monitoring of the island as it recovers will clarify this hypothesis.     

Trophic levels in community food webs

Summary Four concepts are considered for the trophic level of a species in a community food web. The long-way-up-level (or LU-level) of species A is the length of the longest simple food chain from a basal species (one with no prey in the web) to A. (A simple chain is a chain that does not pass through any given species more than once.) The short-way-up-level (SU-level) of species A is the length of the shortest chain from a basal species to A. The long-way-down-level (LD-level) of species A is the length of the longest simple chain from species A to a top species (one with no consumers in the web). The short-way-down-level (SD-level) of species A is the length of the shortest chain from species A to a top species. The stratigraphy of a web is the analogue for species of the pyramid of numbers for individuals: it is the frequency distribution of species according to level. The LU-, SU-, LD-, and SD-stratigraphies of the seven webs in the Briand-Cohen collection with 30 or more trophic species reveal no species with LU-level or LD-level more than 6, no species with SU-level more than 3, and no species with SD-level more than 2. In all seven webs, SD-levels are stochastically less than SU-levels: species tend to be closer to a top predator than to a basal species. Two stochastic models of food web structure (the cascade model and the homogeneous superlinear model) correctly predict that 95% or more of species should have LU-level and LD-level in the range 0–6. The models also correctly predict some details of the distribution of species in the SU- and SD-stratigraphies, particularly the fraction of species in level 1. The models do not, in general, correctly predict the distribution of species within the range 0–6 of LU-levels and LD-levels.     

The statistical mechanics of community assembly and species distribution

? Theoretically, communities at or near their equilibrium species number resist entry of new species. Such 'biotic resistance' recently has been questioned because of successful entry of alien species into diverse natural communities. ? Data on 10,409 naturalizations of 5350 plant species over 16 sites dispersed globally show exponential distributions both for species over sites and for sites over number of species shared. These exponentials signal a statistical mechanics of species distribution, assuming two conditions. First, species and sites are equivalent, either identical ('neutral') or so complex that the chance a species is in the right place at the right time is vanishingly small ('idiosyncratic'); the range of species and sites in our data disallows a neutral explanation. Secondly, the total number of naturalizations is fixed in any era by a 'regulator'. ? Previous correlation of species naturalization rates with net primary productivity over time suggests that the regulator is related to productivity. ? We conclude that biotic resistance is a moving ceiling, with resistance controlled by productivity. The general observation that the majority of species occur naturally at only a few sites, and only a few species occur at many sites, now has a quantitative (exponential) character, offering the study of species' distributions a previously unavailable rigor.     

Phylogenetic Analysis of Leymus (Poaceae: Triticeae) Inferred from Nuclear rDNA ITS Sequences

To investigate the phylogenetic relationships of polyploid Leymus (Poaceae: Triticeae), sequences of the nuclear rDNA internal transcribed spacer region (ITS) were analyzed for 34 Leymus accessions representing 25 species, together with three Psathyrostachys species (Ns genome), two Pseudoroegneria (St genome) species, Lophopyrum elongatum (E(e) genome), and Thinopyrum bessarabicum (E(b) genome). The phylogenetic analyses (maximum likelihood and Bayesian inference) supported two major clades, one including 21 Leymus species and three Psathyrostachys species, the other with nine Leymus species and four diploid species. The ITS RNA secondary structure of the Leymus species was compared with that of their putative diploid donor. It is suggested that (1) the species from the same areas or neighboring geographic regions are closely related to each other; (2) L. coreanus, L. duthiei, L. duthiei var. longearistatus, and L. komarovii are closely related to other Leymus species, and it is reasonable to transfer these species from the genus Hystrix to Leymus; (3) the ITS sequences of Leymus are evolutionarily distinct; (4) the different Leymus species and different distribution of a species derived their Ns genome from different Psathyrostachys species; and (5) there is a close relationship among Leymus, Pseudoroegneria, Lophopyrum, and Thinopyrum, but it is difficult to presume that the St, E(e), and E(b) genome may be the Xm genome donor of the Leymus species.     

