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Duelli, P., Obrist, M.K. (2003) Biodiversity indicators: the choice of values and measures. Agriculture, Ecosystems and Environment. 98:87-98

Ideally, an indicator for biodiversity is a linear correlate to the entity or aspect of biodiversity under evaluation. Different motivations for assessing entities or aspects of biodiversity lead to different value systems; their indicators may not correlate at all. For biodiversity evaluation in agricultural landscapes, three indices are proposed, each consisting of a basket of concordant indicators. They represent the three value systems ÒconservationÓ (protection and enhancement of rare and threatened species), ÒecologyÓ (ecological resilience, ecosystem functioning, based on species diversity), and Òbiological controlÓ (diversity of antagonists of potential pest organisms). The quality and reliability of commonly used indicators could and should be tested with a three-step approach. First, the motivations and value systems and their corresponding biodiversity aspects or entities have to be defined. In a time consuming second step, a number of habitats have to be sampled as thoroughly as possible with regard to one or several of the three value systems or motivations. The third step is to test the linear correlations of a choice of easily measurable indicators with the entities quantified in the second step. Some examples of good and bad correlations are discussed.
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Duelli, P., Obrist, M.K. (2003) Regional biodiversity in an agricultural landscape: the contribution of seminatural habitat islands. Basic and Applied Ecology. 4:129-138

An important goal of ecological compensation measures in agricultural areas is the conservation and enhancement of regional species diversity. However, some current European agri-environment schemes seem to be rather ineffective. A likely explanation is the lack of source populations in intensely cultivated landscapes. Remnants of natural and seminatural habitats can contribute to regional biodiversity in various ways: as essential habitats for specialised species, as stepping stones, and as temporary habitats for hibernation, larval development, or preovipository feeding. The overall percentage of arthropod species, for which seminatural habitats are an essential prerequisite for living in an agricultural landscape, was assessed with a 5 km long transect of 18 standardised trapping stations. The transect extended from an isolated area of wetland through intensely managed crop fields and grassland to an isolated semiarid meadow bordered by mixed forest. For more than 1000 arthropod species the spatial and temporal distribution of a one year's catch along the transect was interpreted with regard to their affinity to seminatural habitats. Experts were asked to judge questionable cases of apparent ubiquist species. All in all, more than 63% of all animal species (except for soil and water fauna) living in the agriculturally managed areas of the Limpach valley seem to depend on the presence of seminatural habitats. We conclude that remnant islands of natural or seminatural habitats provide the most important source populations for agri-environment schemes in order to enhance biodiversity in an otherwise depleted agricultural landscape.
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Henry, C.S., Brooks, S.J., Duelli, P., Johnson, J.B. (2003) A lacewing with the wanderlust: the European song species 'Maltese', Chrysoperla agilis, sp.n., of the carnea group of Chrysoperla (Neuroptera : Chrysopidae). Systematic Entomology. 28:131-147

A fifth European member of the Holarctic carnea sibling species group, Chrysoperla agilis , sp.n. is described. This species was initially recognized because of its unique song phenotype. Both sexes produce one type of song, characterized by a single very long volley averaging 4.5 s in duration and repeated every 9.5 s. The unit of exchange during heterosexual duets (the shortest repeated unit) is the single volley. The carrier frequency is upwardly, then downwardly, modulated during each volley. The maximum frequency is higher (around 110 Hz) than in other members of the carnea group. Each volley ends with an audible, percussive 'rattle'. Song features vary only slightly over a large geographical range that extends from northern Iran westward to the Azores and northward to southern Switzerland. Discriminant function analysis confirms the uniqueness of the C. agilis song in comparison with nine other song species. Morphologically, the adult of C. agilis is very similar to C. carnea and C. pallida and is generally intermediate between them with respect to the size of the pretarsal basal dilation, the shape of the genital lip and chin, the colour and type of setae on the abdomen, and colour markings on the head and mouthparts. No single feature will distinguish C. agilis from either C. carnea or C. pallida , but a suite of physical attributes can be used with reasonable success. Larval morphology fails to distinguish clearly C. agilis from other song species. Ecologically, C. agilis shares an affinity for low vegetation with C. lucasina and C. carnea , and a preference for milder, Mediterranean climates with C. mediterranea . Adults undergo a colour change to pale yellowish brown during winter diapause, and eggs are laid singly rather than in groups. Based on its ecological characteristics, C. agilis may prove to be an effective agent of biological control in the agricultural fields of warmer, drier parts of southern Europe and the Middle East, where other members of the carnea group are less common or absent.
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Klemola, T., Hanhimaki, S., Ruohomaki, K., Senn, J., Tanhuanpaa, M., Kaitaniemi, P., Ranta, H., Haukioja, E. (2003) Performance of the cyclic autumnal moth, Epirrita autumnata, in relation to birch mast seeding. Oecologia. 135:354-361

The mast depression hypothesis has been put forward to explain the 9- to 10-year population cycle of the autumnal moth (Epirrita autumnata; Lepidoptera: Geometridae) in northern Fennoscandia. We analysed long-term data from Finnish Lapland in order to evaluate the critical assumption of the mast depression hypothesis: that better individual performance of herbivores, followed by high annual growth rate of populations, occurs in the year following mast seeding of the host, the mountain birch (Betula pubescens ssp. czerepanovii). Since mast seeding has been suggested to occur at the expense of chemical defence against herbivores, we bioassayed the quality of birch leaves from the same trees by means of yearly growth trials with autumnal moth larvae. We also measured the size of wild adults as a determinant of potential fecundity of the species in different years. The relative growth rate of larvae was poorer in post-mast years compared to other years, rather than better as assumed by the hypothesis. Conversely, a slight indication of the increase in potential fecundity was observed due to the somewhat larger adult size in post-mast years. Population growth rate estimates, however, showed that the increase in fecundity would have to be much higher to facilitate population increase towards a cyclic peak with outbreak density. Accordingly, our two data sets do not support the assumption of a higher annual growth rate in autumnal moth populations subsequent to mast seeding of the host, thereby contradicting the predictions of the mast depression hypothesis. Temperatures, when indexed by the North Atlantic Oscillation and accumulated thermal sums, were observed to correlate with the abundance or rate of population change of the autumnal moth. The factors underlying the regular population cycles of the autumnal moth, however, remain unidentified. Overall, we suggest that the causal agents in cyclic insect population dynamics should be clarified by field experimentation, since trophic interactions are complex and are further modified by abiotic factors such as climate.
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Senn, J., Suter, W. (2003) Ungulate browsing on silver fir (Abies alba) in the Swiss Alps: beliefs in search of supporting data. Forest Ecology and Management. 181:151-164

