Regional patterns of diversity and estimates of global insect species richness

The total number of insect species in the world is an important if elusive figure. We use a fresh approach to estimate global insect species richness, based on biogeographic patterns of diversity of well or better documented taxa. Estimates generated by various calculations, all variations on a theme, largely serve to substantiate suggestions that insect species are likely to number around 10 million or less.     

New or interesting Laboulbeniales (Ascomycetes) on Japanese chlaeniine beetles (Coleoptera,Carabidae)

Four species ofLaboulbenia were isolated from Japanese chlaeniines and are reported.Laboulbenia habui is described as a new species; it is possibly related toL. fasciculata. Laboulbenia habui is characterized by the proliferation and division of cell V, resulting in the formation of an obliquely superposed series of cells from which short, cylindrical cells arise in a double row, whereas there is a single row of cubical cells inL. fasciculata. Laboulbenia humilis is new for the Japanese mycoflora; antheridia of this fungus were observed for the first time; shape of the perithecial apex, persistent antheridia and the spore size suggest thatL. humilis is not closely related toL. exigua and its related taxa. ForL. proliferans andL. fasciculata, new chlaeniine hosts are listed and some supplemental notes are given.     

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.     

Bat fly species richness in Neotropical bats: correlations with host ecology and host brain

Patterns of ectoparasite species richness in mammals have been investigated in various terrestrial mammalian taxa such as primates, ungulates and carnivores. Several ecological or life traits of hosts are expected to explain much of the variability in species richness of parasites. In the present comparative analysis we investigate some determinants of parasite richness in bats, a large and understudied group of flying mammals, and their obligate blood-sucking ectoparasite, streblid bat flies (Diptera). We investigate the effects of host body size, geographical range, group size and roosting ecology on the species richness of bat flies in tropical areas of Venezuela and Peru, where both host and parasite diversities are high. We use the data from a major sampling effort on 138 bat species from nine families. We also investigate potential correlation between bat fly species richness and brain size (corrected for body size) in these tropical bats. We expect a relationship if there is a potential energetic trade-off between costly large brains and parasite-mediated impacts. We show that body size and roosting in cavities are positively correlated with bat fly species richness. No effects of bat range size and group size were observed. Our results also suggest an association between body mass-independent brain size and bat fly species richness. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Assessing fern diversity: relative species richness and its environmental correlates in Uganda

Techniques for the rapid quantification of tropical biodiversity are of critical importance in deciding where to invest scarce conservation resources. Here we describe a simple survey method for assessing species-level richness of a poorly known plant group, the pteridophytes. We then illustrate the use of a powerful, rarefaction- based technique of controlling for inevitable differences in sampling effort to calculate the relative species richness of our study sites. Lastly, we explore how closely observed patterns of relative species richness of Ugandan forests are correlated with a suite of simple environmental variables. We find that fully 75% of the variance in our estimate of fern diversity can be predicted from just two measures: soil fertility (scored as C/N ratio, itself related to rainfall); and distance from the nearest putative Pleistocene refugium.     

Seasonal patterns in species richness of herbivores: Macrolepidopteran larvae on Finnish deciduous trees

Abstract. 1. The seasonal distribution of macrolepidopteran species richness on Finnish deciduous trees vaned from positively skewed (peak in spring) to negatively skewed (peak in autumn).
2. The skewness values of species richness had a significant negative correlation ( r = - 0.98) with the duration of the seasonal shoot-growth period of the tree species.
3. Trees which complete their shoot growth early in the season ( Quercus type) produce new leaves only during spring, while trees whose shoot growth continues to autumn ( Populus type) do so throughout the summer.
4. Consequently, there is a difference in the number of available resources in the late summer foliage of different tree species, Trees ceasing leaf production early such as oak ( Quercus robur ) and bird cherry ( Prunus padus ) have one major resource type (mature leaves) in late-season foliage while trees like birches and alders have two Ooung and mature leaves).
5. Because young leaves formed late in the season are preferred to mature ones by some species of herbivores and because other species prefer mature leaves at the same time, the species richness of Populus-type trees is higher later in the season than the species richness of Quercus-type of trees, which have just one type of resource available.     