Tree heterogeneity,resource availability,and larger scale processes regulating arboreal ant species richness

Abstract Processes acting on different spatial and temporal scales may influence local species richness. Ant communities are usually described as interactive and therefore determined by local processes. In this paper we tested two hypotheses linked to the question of why there is local variation in arboreal ant species richness in the Brazilian savanna (‘cerrado’). The hypotheses are: (i) there is a positive relationship between ant species richness and tree species richness, used as a surrogate of heterogeneity; and (ii) there is a positive relationship between ant species richness and tree density, used as a surrogate of resource availability. Arboreal ants were sampled in two cerrado sites in Brazil using baited pitfall traps and manual sampling, in quadrats of 20 m × 50 m. Ant species richness in each quadrat was used as the response variable in regression tests, using tree species richness and tree density as explanatory variables. Ant species richness responded positively to tree species richness and density. Sampling site also influenced ant species richness, and the relationship between tree density and tree species richness was also positive and significant. Tree species richness may have influenced ant species richness through three processes: (i) increasing the variety of resources and allowing the existence of a higher number of specialist species; (ii) increasing the amount of resources to generalist species; and (iii) some other unmeasured factor may have influenced both ant and tree species richness. Tree density may also have influenced ant species richness through three processes: (i) increasing the amount of resources and allowing a higher ant species richness; (ii) changing habitat conditions and dominance hierarchies in ant communities; and (iii) increasing the area and causing a species–area pattern. Processes acting on larger scales, such as disturbance, altitude and evolutionary histories, as well as sampling effect may have caused the difference between sites.     

浙江种子植物物种编目

生物多样性的编目和分类以及生物多样性监测是全球生物多样性研究的两个核心内容。物种编目是了解物种多样性的基础, 只有掌握物种分布格局及物种与环境的关系, 才能为物种监测和科学管理提供依据。作为浙江种子植物研究的“家底”, 本文在《浙江植物志(新编)》编研的基础上, 系统整理了浙江种子植物的物种名录。结果显示, 浙江共有种子植物212科1,469属4,430种, 其中野生植物有190科1,085属3,347种。所含种数多于100种的科有禾本科(285种)、莎草科(216种)、菊科(186种)、蔷薇科(153种)、兰科(126种)、蝶形花科(109种)和唇形科(108种); 含20种以上的属有15属, 包括薹草属(Carex, 126种)、刚竹属(Phyllostachys, 44种)、悬钩子属(Rubus, 44种)、冬青属(Ilex, 35种)、蓼属(Polygonum, 34种)、珍珠菜属(Lysimachia, 32种)、铁线莲属(Clematis, 31种)、景天属(Sedum, 28种)、槭属(Acer, 26种)、荚蒾属(Viburnum, 26种)、飘拂草属(Fimbristylis, 26种)、蒿属(Artemisia, 25种)、堇菜属(Viola, 22种)、葡萄属(Vitis, 21种)和山矾属(Symplocos, 21种)。其区系特点主要反映在: 物种丰富, 其科属组成多样; 保存了较多古老孑遗植物; 地理成分多样, 联系广泛, 由热带向温带过渡; 中国特有科2科、中国特有属45属、浙江(准)特有种近500种(含亚种和变种), 珍稀濒危植物丰富, 96种为国家重点保护植物; 外来植物多, 入侵风险大, 有些种已形成明显的危害。     

Contribution of rarity and commonness to patterns of species richness

There is little understanding in ecology as to how biodiversity patterns emerge from the distribution patterns of individual species. Here we consider the question of the contributions of rare (restricted range) and common (widespread) species to richness patterns. Considering a species richness pattern, is most of the spatial structure, in terms of where the peaks and troughs of diversity lie, caused by the common species or the rare species (or neither)? Using southern African and British bird richness patterns, we show here that commoner species are most responsible for richness patterns. While rare and common species show markedly different species richness patterns, most spatial patterning in richness is caused by relatively few, more common, species. The level of redundancy we found suggests that a broad understanding of what determines the majority of spatial variation in biodiversity may be had by considering only a minority of species.     

Macaronesian millipedes (Diplopoda) with emphasis on endemic species swarms on Madeira and the Canary Islands

Endemic species swarms constitute large fractions of the millipede faunas of Madeira (29 species of the Cylindroiulus madeirae group, plus six species of Acipes , out of a total of 60 species) and the Canary Islands (46 species of Dolichoiulus , plus four species of the Glomeris alluaudi-group , out of a total of about 79 species). The poorer faunas of the Azores (22 species) and the Cape Verde Islands (15 species) in contrast only include a few endemics. The Cylindroiulus madeirae group and Dolichoiulus show a high degree of diversity of structure (size, colour, leg length etc.) and habitat (laurisilva, xeric habitats, caves). The C. madeirae group, unlike Dolichoiulus , is strongly concentrated in the laurisilva. In this habitat, microhabitat differentiation is pronounced in both swarms.     