European silver fir (Abies alba Mill.) is the most heavily browsed of the commercially important tree species in montane forests of central and southeastern Europe. There are widespread reports that, for decades, fir regeneration has been poor or has even failed completely. Almost unanimously, browsing ungulates are considered the major cause. We review the scientific evidence for the role of ungulate herbivory in silver fir population dynamics, and use silver fir as a model species to highlight shortcomings in understanding and handling of the problem, with an emphasis on the Swiss situation. (1) Abundance and distribution of mature silver fir today reflect mainly a variable history of the silvicultural value of the species, and do not necessarily provide a standard for target values in today's close-to-nature silviculture. (2) Evidence for the strong impact of ungulate herbivory on silver fir is overwhelming but from a scientific view, it is largely circumstantial, and a quantitative understanding of how ungulates drive silver fir dynamics is lacking. (3) Browsing herbivores mainly interfere with silver fir development in the sapling stage, but impacts are spatially and temporally variable, and often little related to the size of the herbivore populations. Browsing is only one of a complicated interplay of factors affecting seedling establishment and subsequent growth and survival. Sapling mortality due to browsing has hardly ever been directly measured, let alone been considered in proportion to later mortality caused by inter-tree competition. (4) Most forestry services in central Europe run extensive survey schemes of browsing intensities, but in general, conclusions of 'insufficient regeneration' are unwarranted given the limited predictive value of the data for judging long-term stand dynamics. (5) Ultimately, only a sound understanding of tree population dynamics will help to solve this 'forest-wildlife conflict', but for the time being, it would help if foresters were more open to the idea that silver fir regeneration may be a highly variable and irregular process in both time and space. If silver fir is dependent on rare 'windows of opportunity', wildlife management would also have to abandon the view that strong fluctuations in ungulate populations are to be prevented. (C) 2003 Elsevier Science B.V. All rights reserved.
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Duelli, P., Obrist, M.K., Fluckiger, P.F. (2002) Forest edges are biodiversity hotspots - Also for Neuroptera. Acta Zoologica Academiae Scientiarum Hungaricae. 48:75-87

In a research project investigating the contribution of forest ecotone structures to regional arthropod biodiversity, the neuropteran fauna was assessed at five differently-structured forest edges and, for comparison, 50 m inside the forest. Arthropods were collected from February to November by means of pitfall traps, window (interception) traps and yellow water pans. The traps were installed along transects, reaching horizontally from the open cultivated land into the forest and vertically, oil scaffolds. from the ground LIP to the tree crowns. For each of the species of the insect orders Ncuroptera (59), Raphidioptera (3) and Mecoptera (2), spatio-temporal distribution patterns from open habitats into the forest call be generated from the available database. Only 3 species (5%) were equally or more numerous inside the forest than at the edges. Of particular interest is the distribution in space and time of three sibling species of the Chrysoperla carnea complex (C. lucasina, C. pallida, C. carnea). Neuroptera and Raphidioptera showed their highest species numbers in the shrub belt and the forest mantle, while the Mecoptera preferred the herbaceous fringe. Traps located deepest inside the forest yielded the lowest number of species. In the forest interior, species numbers peaked in the canopy. However, the canopy yielded markedly fewer species than the forest edges. Steep forest edges contained 24% more species than the forest interior, sloped, structurally rich forest edges even 60% more.
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Moretti, M., Conedera, M., Duelli, P., Edwards, P.J. (2002) The effects of wildfire on ground-active spiders in deciduous forests on the Swiss southern slope of the Alps. Journal of Applied Ecology. 39:321-336

1. The influence of fire upon biodiversity has been investigated in many ecosystems under a wide range of environmental conditions. However, there is no information on how fire affects faunal biodiversity in deciduous forest ecosystems prone to winter fires, such as those on the southern slopes of the Alps. 2. The main aim of this study was to analyse the effects of single and repeated fires on the structure and species diversity of spider communities in chestnut forests in southern Switzerland. A second objective was to interpret the ecological response of forest-floor habitats to wildfires, using epigeic spiders as bioindicators. 3. One-hundred and thirty-three spider species were found in pitfall trap samples collected between April and September in burnt and control sites in chestnut coppices. Species richness and community composition were influenced by fire frequency and the time elapsed since the last fire. About 19% of the species were trapped exclusively in sites that had been repeatedly burnt, while 11% occurred only in unburnt coppice. Post-fire development of the spider community was chiefly from individuals that survived in situ. We found no characteristic pioneer species in any of the burnt sites. There were indirect effects of fire on the spider community, through interactions between species arising from the changing environmental conditions following a fire. 4. After a single fire, changes in community composition were only observable during the first 2 years. At sites that had experienced repeated fires, there was a more persistent influence on community composition. These sites were characterized by an increase in species richness and species diversity. The presence of a wide ecological range of species in 'repeated fire' sites was probably due to the mosaic structure of the environment and the wide range of microclimate conditions at the soil surface, with a predominance of xeric conditions. 5. The spider communities of chestnut forests were resilient to disturbance by fire. Both the formerly intensive management of these forests (until the 1950s) and a history of frequent fires that goes back to the Neolithic period have played an important part in the development of the spider community in these forests.
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Suter, W., Graf, R.F., Hess, R. (2002) Capercaillie (Tetrao urogallus) and avian biodiversity: Testing the umbrella-species concept. Conservation Biology. 16:778-788