Declines in littoral species richness across both spatial and temporal nutrient gradients: a palaeolimnological study of two taxonomic groups

1. Using a palaeolimnological approach in shallow lakes, we quantified the species richness responses of diatoms and Cladocera to phosphorus enrichment. We also examined differences in species richness responses between littoral and pelagic assemblages of our focal communities. To address both spatial and temporal relationships, our study includes an analysis of both surface sediments from 40 lakes and of a lake sediment record spanning c. 120 years. The objective of our study was to determine whether similar species richness patterns occurred across trophic levels, as well as along spatial and temporal gradients. 2. We found that both diatom and Cladocera species richness estimates significantly declined with increasing phosphorus across space and through time. When the assemblages were subdivided according to known habitat preferences, littoral biodiversity maintained a negative trend, whereas pelagic species richness tended to show no relationship with phosphorus. 3. Negative productivity–diversity patterns have been observed across almost all palaeolimnological studies that span large productivity gradients. This congruence in patterns is most likely due to the similarity in data collection methods and in focal communities studied. The contrasting responses between littoral and pelagic assemblages may be explained by the differences in physical habitat and the pool of taxa in each of these environments. Consistent with the literature, we found statistical support for the idea that littoral diversity declines could be explained by an interaction between macrophytes and nutrients along strong trophic gradients. The general lack of a diversity response in our pelagic assemblages could be attributable to the limited pool of subfossil taxa. The response of the pelagic diatom could also be related to their broad range of nutrient tolerances. 4. The observed negative response of species richness to phosphorus enrichment, particularly in the littoral assemblages, has implications for ecosystems functioning because communities with reduced biodiversity often are less resilient to anthropogenic change.     

A new species of the genus Laboulbenia (Laboulbeniales) on Ophionea indica (Coleoptera, Carabidae, Odacanthini) from Taiwan

Laboulbenia ophioneae is described as a new species with illustrations. It is closely related to Laboulbenia celestialis and Laboulbenia asiatica because of some similarities in the morphology of appendages and perithecia. The present species from the latter two species can be distinguished by the shorter, inflated perithecia, the shorter receptacles, and the appendages consisting of more or less darkly colored, broader branches. This new species was found on elytra of Ophionea indica from Taiwan, which has been also known as a host of Laboulbenia polymorpha. A mature thallus noticed by Terada (2004) on the slide 673b (M. Ishikawa collection) and a young thallus illustrated by Sugiyama (1978, fig. 1-G as L. polymorpha) on 673d (M. Ishikawa collection) are both identified as L. ophioneae.     

An exploration of factors influencing lotic insect species richness

An understanding of factors that influence species richness of lotic insects is generally lacking. We present comparative data on aquatic insect species richness from several North American and other streams. Factors such as large sample numbers and drainage area (species area relationships) are not significant predictors of species richness across the streams we examined. We explore several hypotheses regarding the origins and maintenance of species richness using Upper Three Runs Creek (UTR), South Carolina, USA, as a reference stream. UTR has the highest species richness of any stream in the Western Hemisphere. Hypotheses examined included historical, regional and local processes such as: (1) Evolutionary time, (2) disturbance regime/environmental variability, (3) temperature/evolutionary-speed, (4) productivity, and (5) habitat heterogeneity. Of these hypotheses, we suggest that productivity and habitat heterogeneity appear to contribute most to the high species richness found in UTR. We believe that multidisciplinary analysis of other streams is necessary because without this crucial information our knowledge of, and desire to protect biodiversity in streams will be wanting.     