Revision of ilyphagus chamberlin, 1919 (polychaeta, flabelligeridae)

Ilyphagus Chamberlin, 1919 includes abyssal, fragile benthic species. Most species have large cephalic cages but chaetae are brittle and easily lost which may explain why the original definition included species with a cephalic cage or without it. The type species, Ilyphagus bythincola Chamberlin, 1919, together with another species (Ilyphagus pluto Chamberlin, 1919) were described as lacking a cephalic cage whereas a third species (Ilyphagus ascendens Chamberlin, 1919) was described with one. To clarify this situation, all available type and non-type materials were studied. Ilyphagus is redefined to include species with digitiform bodies, abundant filiform papillae and a thin body wall; their neurochaetae are thick, anchylosed aristate spines, and all species have a cephalic cage (in the type species the presence of a cage is inferred from the remaining chaetal scars). Ilyphagus pluto, which also lacks a a cephalic cage is determined here to be a holothurian. The redefined genus contains Ilyphagus bythincola (incl. Ilyphagus ascendens), Ilyphagus coronatus Monro, 1939, Ilyphagus hirsutus Monro, 1937, and Ilyphagus wyvillei (McIntosh, 1885).     

The factors controlling species density in herbaceous plant communities: an assessment

This paper evaluates both the ideas and empirical evidence pertaining to the control of species density in herbaceous plant communities. While most theoretical discussions of species density have emphasized the importance of habitat productivity and disturbance regimes, many other factors (e.g. species pools, plant litter accumulation, plant morphology) have been proposed to be important. A review of literature presenting observations on the density of species in small plots (in the vicinity of a few square meters or less), as well as experimental studies, suggests several generalizations: (1) Available data are consistent with an underlying unimodal relationship between species density and total community biomass. While variance in species density is often poorly explained by predictor variables, there is strong evidence that high levels of community biomass are antagonistic to high species density. (2) Community biomass is just one of several factors affecting variations in species density. Multivariate analyses typically explain more than twice as much variance in species density as can be explained by community biomass alone. (3) Disturbance has important and sometimes complex effects on species density. In general, the evidence is consistent with the intermediate disturbance hypothesis but exceptions exist and effects can be complex. (4) Gradients in the species pool can have important influences on patterns of species density. Evidence is mounting that a considerable amount of the observed variability in species density within a landscape or region may result from environmental effects on the species pool. (5) Several additional factors deserve greater consideration, including time lags, species composition, plant morphology, plant density and soil microbial effects.Based on the available evidence, a conceptual model of the primary factors controlling species density is presented here. This model suggests that species density is controlled by the effects of disturbance, total community biomass, colonization, the species pool and spatial heterogeneity. The structure of the model leads to two main expectations: (1) while community biomass is important, multivariate approaches will be required to understand patterns of variation in species density, and (2) species density will be more highly correlated with light penetration to the soil surface, than with above-ground biomass, and even less well correlated with plant growth rates (productivity) or habitat fertility. At present, data are insufficient to evaluate the relative importance of the processes controlling species density. Much more work is needed if we are to adequately predict the effects of environmental changes on plant communities and species diversity.     

鄂西南亚热带山地常绿落叶阔叶混交林物种多度分布格局

基于七姊妹山自然保护区内6 hm~2监测样地多度数据,通过累计经验分布曲线(ECDF)表征该样地内不同生活型功能群的物种-多度分布格局,并采用6种模型对各功能群不同取样尺度物种等级-多度曲线进行拟合并检验其拟合效果,分析多度格局与模型拟合在不同尺度间的差异,探讨其背后的生态学过程与机制。结果表明:(1)各尺度下落叶种比常绿种的物种数多,物种多样性指数更大,但个体数相对较少;不同功能群稀有种比例排序为:落叶种所有种常绿种。(2)6种模型中的断棍模型的拟合效果较差;中大尺度(50 m×50 m、100 m×100 m)上不同生活型树种多度分布能接受的模型较少,除大尺度的常绿树种外,拟合最优模型均为对数正态分布模型,大尺度的常绿树种拟合最优模型为中性模型;小尺度上(20 m×20 m)常绿树种的最优模型为对数正态分布模型,落叶树种最优模型为生态位优先模型,所有树种在小尺度最优模型为Zipf-Mandelbrot模型。研究认为,随着尺度逐渐扩大,中性过程较生态位过程对物种-多度格局的解释力度更大,落叶树种物种多度格局的形成机制较常绿树种更接近于样地所有树种物种-多度格局的形成机制。     