Because of limited resources, biodiversity conservation practice is often reduced to measures directed at single species in the hope that this will simultaneously benefit other species in the same community. Such "umbrella species" should therefore have habitat requirements that are similar to those of the other species, whereas their spatial needs should be more extensive. The umbrella-species concept is often applied in management yet rarely tested beforehand. The Capercaillie ( Tetrao urogallus ) is a large forest grouse that is declining over much of its range in Central Europe. It is considered a good example of an umbrella species and is now widely receiving attention from forestry managers. We tested its usefulness as an umbrella species in the Swiss Prealps by analyzing relationships between Capercaillie occurrence and avian biodiversity and asked whether both were associated with the same habitat-structure parameters. Study plots with Capercaillie did not hold significantly higher bird diversity than plots without the grouse. However, the species richness and abundance of birds that are more or less restricted to subalpine forests (mountain birds) and that at the same time are on the red list was considerably higher in Capercaillie plots than in those without Capercaillie. Both Capercaillie and mountain birds responded positively to forest structure characterized by intermediate openness, multistoried tree layer, presence of ecotonal conditions, and abundant cover of ericaceous shrubs. Capercaillie may therefore be a useful umbrella species, at least for that part of avian biodiversity of conservation interest.
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Gugerli, F., Senn, J., Anzidei, M., Madaghiele, A., Buchler, U., Sperisen, C., Vendramin, G.G. (2001) Chloroplast microsatellites and mitochondrial nad1 intron 2 sequences indicate congruent phylogenetic relationships among Swiss stone pine (Pinus cembra), Siberian stone pine (Pinus sibirica), and Siberian dwarf pine (Pinus pumila). Molecular Ecology. 10:1489-1497

We studied the phylogenetic relationships among the three stone pine species, Pinus cembra, P. sibirica, and P. pumila, using chloroplast microsatellites and mitochondrial nad1 intron 2 sequences. The three chloroplast microsatellite loci combined into a total of 18 haplotypes. Fourteen haplotypes were detected in 15 populations of P. cembra and one population of P. sibirica, five of which were shared between the two species, and the two populations of P. pumila comprised four species- specific haplotypes. Mitochondrial intron sequences confirmed this grouping of species. Sequences of P. cembra and P. sibirica were identical, but P. pumila differed by several nucleotide substitutions and insertions/deletions. A repeat region found in the former two species showed no intraspecific variation. These results indicate a relatively recent evolutionary separation of P. cembra and P.sibirica, despite their currently disjunct distributions. The species-specific chloroplast and mitochondrial markers of P. sibirica and P. pumila should help to trace the hybridization in their overlapping distribution area and to identify fossil remains with respect to the still unresolved postglacial re- colonization history of these two species.
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Gugerli, F., Sperisen, C., Buchler, U., Magni, F., Geburek, T., Jeandroz, S., Senn, J. (2001) Haplotype variation in a mitochondrial tandem repeat of Norway spruce (Picea abies) populations suggests a serious founder effect during postglacial re-colonization of the western Alps. Molecular Ecology. 10:1255-1263

Populations from 13 elevational transects of Norway spruce [Picea abies (L.) Karst] across the Alpine range were sampled to elucidate the geographical pattern of genetic variation in relation to postglacial re-colonization and to study elevational effects on haplotypic diversity. We assessed fragment length variation in a tandem repeat region of the mitochondrial (mt) nad1 intron 2. This maternally inherited genetic marker is suited to infer migration as it is dispersed by seed only. A total of 10 haplotypes was found, most of which were due to repeat copy number variation. An analysis of molecular variance (AMOVA) showed that overall population differentiation was high (F-ST = 0.41), and it revealed a significant differentiation between monomorphic western and moderately to highly variable eastern Alpine populations. This phylogeographic pattern may be explained by a founder effect during postglacial. re-colonization. An early arriving haplotype, assumed to originate from a western Carpathian refugium, could expand into suitable habitats, reducing the chances for establishment of subsequently arriving haplotypes. On the other hand, the high variation in populations within an Italian transect of the south-eastern Alps may be the consequence of merging migration pathways from and close distance to putative glacial refugia, most likely those assumed in the Carpathian mountains and on the Balkan peninsula or possibly in the central plains of Italy. An effect of elevation on haplotypic diversity was not evident, though a low, but significant, partition of total genetic variation was attributed to among-population variation in one Italian transect. Various factors, such as vertical seed dispersal and forest management, may account for blurring an otherwise established pattern of genetic variation on a small geographical scale.
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Peter, M., Ayer, F., Egli, S. (2001) Nitrogen addition in a Norway spruce stand altered macromycete sporocarp production and below-ground ectomycorrhizal species composition. New Phytologist. 149:311-325

Changes in above- and below-ground ectomycorrhizal species composition are reported following nitrogen addition for 2 yr to a subalpine spruce (Picea abies) stand. The macrofungal sporocarp production was recorded before and during N addition. Belowground ectomycorrhizal diversity was measured by PCR-RFLP analysis of the internal transcribed spacer (ITS) region of rDNA extracted from single mycorrhizal root tips before, and after 1 and 2 yr of fertilization. Sporocarp surveys showed that diversity of the ectomycorrhizal community was drastically reduced following 1 yr of N addition, whereas the saprobic fungal community was not affected. The impact on belowground ectomycorrhizal diversity was less pronounced with no change either in the number of ectomycorrhizal taxa or in Simpson's index of diversity. However, a change in belowground species composition 2 years after N addition was observed with significant changes in abundances of single species. Species which produced large sporocarps accounted for 25% of all sampled root tips. At least 44% of all ectomycorrhizas were formed by species belonging to the Thelephoraceae and Corticiaceae, taxa which produce inconspicuous sporocarps. Addition of N caused a shift in ectomycorrhizal abundance from species forming large sporocarps to species with no or resupinate sporocarps.
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Peter, M., Ayer, F., Egli, S., Honegger, R. (2001) Above- and below-ground community structure of ectomycorrhizal fungi in three Norway spruce (Picea abies) stands in Switzerland. Canadian Journal of Botany-Revue Canadienne De Botanique. 79:1134-1151