Species richness, species range size and ecological specialisation among African primates: geographical patterns and conservation implications

The geographical distribution of species richness and species range size of African anthropoid primates (catarrhines) is investigated and related to patterns of habitat and dietary niche breadth. Catarrhine species richness is concentrated in the equatorial regions of central and west Africa; areas that are also characterised by low average species range sizes and increased ecological specificity. Species richness declines with increasing latitude north and south of the equator, while average species range size, habitat and dietary breadth increase. Relationships between species richness, species range size and niche breadth remain once latitudinal and longitudinal effects have been removed. Among areas of lowest species richness, however, there is increased variation in terms of average species range size and niche breadth, and two trends are identified. While most such areas are occupied by a few wide-ranging generalists, others are occupied by range-restricted specialist species. That conservation efforts increasingly focus on regions of high species richness may be appropriate if these regions are also characterised by species that are more restricted in both their range size and their ecological versatility, although special consideration may be required for some areas of low species richness.     

Environmental correlates of vegetation patterns and species richness in the northern Grampians,Victoria

Abstract Plant species cover-abundance and density data were collected for 94 sample plots across a gradient from rocky uplands to sandy outwash plains in the northern part of Grampians (Gariwerd) National Park in western Victoria. Detrended correspondence analysis (DCA) was used to identify dominant gradients in species composition. A range of static (e.g. substrate type, soil depth, microclimate indicators) and dynamic (e.g. elapsed time since last fire) environmental variables were measured. Correlations were sought between these variables and vegetation patterns including those for richness (R) and Shannon-Weiner diversity (H′). The dominant gradient of vegetation change identified by DCA separated rocky sites and sites near ephemeral streams, from well-drained, sandy sites. Secondary gradients identified time since last fire as important for sandy sites, and altitude and aspect-related microclimate for rocky sites. Diversity was highest in the first 2 years after fire but showed no further decline in older sites. Overall, R and H' were negatively correlated with soil nutrient concentrations. On sandy sites R was high, but was low on rocky sites and near streams. Within the rocky sites, R was highest on cool, moist south and east slopes, and lowest on hot, dry north and west slopes. Explanations of diversity patterns based on inhibition of competitive exclusion due to stress and recurrent disturbance best fit the results presented here.     

Abundance and species richness patterns of diving beetles (Coleoptera, Dytiscidae) from exposed and protected sites in 98 northern Swedish lakes

Forty species of predaceous diving beetles (Coleoptera, Dytiscidae) were collected in sweepnet samples from 98 boreal lakes in northern Sweden. Samples from protected sites with vegetation had significantly more specimens and species than those from exposed sites without vegetation in the same lakes. No geographically based differences, e.g. latitudinal or in distance from the coast, were found. These gradients were 200 and 150 km long, respectively. Species' distribution in terms of occurence at number of sites was positively correlated with the mean abundance of the species. The relationship between species' abundance and body length was characterized by the lack of large, abundant species. Partial least square regressions on dytiscid abundance and species richness showed low predictive power of lake area, altitude and water chemistry. The seven environmental variables used explained at best 15.3 and 24.4% of the total variance in abundance and species richness, respectively. The results are compared to activity trap catches of dystiscids in lakes in an adjacent region. A majority of the species occured in both materials. However, species occuring in high proportion in one of the materials, were rare in the other material. The mean body length of the species caught more efficiently with traps was not larger than that of those overpresented in net sampling. Based on this study and the available literature data, the regional species pool of boreal lake dytiscids is estimated to 30–40 species. It is still an open question if lake assemblages are markedly poorer than those found in the development of vegetation, whereas the impact of water chemistry is small.     

Concordance of species richness patterns among multiple freshwater taxa: a regional perspective

Geographical gradients in species richness and the degree to which different taxa show congruent patterns remain unknown for many taxonomic groups. Here, I examined broad-scale species richness patterns in five groups of freshwater organisms; macrophytes, dragonflies, stoneflies, aquatic beetles and fishes. The analyses were based on provincial distribution records in Denmark, Norway, Sweden and Finland. In general, variation in species richness across provinces was concordant among the groups, but stoneflies showed weaker negative relationships with the other taxonomic groups. Species richness in most groups decreased with increasing latitude and altitude, and a considerable part of the variation was explained by mean July temperature. However, stoneflies showed a reversed pattern, with species richness correlating positively, albeit more weakly, with mean provincial altitude. Nevertheless, combined species richness of all five taxa showed a strong relationship with mean July temperature, accounting for 74% of variation in provincial species richness alone. Such temperature-controlled patterns suggest that regional freshwater biodiversity will strongly respond to climate change, with repercussions for local community organization in freshwater ecosystems in Fennoscandia.     