A new species of Anuretes Heller, 1865 (Copepoda: Caligidae) from the yellowbanded sweetlips Plectorhinchus lineatus (Haemulidae) off New Caledonia

A new species of caligid copepod, Anuretes justinei n. sp., is described from off New Caledonia. It is parasitic on the gill filaments of a haemulid fish, the yellowbanded sweetlips Plectorhinchus lineatus (Linnaeus). The new species is distinguished from its congeners by the combination of the following character states: (1) the fourth pedigerous somite is covered dorsally by the expanded free posterior margin of the cephalothorax; (2) a maxillary whip is present; (3) the relatively small genital complex is less than half the length of the cephalothorax; (4) leg 3 is armed with nine setae on the terminal exopodal segment and six setae on the terminal endopodal segment; and (5) leg 4 is long and slender with a setal armature of I, III twisted spines. The new species is an addition to the possibly monophyletic group of seven species that is characterised by the possession of a maxillary whip, all of which are found on haemulid hosts. The host-specificity of Anuretes is relatively high, its species being largely parasitic on reef-associated fishes, such as the families Haemulidae (eight species), Ephippidae (four species), Acanthuridae (four species) and Pomacanthidae (one species).     

Body size and resource partitioning in ladybirds

[First paragraph]Resource utilisation is usually viewed in terms of food species size (Schoener, 1974) with each species in a predator guild adapted to exploit a particular-sized species of prey. Large species of predators exploit large species of prey and vice versa. That is, each species in a guild is able to displace other species from a particular portion of the resource space by virtue of it being better adapted to exploit that particular species of prey in that resource space.     

Ignoring ecological demands masks the real effect of urbanization: a case study of ground-dwelling spiders along a rural–urban gradient in a lowland forest in Hungary

We studied ground-dwelling spiders along a rural?Csuburban?Curban forest gradient representing increasing human disturbance using pitfall traps. We tested four known and two novel hypotheses: (1) increasing disturbance hypothesis (species richness is decreasing by disturbance); (2) matrix species hypothesis (the richness of open-habitat species is increasing by disturbance); (3) opportunistic species hypothesis (the richness of generalist species is increasing by disturbance); and (4) habitat specialist hypothesis (the number of the forest specialist species is decreasing by disturbance). As a consequence of urbanization, urban forests become drier and more open; thus, according to the new hypotheses, the number of (5) xerophilous species and (6) light-preferring species are increasing in the urban area. Our result did not support the increasing disturbance hypothesis, as the overall species richness increased from the rural sites to the urban ones. As predicted, the number of both the open-habitat and the generalist species increased towards the urban sites. The number of forest specialist species was higher in the suburban area than in the rural and urban area. Both xerophilous and light-preferring species were the most numerous in the urban area, supporting the xerophilous species and the light-preferring species hypotheses. Canonical correspondence analysis showed that the forest specialist species associated with the rural sites with higher amounts of decaying woods and more herbs or with the suburban sites with higher cover of leaf litter and higher relative humidity. Two generalist species and one open-habitat species were characteristic of urban sites with higher ground surface and air temperature.     