The structure of ectomycorrhizal communities was assessed above- and below-ground at three different sites in Switzerland that are dominated by Norway spruce (Picea abies (L.) Karst.). We applied three different approaches to record the ectomycorrhizal species compositions and their spatial structures and compared them among each other. Sporocarp inventories were carried out weekly for 3 years. Belowground, molecular, and morphological analyses of ectomycorrhizal roots were performed. In the 3 years of sporocarp survey, a total of 128 ectomycorrhizal species was observed. Most abundant in number of species were the genera Cortinarius and Russula in all three sites. Using polymerase chain reaction, only 22% of the ectomycorrhizal species observed in sporocarp surveys were detected in mycorrhizas. Species that produce no or inconspicuous sporocarps were most abundant on the root system in all three study sites. The resolution was clearly inferior in morphotype compared with molecular analyses. Spatial analyses of the ectomycorrhizal species composition among subplots revealed high variability within sites. Within sites, spatial structure with positive autocorrelation was observed based on sporocarp data as well as molecular analyses of root tips at the site where the number of analysed mycorrhizas was sufficiently high. No spatial structure could be detected on this scale by morphotype analyses because of the high variability among soil cores. All three methods showed the same site to be separated from the other two based on ectomycorrhizal species compositions. Stand ages and their histories are discussed as possible explanations for these findings.
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Peter, M., Buchler, U., Ayer, F., Egli, S. (2001) Ectomycorrhizas and molecular phylogeny of the hypogeous russuloid fungus Arcangeliella borziana. Mycological Research. 105:1231-1238

Sporocarps of Arcangeliella borziana, a hypogeous russuloid fungus, were found in a subalpine spruce forest in the Swiss Alps. We identified the ectomycorrhizas formed by this species using the ITS-FCR-RFLP method and described them in terms of morphological, anatomical, and molecular features. Phylogenetic placement of A. borziana was studied by comparing nucleotide sequences of the mitochondrial large subunit rRNA gene and the ITS region of nuclear rRNA, respectively, with existing sequence databases, and by comparing the ITS-RFLP pattern with a reference library of approx. 180 mainly basidiomycetous fungi. Sequence analysis of the mitochondrial large subunit rRNA gene confirmed the affiliation of A. borziana to the Russulaceae. Sequence as well as RFLP pattern comparison of the ITS region revealed a close affinity of this species to Lactarius sect. Russularia. This is in accordance with morphological and anatomical studies of the ectomycorrhizas, which share many features with ectomycorrhizas of Lactarius sect. Russularia.
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Straatsma, G., Ayer, F., Egli, S. (2001) Species richness, abundance, and phenology of fungal fruit bodies over 21 years in a Swiss forest plot. Mycological Research. 105:515-523

Fungal fruit bodies were surveyed on a plot area of 1500 m(2) from 1975-99 (excluding 1980-83) in the fungal reserve La Chaneaz in western Switzerland. Fruit bodies were identified and counted on a weekly basis. Species richness and abundances varied strongly between years. More than 400 species were encountered. Many species were transient; particularly rich years showed species occurring for only one year. This indicates that the number of species will substantially increase if the survey is continued. Within years, the species richness, abundances and periods of fruiting were tightly correlated. The abundance data of species within a year seemed symmetrically distributed over their fruiting period. The relation between species richness and abundances within years was studied by fitting species-abundance plots, known from numerical ecology. The surface area under the curves was taken as a parameter for ecological/fungal diversity. Productivity was correlated with the precipitation from lune until October. The time of fruit body appearance was correlated with the temperatures in July and August. As groups, mycorrhizal and saprotrophic species behaved similarly over the years. The productivity of species was compared with their distribution in The Netherlands indicating a correlation between the level of local abundance and the geographic range of species.
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Parsons, S., Boonman, A.M., Obrist, M.K. (2000) Advantages and disadvantages of techniques for transforming and analyzing chiropteran echolocation calls. Journal of Mammalogy. 81:927-938

Bat researchers currently use a variety of techniques that transform echolocation calls into audible frequencies and allow the spectral content of a signal to be viewed and analyzed. All techniques have limitations and an understanding of how each works and the effect on the signal being analyzed are vital for correct interpretation. The 3 most commonly used techniques for transforming frequencies of a call are heterodyne, frequency division, and time expansion, Three techniques for viewing spectral content of a signal are zero-crossing, Fourier analysis, and instantaneous frequency analysis. It is important for bat researchers to be familiar with the advantages and disadvantages of each technique.
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Brunner, I., Rigling, D., Egli, S., Blaser, P. (1999) Response of Norway spruce seedlings in relation to chemical properties of forest soils. Forest Ecology and Management. 116:71-81

The response of Norway spruce seedlings to 157 samples of upper soil layers obtained from 66 forest sites with Norway spruce distributed throughout Switzerland was examined during a 4 months growth chamber study. The pH values of the soil samples ranged from 2.95 to 7.41, with 43% of the samples being acidic (pH<4.75) and with high concentrations of exchangeable Al. A comparison of two soil extraction methods, the NH4Cl-extraction representing the 'exchangeable' fraction of cations in soils and the NH4-acetate-EDTA-extraction representing the 'extractable' (potentially plant available) fraction, revealed similar results only for the cation K. With the NH4-acetate- EDTA-extraction, slightly more Al was extracted in nearly all the samples, and distinctly more Ca was extracted from samples with pH>6. Seedlings growing in these soil samples showed clear differences in biomass responses, when soils were arranged in classes according to the pH, the sum of 'exchangeable' basic cations (BC), or the BC/Al molar ratio. Reduced biomass was observed at pH<4.75, at BC<100 mmol, kg(-1), and at a BC/Al ratio <1. Additionally, a significant positive relationship occurred between root biomass and BC/Al ratio in soils with a low BC/Al ratio (<10), indicating a potential for the use of the BC/Al ratio of soil extracts to assess the risk of Al stress. In acidic soils, Ca concentrations in the shouts were reduced but Al concentrations were enhanced. This trend was also apparent when soils were arranged according the BC/Al ratio. Here, Ca concentrations in the shoots were steadily enhanced from BC/Al <1 to >1000, whereas Al was reduced. The Ca concentrations in the shouts were similar to the 'exchangeable' amount of Ca in the soils, whereas for K and Mg an accumulation in the shoots occurred. The Al concentrations in the shoots, on the other hand, indicated a constant translocating rate of Al from the roots to the shoots independent of the 'exchangeable' amounts of Al in the soils. (C) 1999 Elsevier Science B.V. All rights reserved.
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Duelli, P., Obrist, M.K., Schmatz, D.R. (1999) Biodiversity evaluation in agricultural landscapes: above- ground insects. AGRICULTURE ECOSYSTEMS & ENVIRONMENT. 74:33-64