Climate induced increases in species richness of marine fishes

Climate change has been predicted to lead to changes in local and regional species richness through species extinctions and latitudinal ranges shifts. Here, we show that species richness of fish in the North Sea, a group of ecological and socio-economical importance, has increased over a 22-year period and that this rise is related to higher water temperatures. Over eight times more fish species displayed increased distribution ranges in the North Sea (mainly small-sized species of southerly origin) compared with those whose range decreased (primarily large and northerly species). This increase in species richness can be explained from the fact that fish species richness in general decreases with latitude. This observation confirms that the interaction between large-scale biogeographical patterns and climate change may lead to increasing species richness at temperate latitudes.     

空间尺度对地形异质性-物种多样性关系的影响:粒度和幅度

空间尺度是影响我们理解生态学格局和过程的关键因素.目前已有多种关于物种多样性分布格局形成机制的假说且研究者未达成共识,原因之一是空间尺度对物种多样性分布格局的环境影响因子的解释力和相对重要性有重要影响.地形异质性是物种多样性分布格局的重要影响因素.本文综述了在地形异质性-物种多样性关系的研究中,不同空间粒度和幅度对研究...     

Geographical patterns and determinants of species richness in Mexico across selected families of vascular plants: implications for conservation

Mexico is considered a megadiverse country containing more than 10% of the world's biodiversity. The distribution of this species richness and endemism is different among the different Mexican states. We examined the species richness patterns of 13 families of vascular plants (including ferns, gymnosperms and angiosperms) in Mexico using political divisions (states) as units of analysis. We analysed the species richness values (absolute richness, endemic richness and restrictive richness) of these plant families using stepwise multiple regression analysis, assessing their relationship with a set of 10 environmental variables (expressed as heterogeneity coefficients). A combined cluster analysis with multidimensional scaling analysis (MDS) and an analysis of similarities were also undertaken to define the spatial–geographical patterns. Additionally, we proposed a methodological strategy to determine which states of Mexico have priorities for conservation. Our results suggested that the three species richness values used were significantly predicted by environmental factors, especially by climatic heterogeneity. Notwithstanding that a linear pattern was recognized, the Mexican states were gathered in four groups, which were confirmed by the MDS and the cluster analysis: (1) the Yucatan Peninsula, (2) arid Mexico, (3) the Mexican Transition Zone and (4) the megadiverse states. We proposed that 12 Mexican states include all the environmental conditions and are candidates for developing conservation programmes: (1) Quintana Roo, Tabasco and Yucatán, (2) Baja California, Chihuahua and Sinaloa, (3) Guerrero, Jalisco and Nuevo León and (4) Chiapas, Oaxaca and Veracruz.     

Latitudinal effects on treehopper species richness (Hornoptera: Membracidae)

Abstract. 1. Membracid species richness declines with increasing latitude in the Western hemisphere but begins to increase again in temperate regions. In northern latitudes this transition occurs in the highlands of Mexico and is the result of the emergence of a new tribe and greater host specialization.
2. The relationship between number of species per genus and latitude is parabolic.
3. We suggest the low number of species per genus in tropical regions may be due to the lack of host specialization and reduced coordination of life history with host phenology.     

运用稀疏法分析物种丰富度的海拔梯度分布格局:以样方实测乔木种数据为例

植物物种丰富度随山地海拔梯度的变化格局是生物多样性研究的热点之一.基于种-面积关系的任何模型对群落物种数目所作估计,其精度都依赖于样本的代表性、抽样尺度以及所涉及的分类群.作者以秦岭南坡森林群落样方实测的乔木种数据为例,借鉴群落最小面积(minimum area,MA)的概念及其确定方式,利用稀疏法(rarefacti...