毛茛科金莲花亚科植物的地理分布

本文对毛茛科金莲花亚科各属的地理分布作了分析,该亚科植物除了少数属的一些种分布到南半球的温带地区,一些种分布或延伸到亚热带山地、非洲东部和北部的干旱、半干旱的地区外,绝大部分的属、种均分布于泛北极区域。根据其17个属的地理分布式样,把它们划分为8个分布区类型:(1)北温带分布类型4属;(2)北温带和非洲分布类型1属;(3)北半球温带和南半球间断分布类型1属;(4)欧洲和东亚间断分布类型1属;(5)西亚分布类型1属;(6)地中海分布类型3属;(7)欧亚和温带亚洲分布类型1属;(8)东亚分布类型5属。本文以形态特征为主,结合花粉和染色体的性状分析,认为东亚特有的鸡爪草属、Megaleranthis和铁破锣属可能分别是联系驴蹄草属和金莲花属,鸡爪草属和金莲花属以及金莲花族和升麻族的中间类型。另外,文中详细地统计了该亚科的不同等级分类群及特有种在各个植物区的分布,并从系统发育的观点讨论了各个植物区所具有的原始类群和进化类群,提出了如下论点,即东亚植物区(特别是中国西南部)不但是金莲花亚科植物分布的多度和多样性中心以及特有类群的分布中心,而且还是原始类群的保存中心,伊朗-土兰区及地中海周围是第二分布中心。     

The effect of developmental variation on hybridization and rarity in Stipoid grasses

Developmental variation in some Achnatherum species was evaluated for two kinds of groups, (1) species pairs that do or do not hybridize and (2) rare and common species. Variation was assessed in two different ways, one that captures developmental events expressed in an individual and one reflecting developmental events that are part of the information systems of a species. The former captures the effect of the environment on development; the latter expresses developmental variation without the information controlling ontogenetic events being filtered through the environment. Development variation is lower for species pair that hybridizes when the effect of development in an individual is expressed. When that variation is of the species information system, the non-hybridizing species pair shows a lower level of developmental variation, likely the effect of greater similarity between those species. It is lower for rare species when variation in development is that of the information system of a species. The lower level of developmental variation seen in species pairs that hybridize likely reflects the necessity of compatible developmental programs in order for a hybrid to appear. Lower variation in development in rare species is expected. Here, though, the lower variation is a property of the species and not of the environment.     

A comparative study of the relationship between host size and brood size in Apanteles spp. (Hymenoptera: Braconidae)

ABSTRACT. 1. Current models of insect oviposition predict that clutch size in parasitoids should correlate with host size, with a continuum from solitary species at one end to large gregarious broods at the other. This prediction is tested for the genus Apanteles (sensu lato).
2. The distribution of brood sizes in Apanteles is bimodal, with peaks at one (solitary species) and at about twenty (gregarious species).
3. Brood size of gregarious species correlates with host size, but when a measure of the total volume of a parasitoid brood is plotted against host size, solitary species do not lie on the same regression slope as gregarious species.
4. There is a relative shortage of gregarious species on small hosts, and a relative excess of solitary species on large hosts. Solitary species on large hosts do not fully consume the host resource.
5. The possible role of evolutionary constraints to adaptive progeny allocation in Apanteles is discussed.     

Contribution of rarity and commonness to patterns of species richness in biogeographic transitions regions: Woody plants of Uruguay

There is a growing body of evidence suggesting that widespread (i.e. common) rather than geographically restricted species (i.e. rare) shape the overall distribution patterns of species richness. This is a non‐intuitive fact, given that local and regional assemblages are normally composed by numerous rare species and few common ones. We evaluated here the primacy of common species in a biogeographic transition zone, where rarity has frequently a higher incidence. We analysed the geographical variability of trees and shrubs in Uruguay, located in a transitional zone between prairie and forest biomes, to assess the relative contribution of rare and common species to the generation of richness patterns. The distribution of 301 species of the native woody assemblage of Uruguay was mapped over the national grid system (302 quadrants of approximately 22 × 30 km), using published data and herbarium records. The overall assemblage was segregated into four subassemblages in function of species distribution (quartiles). Species richness in the four quartiles was positively correlated with overall richness, but common species (quartile 3) showed the highest level of correlation. Then, we ranked species from the most widespread to the most restricted (common‐to‐rare) and from the most restricted to the most widespread (rare‐to‐common). Along each stage of the sequences we obtained a series of species richness patterns for increasing numbers of species. Correlating the species richness pattern for each subassemblage of both sequences with that of the full assemblage, we also found higher correlations in the common‐to‐rare sequence. We conclude the Uruguayan woody plants assemblage has a very large number of rare species as expected for a transitional biogeographical zone, but it was the common species that contributed most to the overall pattern of species richness. We propose the low contribution of rare species is explained by the most interspecific variability in ecological determinants within the assemblage of rare species. Therefore the spatial covariance among rare species is low, and so is the relationship with overall species richness.