In agriculture, sustainability can be linked to ecological resilience. In view of present or imminent environmental changes in agricultural landscapes, the diversity of species and genotypes, particularly of potential beneficials and alternative prey, may become of increasing importance. However, the available methods and empirical data concerning species diversity of above-ground insects in agricultural landscapes do not yet allow comprehensive evaluation. Standardized inventory methods must be used more rigorously and over longer time periods to detect significant differences in space and in time. Indicator groups for biodiversity estimates must be defined. Methods for optimizing the reliability and comparability of faunistic inventories are proposed, including rarefaction for reference functions and estimation of species numbers per unit area. Recommendations for optimum sampling periods and average empirical numbers for species diversity and abundance of major arthropod groups are given and compared to published data. In general, organismal biodiversity is higher in less intensely cultivated habitats. Apart from the impact of biocides, variation in species diversity often depends on the biodiversity of the surroundings (mosaic landscape) rather than on differing management regimes. The focus in preserving or enhancing, but also in evaluating biodiversity in cultivated areas thus should clearly be on the landscape level. Structural biodiversity in agricultural areas appears to be correlated with functional and organismal biodiversity of the above-ground insect fauna. (C)1999 Elsevier Science B.V. All rights reserved.
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Henry, C.S., Brooks, S.J., Johnson, J.B., Duelli, P. (1999) Revised concept of Chrysoperla mediterranea (Holzel), a green lacewing associated with conifers: courtship songs across 2800 kilometres of Europe (Neuroptera : Chrysopidae). Systematic Entomology. 24:335-350

The Holarctic carnea-group of Chrysoperla green lacewings consists of numerous cryptic, sibling species, distinguished principally by vibrational courtship songs. A European member of this species-group, C. mediterranea (Holzel), was originally diagnosed by its dark green coloration, red band across the front of the head, narrow wings, minute basal dilation of the pretarsus and ecological association with pines. Here we describe its courtship and mating song, which uniquely distinguishes the species from all other members of the carnea- group in Europe. Males and females both produce a single type of song, characterized by a long train of short, closely spaced volleys and nearly constant carrier frequency. Measured song features are nearly invariant across a large geographical range that extends well outside that previously known for C. mediterranea. Principal components analysis confirms the uniqueness of the mediterranea song in comparison with five other sympatric song species of the carnea-group. Populations which show the mediterranea song phenotype do not necessarily retain all of the traditional morphological features of the species, particularly in eastern parts of the range. Specifically, the green coloration may be less intense, the wings broader and the pretarsal basal dilation larger, resulting in significant morphological overlap with other song species. Larval morphology and ecophysiology also fail to distinguish C. mediterranea from other song species. Based on unique song phenotype, however, we conclude that C. mediterranea is a valid biological species, which can also be recognized in museum collections when a suite of physical attributes is used.
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Senn, J. (1999) Tree mortality caused by Gremmeniella abietina in a subalpine afforestation in the central Alps and its relationship with duration of snow cover. European Journal of Forest Pathology. 29:65-74

Tree survival and causes of mortality were studied in an experimental afforestation in the upper subalpine forest zone in the Swiss Alps. A total of 59.8% of Pinus cembra and 45.6% of Pinus mugo were killed by Gremmeniella abietina during the first 20 years after planting, compared to 1.5% of Larix decidua trees. The mortality rates caused by G. abietina were highly correlated with the duration of snow cover in spring. Tree losses were lowest at sites where the snow melted early and highest at sires where the snow ablation was delayed in spring. Tree mortality varied greatly between years. In the year after the coldest summer of the observation period mortality due to G. abietina infections was highest, suggesting high susceptibility of trees in poor condition, Phacidium infestans, which was the second most important factor for mortality in P. cembra, killed trees irrespective of their condition. Other biotic and abiotic causes of tree mortality had negligible influence compared with the impact of G. abietina and P. infestans. Excluding anthropogenic impacts, the diverse spatial pattern of forested and treeless sites close to the subalpine timberline may predominantly result from the action of parasitic fungi, depending on the ablation pattern of the snow cover in spring.
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Duelli, P., Obrist, M.K. (1998) In search of the best correlates for local organismal biodiversity in cultivated areas. Biodiversity and Conservation. 7:297-309

Based on a transect consisting of 19 identical trap stations in cultivated areas and seminatural habitats, the correlation of species numbers of higher taxonomic groups with total species numbers of flowering plants and arthropods per trap site was calculated. A total of 191 214 invertebrate specimens and 2221 species of plants and animals were analysed. Considering the value of the correlation coefficient R-2 as well as the effort for sorting and identification, a `top twenty' list of indicator groups favours Heteroptera, flowering plants, Symphyta and aculeate Hymenoptera as the best choice for biodiversity evaluation. In general, flight traps rated better than pitfall traps. In most taxonomic groups, diversity indices such as the Shannon and the Simpson index were only weakly correlated with local species diversity.
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Nicolotti, G., Egli, S. (1998) Soil contamination by crude oil: impact on the mycorrhizosphere acid on the revegetation potential of forest trees. Environmental Pollution. 99:37-43

In vitro and greenhouse biotests were carried out to study the effects of various concentrations of crude oil on the mycorrhizosphere and the ability of ectomycorrhizal fungi to colonise Norway spruce and poplar seedlings grown on contaminated soil. Ectomycorrhizal fungi grown in pure cultures showed a variety of reactions to crude oil, ranging from growth stimulation to total inhibition of growth, depending on the species of fungi. Germination of poplar and spruce seeds was not significantly affected. The growth of spruce seedlings was not affected by crude oil, whereas that of poplar seedlings was significantly reduced at high concentrations. None of the concentrations had any effect on the degree of ectomycorrhizal and endomycorrhizal colonisation of poplar. With spruce, however, the ectomycorrhizal fungi showed species-specific reactions to increasing concentrations, in accordance with the results of the pure culture test. The length of time between soil contamination and seeding affects both seedling growth and the mycorrhizal infection potential of the soil. The results confirm the importance of mycorrhizal fungi in the bioremediation of soils contaminated by crude oil. (C) 1998 Elsevier Science Ltd. All rights reserved.
times cited: 6

Obrist, M.K., Wenstrup, J.J. (1998) Hearing and hunting in red bats (Lasiurus borealis, Vespertilionidae): Audiogram and ear properties. Journal of Experimental Biology. 201:143-154

We examined aspects of hearing in the red bat (Lasiurus borealis) related to its use of biosonar. Evoked potential audiograms, obtained from volume-conducted auditory brainstem responses, were obtained in two bats, and the sound pressure transformation of the pinna was measured in three specimens, Field-recorded echolocation signals were analysed for comparison, The fundamental sonar search calls sweep from 45 to 30 kHz (peak energy at 35 kHz), approach-phase calls sweep from 65 to 35 kHz (peak 40 kHz) and terminal calls sweep from 70 to 30 kHz (peak 45 kHz). The most sensitive region of the audiogram extended from 10 kHz to 45-55 kHz, with maximum sensitivity as low as 20 dB SPL occurring between 25 and 30 kHz, A relative threshold minimum occurred between 30 and 50 kHz. With increasing frequency, the acoustic axis of the pinna moves upwards and medially, The sound pressure transformation was noteworthy near 40-45 kHz; the acoustic axis was closest to the midline, the -3 dB acceptance angles showed local minima, and the pinna gain and interaural intensity difference were maximal, These results are related to the known echolocation and foraging behavior of this species and match the spectral components of approach-and final-phase calls, We conclude that coevolution with hearing prey has put a higher selective pressure on optimizing localization and tracking of prey than on improving detection performance.
times cited: 1

Suter, W. (1998) Conservation biology and biodiversity strategies - Introduction - Involving conservation biology in biodiversity strategy and action planning. Biological Conservation. 83:235-237

times cited: 2

Suter, W. (1998) The effect of predation by wintering cormorants Phalacrocorax carbo on grayling Thymallus thymallus and trout (Salmonidae) populations: two case studies from Swiss rivers. Reply. Journal of Applied Ecology. 35:611-616

Data relating to possible predatory effects of cormorants Phalacrocorax carbo (L.) on grayling Thymallus thymallus (L.) in the river Rhine did not support hypotheses of overfishing, but were consistent with changes in the fish population resulting from variable recruitment and density-dependent effects (Suter 1995). In a government report, fisheries managers using the same data claimed to have found a causal relationship between cormorant predation and grayling decline (Staub et nl. 1992). In their comment, these authors argue that certain data transformations and statistical procedures in my paper were responsible for the different outcome (Staub cf al. 1998). However, the authors are unable to quantify any effects of procedures they question, and resort to vague reasoning. Their technical objections are either irrelevant or misleading, since they repeatedly make wrong assumptions or misinterpret Darts of my analysis. Different interpretations of predation effects are rather a consequence of the shortcomings of the original report: Staub et al. (1992) had not applied any statistical treatment to the data nor tested any hypotheses, but had arrived at their 'conclusions' simply by looking at a number of raw graphs depicting grayling catches grouped by fish-length classes. Moreover, their approach (both in the original report and in the present comment) suffers from a lack of biological understanding, particularly of dynamic processes in fish populations and density-related effects.
times cited: 2

Duelli, P. (1997) Biodiversity evaluation in agricultural landscapes: An approach at two different scales. AGRICULTURE ECOSYSTEMS & ENVIRONMENT. 62:81-91

Evaluating biodiversity in agricultural areas requires two steps: (i) adequate measurement and (ii) pertinent interpretation. Since the whole spectrum of biodiversity in the sense of the Rio Convention cannot possibly be measured as such, adequate measurable correlates or surrogates have to be found. One possibility are standardized inventories to assess species diversity in specious groups of arthropods. They can provide reproducible and comparable values for estimates of site-specific biodiversity in the form of averaged rarefaction functions for the relationship between numbers of individuals and numbers of species in different habitats. Examples of 'rapid biodiversity assessment' are presented and their possibilities and limitations are discussed. At a higher integrative level, biodiversity evaluation can be based on landscape parameters. According to a proposed conceptual model, the 'mosaic concept', regional biodiversity mainly depends on structural parameters such as habitat diversity and landscape heterogeneity, and functionally on metacommunity dynamics. Approaches with a combination of both site-specific biodiversity measures and assessments of habitat diversity and heterogeneity are not yet established, but in the near future may lead to a scientifically based evaluation of the potential for increasing biodiversity by appropriate landscape management. In the light of scenarios for global change, maintaining high levels of overall biodiversity in agroecosystems may become as important for ecological sustainabilty as keeping up high abundances of presently well- adapted beneficial organisms. (C) 1997 Elsevier Science B.V.
times cited: 29

Duelli, P., Zahradnik, P., Knizek, M., Kalinova, B. (1997) Migration in spruce bark beetles (Ips typographus L) and the efficiency of pheromone traps. Journal of Applied Entomology-Zeitschrift Fur Angewandte Entomologie. 121:297-303

Mark-release-recapture experiments with both newly emerged and flight experienced Ips typographus L. were performed in a pine forest near Prague. Three concentric trap circles around the release site with a radius of 5 m, 200 m and 500 m, and intertrap distances of 6 m, 16 m and, maximally, 40 m, were installed with the intention of collecting all dispersing bark beetles ready to respond to pheromone lures. The results show that even without wind and no potential host trees in the surroundings, only about one-third (35.4%) of the emerging beetles in an infested site can be eliminated locally with phermomone traps. At least 12.2% of the emerging beetles (25.7% of the recaptures), perform an adaptive migration flight, which brings them beyond the range of local pheromone traps. The estimated proportion of emigrants can rise over 50%, if most of the freshly emerged beetles that have never been recaptured are assumed to have left the experimental area. Electroantennograms recorded in the laboratory at different times after emergence indicate that the delayed response to aggregation pheromones in migrating bark beetles is not the result of a delayed maturation of the antennal receptor cells, but obviously governed by the central nervous system. The notion of precopulatory migration in 25-50% of the individuals in an I. typographus population can explain why pheromone traps can never eliminate all emerging beetles, and why so many bark beetles can be collected far away from any breeding sites.
times cited: 8

Suter, W. (1997) Roach rules: Shoaling fish are a constant factor in the diet of cormorants Phalacrocorax carbo in Switzerland. Ardea. 85:9-27

The spatial and temporal Variation in the diet of Cormorants Phalacrocorax carbo visiting Switzerland in the non-breeding season was studied from 1985-1992, by means of regurgitated pellets and stomach contents. The results, combined with the data of most other dietary studies from Switzerland since 1974, rest on 4810 samples representing 24 122 fish from ten lakes and nine river stretches. Of 31 fish species occurring at the feeding sites, 23 were found in the diet, yet 5-7 accounted for 85-95% by numbers. Roach Rutilus rutilus was found in 58% of all samples and, together with Perch Perca fluviatilis, accounted for 65% by numbers. Diet was habitat-specific, and three main types could be discerned by canonical variate analysis: (1) diet strongly dominated by Roach and Perch, typical for most eutrophic lakes and empounded rivers; (2) diet containing a high percentage of whitefish Coregonus sp. and Tench Tinca tinca, on two lakes with extremely low Roach biomass; (3) diet dominated by Grayling Thymallus thymallus, Trout Salmo trutta or riverine cyprinids, in free-running rivers. Seasonal Variation was found to be small in Roach- dominated diets but strong at some other sites. Prey size ranged from small fry to adult fish of up to 800 g and was on average larger in rivers than in lakes. Small fish (< 12 cm) were mainly taken in lakes and reservoirs. At a landscape scale, the high proportion of Roach in the diet was associated with a preference for eutrophic lakes that support high densities of Roach and Perch. Roach was estimated to provide > 50% of the biomass ingested by Cormorants in Swiss waters. At a local scale, possible preferences were less conclusive, but Roach was apparently still overrepresented compared to abundance while whitefish was underrepresented. Roach and Perch are both shoaling species and are hunted by Cormorants which themselves congregate in large flocks. A similar preference for highly gregarious fish is apparent in most other studies from continental European inland sites.
times cited: 6

Henry, C.S., Brooks, S.J., Johnson, J.B., Duelli, P. (1996) Chrysoperia lucasina (Lacroix): A distinct species of green lacewing, confirmed by acoustical analysis (Neuroptera: Chrysopidae). Systematic Entomology. 21:205-218

The existence of cryptic, sibling species, distinguished principally by vibrational courtship songs, has been confirmed for the carnea-group of Chrysoperla green lacewings in Europe and western Asia. One member of this species-group, C.lucasina (Lacroix), is characterized by several morphological traits as well, but its taxonomic validity has been considered uncertain due to the subtle and variable nature of those traits. Here, we describe the calling and courtship songs of C.lucasina, which uniquely distinguish that taxon from all other members of the carnea-group in Europe. The male of C.lucasina produces two slightly but consistently different types of songs, one while calling and the other while dueting with a female. The female produces just one type of song, identical to the male's calling song, which is used for both calling and dueting. Measured features of the songs of C.lucasina are nearly invariant over a broad geographical area, from the Canary Islands to Cyprus and from northern Africa to the U.K. Similarly, at least one morphological feature, the presence of a dark stripe on the pleuron of the second abdominal segment, characterizes all adult individuals identified acoustically as C.lucasina. Furthermore, larval head markings vary little among different populations of the song species. We conclude that C. lucasina is a valid biological species, which can also be recognized in museum collections by a suite of morphological attributes. We also briefly compare the songs and adult morphology of C.lucasina with five other currently unnamed song Species of the carnea-group whose geographic ranges overlap extensively with it.
times cited: 9

Suter, W., Morel, P. (1996) Pellet analysis in the assessment of Great Cormorant Phalacrocorax carbo diet: Reducing biases from otolith wear when reconstructing fish length. Colonial Waterbirds. 19:280-284

Fish otoliths recovered from pellets of piscivorous birds are often used to reconstruct size and mass of the ingested fish, but erosion of otoliths by gastric fluids usually results in underestimations. We tested the hypothesis that using only uneroded otoliths would greatly improve fish length estimations. In so doing, we compared size-frequency distributions of grayling (Thymallus thymallus) reconstructed from uneroded and eroded otoliths in pellets of Great Cormorants (Phalacrocorax carbo) with size-frequency distributions from a small sample of stomach contents and with samples from various types of fisheries, all from the Rhine River in Switzerland and Germany. Distributions reconstructed from eroded and uneroded otoliths were significantly different. Distributions from worn otoliths failed to delineate different cohorts and produced strong underestimates of fish lengths, thus not identifying larger grayling at all. Distributions reconstructed from otoliths classified as ''uneroded'' represented th whole range of sih sizes eaten and showed the different grayling cohorts, similar to the catch samples, Compared to these, however, average length-at-age in cohort 2 was slightly underestimated (ca. 6-9% in 32 cm long grayling). It is concluded that, at least in fish with relatively large and robust otoliths, careful exclusion of otoliths showing signs of erosion can remove much of the bias in indiscriminately reconstructed size-frequency distributions, thus greatly improving conclusions about the age or size composition of fish in the cormorant diet.
times cited: 7

Fenton, M.B., Audet, D., Obrist, M.K., Rydell, J. (1995) Signal Strength, Timing, and Self-Deafening - the Evolution of Echolocation in Bats. Paleobiology. 21:229-242

We propose that the ancestors of bats were small, nocturnal, sylvatic gliders that used echolocation for general orientation. Their echolocation calls were short, low intensify, broadband clicks, which translated into a very short operational range. In the lineage that gave rise to bats, a switch to stronger, tonal signals permitted the use of echolocation to detect, track, and assess flying insects in subcanopy settings. We propose that these animals hunted from perches and used echolocation to detect, track, and assess flying insects, which they attacked while gliding. In this way, the perfection of echolocation for hunting preceded the appearance of napping night, which marked the emergence of bats. Flapping night had appeared by the Eocene when at least eight families are known from the fossil record. Stronger signals and adaptations to minimize self-deafening were central to the perfection of echolocation for locating flying prey. Echolocation constituted a key innovation that permitted the evolution and radiation of bats. At the same time, however, its short effective range imposed a major constraint on the size of bats. This constraint is associated with flight speed and the very small time intervals from detection of, and contact with a flying target. Gleaning and high duty cycle echolocation are two derived approaches to hunting prey in cluttered situations, places where echoes from background and other objects arrive before or at the same time as echoes from prey. Both had appeared by the Eocene.
times cited: 25

Hanhimaki, S., Senn, J., Haukioja, E. (1995) The Convergence in Growth of Foliage-Chewing Insect Species on Individual Mountain Birch Trees. Journal of Animal Ecology. 64:543-552

1. In two subsequent years and under standardized experimental conditions, we bioassayed the leaf quality of the same 20 subarctic mountain birches Betula pubescens ssp. tortuosa with 14 sawfly and one lepidopteran species to study the effects of annual and seasonal leaf quality variation on herbivore growth, and potential species interactions. The larval periods of the 15 species covered the whole growth season of birch. 2. Insect growth rates were higher in 1987 than in 1988, except for two late-season species. In spite of the large annual variation in foliage quality, the relative ranking of individual trees for growth of the herbivore species remained constant between the 2 years, Differences in insect growth between the years seemed to be explained by plant vigour. 3. Birch leaf quality decreases rapidly within a season. The early species had two to three times higher relative growth rates (RGR) than species feeding in mid- and late season. Growth rates of the early season species also varied more than those of late season, both among insect species and among individual trees. 4. We compared tree- specific herbivore growth between pairs of species to investigate similarity of the trees for herbivores. All significant correlations within a year between the RGR of the herbivore species were positive, but significant correlations were found between early and mid-season species only, i.e. at the time when foliage quality was temporally best and most variable among trees. When split into years, these positive correlations were more common (44% of cases) in 1988, when foliage quality was poor, than in 1987 (1%). 5. Growth of several insect species differed significantly among the 20 trees in 1987 and in the early season of 1988. This happened when larvae were consuming high-quality foliage, and indicated that the herbivore species were able to adjust their growth performance to take advantage of high-quality diets. But they did this in species-specific ways, as indicated by the fewer significant correlations in growth between herbivore species on high-quality than on low-quality diets. Accordingly, growth of different herbivore species converged under conditions of poor leaf quality, and herbivore species showed some specialization when leaf quality was high.
times cited: 19

Senn, J., Haukioja, E. (1994) Reactions of the Mountain Birch to Bud Removal - Effects of Severity and Timing, and Implications for Herbivores. Functional Ecology. 8:494-501

1. Apical buds of mountain birches were clipped to simulate browsing by herbivores, and leaf traits of the subsequent leaf generation were recorded. 2. Clipping of only one quiescent apical bud from tips of all branches in winter induced the whole ramet to produce short shoot leaves which were significantly larger and contained more water compared with leaves of unmanipulated ramets of the same birch individual. Such leaves were previously shown to be more suitable for herbivores than leaves of unmanipulated control trees. 3. Increasing the number of clipped buds to three or four per branch further intensified the responses. This demonstrated the importance of apical meristems for the regulation of resource allocation to growing short shoot leaves. Tree-by-treatment interactions were significant, indicating individual responses of the trees. 4. Removal of expanding apical buds in spring at the time of bud break induced responses that were similar to those in trees clipped in winter. Again individual trees responded differently so that the tree-by-treatment interaction was significant but the main effect of treatment was only marginally significant. Trees with advanced bud expansion did not respond, or responded only weakly, to the clipping treatment, whereas trees with delayed bud development still responded. Late leafing characterizes small-leaved dwarf birch- type trees and there was a significant negative correlation between leaf size in control ramets and increase in leaf size caused by spring clipping of buds. 5. The sensitivity of mountain birch to disturbances of apical dominance might make it possible for herbivores to manipulate the quality of their food resource.
times cited: 14

Egli, S., Amiet, R., Zollinger, M., Schneider, B. (1993) Characterization of Picea-Abies (L) Karst Ectomycorrhizas - Discrepancy between Classification According to Macroscopic Versus Microscopic Features. Trees-Structure and Function. 7:123-129

In a 3-year study of ectomycorrhizal diversity in 2 Norway spruce stands in Switzerland the macroscopically classified ectomycorrhizal types were analyzed microscopically to compare the results of the 2 approaches. A total of 22 ectomycorrhizal types were macroscopically classified in the 2 stands. Microscopic investigations - particularly of mantle structures - resulted in the identification of 7 additional types to give a total of 29. These additional types resulted from separation of macroscopically identical types occurring on both stands (type-pairs) at the microscopic level. The problematic nature of characterization and classification of ectomycorrhizas is discussed.
times cited: 10

Egli, S., Kalin, I. (1991) Root Window Technique for in-Vivo Observation of Ectomycorrhiza on Forest Trees. Methods in Microbiology. 23:423-433

times cited: 1

Duelli, P., Studer, M., Marchand, I., Jakob, S. (1990) Population-Movements of Arthropods between Natural and Cultivated Areas. Biological Conservation. 54:193-207

times cited: 76

Egli, S., Kalin, I. (1990) The Root Window - a Technique for Observing Mycorrhizae on Living Trees. AGRICULTURE ECOSYSTEMS & ENVIRONMENT. 28:107-110

times cited: 3

Duelli, P. (1989) Faunistic Studies on Maize Arthropods - Closing Remarks. Acta Phytopathologica Et Entomologica Hungarica. 24:241-242

times cited: 0

Duelli, P., Studer, M., Marchand, I. (1989) The Influence of the Surroundings on Arthropod Diversity in Maize Fields. Acta Phytopathologica Et Entomologica Hungarica. 24:73-76

times cited: 4

Egli, S., Gfeller, H., Bigler, P., Schlunegger, U.P. (1988) Isolation and Identification of the Sesquiterpene (+/-)- Torreyol from Pure Cultures of the Ectomycorrhizal Fungus Cortinarius-Odorifer Britz. European Journal of Forest Pathology. 18:351-356

times cited: 0

Haefelfinger, D., Duelli, P. (1987) A Sampling Method for Absolute-Population Estimates of Invertebrate Communities. Revue Suisse De Zoologie. 94:515-524

times cited: 1

Huber, M., Duelli, P. (1987) Flight Activity of Coleoptera over Monocultures and Seminatural Areas. Revue Suisse De Zoologie. 94:525-532

times cited: 2

Duelli, P. (1986) A Missing Link in the Evolution of the Egg Pedicel in Lacewings. Experientia. 42:624-624

times cited: 2

Duelli, P., Studer, M., Naf, W. (1986) The Flight of Bark Beetles Outside of Forest Areas. Journal of Applied Entomology-Zeitschrift Fur Angewandte Entomologie. 102:139-148

times cited: 7