Ecology of the ant community on the alpine tree line ecotone

Die Ameisengemeinschaften alpiner Lebensräume sind noch wenig untersucht, auch in Mitteleuropa. Der hochmontane Nadelwald, das Waldgrenz-Ökoton und der alpine Rasen unmittelbar oberhalb der Waldgrenze wurden untersucht. Insgesamt wurden 14 verschiedene Ameisenarten vorgefunden. Ein höherer Artenreichtum wurde an den Standorten direkt am Ökoton vorgefunden, zusammen mit einer höheren Funktionellen Diversität. Im Wald wurde ein größerer Artenpool vorgefunden, doch das gemeinsame Vorkommen von Arten an einem Standort war höher an der Waldgrenze. Die Ameisengemeinschaft veränderte sich über den Gradienten, sodass im Wald die dominante Rote Waldameise vorherrschte und im alpinen Rasen die subdominante Alpine Sklavenameise numerisch überwog. Die Dichte der Roten Waldameise, die Deckung von Sträuchern und der Humus-Gehalt des Bodens beeinflussten signifikant die Präsenz und Abundanz der anderen Ameisenarten. Die Ressourcennutzung und -limitierung wurde experimentell mit Ködern und stabilen Isotopen untersucht und ergab, dass zuckerhaltige Köder stärker besucht wurden und sich die trophische Stellung (und die Ressourcenlimitierung) der Ameisen über das Ökoton veränderte, mit einer niederen Stellung im Walde. Dieser Effekt ist das Ergebnis einer intensiveren Interaktion mit pflanzensaftsaugenden Homopteren (Pflanzenläusen) im Wald, die einen wichtigen Lieferanten von Pflanzen-Kohlenhydraten für die Ameisen darstellen. Im alpinen Rasen, wo diese Interaktion schwächer vertreten war, wurde eine stärker karnivore Ernährung der Ameisen festgestellt. Die Präsenz von Trophobionten beeinflusste – auf dem Weg über die Dichte der Roten Waldameisen – die gesamte Gemeinschaftszusammensetzung der Ameisen und deren Ressourcenlimitierung über den untersuchten Gradienten.Alpine ant communities are poorly studied from an ecological perspective, even in central Europe. The upper montane forest, the tree line ecotone and the alpine environment directly above the tree line were investigated. The alpine grassland belt just above the tree line represents the upper distribution limit of most ant species in Europe. Fourteen different ant species were identified. Elevated species richness was found directly at the ecotone, along with higher functional diversity of the ant community. In the forest a larger potential species pool was detected, but species packing per site was denser at the ecotone. Wood ants dominated in the forest, whereas the subordinate alpine slave-ant (Formica lemani) was numerically dominant in the alpine grassland. Wood ant abundance, shrub cover and soil humus content was found to significantly influence the presence and abundance of all other ant species. The feeding preferences were investigated experimentally using baits and with stable isotope analysis. Sugar baits were used more frequently and a trophic change over the ecotone, with a higher trophic position at the alpine sites and a lower one in the forest was detected. This pattern was probably driven by the higher presence of plant sucking homopterans that provides a consistent source of plant-derived carbohydrates in the forest. In the alpine setting this interaction becomes more scarse and rather carnivore feeding behaviour was detected. This trophobiotic interaction most likely influenced the entire community composition and changed resource limitations across the ecotone

Ant Diversity and Community Composition in Alpine Tree Line Ecotones

Ants are crucial for the functioning of many terrestrial ecosystems, but detailed knowledge of their ecological role is often lacking. This is true for high mountains where a steep environmental gradient exists from mountainous forest, densely populated by ants, to grassland habitats above the tree line, harboring a sparse ant community. We assessed ant communities in and around the tree line ecotone on five slopes in the southern-central Alps, focusing on their species diversity, community composition, and functional dimensions. Species richness and functional diversity were highest directly at the ecotone. Ant community composition was shaped by elevation and shrub cover. Further, the abundance of the dominant mound-building red wood ants (Formica s. str.) influenced the community composition of the subordinate species. We conclude that over the tree line ecotone a shift in predominance from biotic limitations in the forest to abiotic filters in the alpine environment takes place

Ant Diversity and Community Composition in Alpine Tree Line Ecotones

Ants are crucial for the functioning of many terrestrial ecosystems, but detailed knowledge of their ecological role is often lacking. This is true for high mountains where a steep environmental gradient exists from mountainous forest, densely populated by ants, to grassland habitats above the tree line, harboring a sparse ant community. We assessed ant communities in and around the tree line ecotone on five slopes in the southern-central Alps, focusing on their species diversity, community composition, and functional dimensions. Species richness and functional diversity were highest directly at the ecotone. Ant community composition was shaped by elevation and shrub cover. Further, the abundance of the dominant mound-building red wood ants (Formica s. str.) influenced the community composition of the subordinate species. We conclude that over the tree line ecotone a shift in predominance from biotic limitations in the forest to abiotic filters in the alpine environment takes place

The trinity of ecological contrasts: a case study on rich insect assemblages by means of species, functional and phylogenetic diversity measures

Abstract Background The ‘classical’ concept of species diversity was extended in the last decades into other dimensions focusing on the functional and phylogenetic diversity of communities. These measures are often argued to allow a deeper understanding of the mechanisms shaping community assembly along environmental gradients. Because of practical impediments, thus far only very few studies evaluated the performance of these diversity measures on large empirical data sets. Here, data on species-rich riparian moth communities under different flood regimes and from three different rivers has been used to compare the power of various diversity measures to uncover ecological contrasts. Results Contrary to the expectation, classical metrics of species diversity (Hill numbers N1, N2 and Ninf) and evenness (Buzas-Gibson’s E and Pielous’s J) turned out to be the most powerful measures in unravelling the two gradients investigated in this study (e.g. flood regime and region). Several measures of functional and phylogenetic diversity tended to depict either only one or none of these contrasts. Rao’s Q behaved similarly as species diversity and evenness. NTI and NRI showed a similar pattern among each other but, were different to all the other measures. Functional Divergence also behaved idiosyncratically across the 28 moth communities. The community weighted means of nearly all individual functional traits showed significant ecological patterns, supporting the relevance of the selected traits in shaping assemblage compositions. Conclusions Species diversity and evenness measures turned out to be the most powerful metrics and clearly reflected both investigated environmental contrasts. This poses the question when it is useful to compile the additional data necessary for the calculation of additional diversity measures, since assembling trait bases and community phylogenies often requires a high work load. Apart from these methodological issues, most of the diversity measures related to communities of terrestrial insects like moths increased in forests that still are subject to flooding dynamics. This emphasizes the high conservation value of riparian forests and the importance of keeping and restoring river dynamics as a means of fostering also terrestrial biodiversity in floodplain areas

Permeability of habitat edges for Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman 1816) in an alpine landscape

We tracked the movements of adult Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman, 1816) in high-elevation (> 1800 meters a.s.l.) grasslands in the Austrian Alps in order to test if an anthropogenic boundary (= an asphalt road) had a stronger effect on butterfly movement than natural habitat boundaries (trees, scree, or dwarf shrubs surrounding grassland sites). 373 individuals (136 females, 237 males) belonging to 11 Erebia species were observed in one flight season (July–August 2013) while approaching or crossing habitat edges. Erebia pandrose (Borkhausen, 1788) was the most abundant species with 239 observations. All species studied were reluctant to cross habitat boundaries, but permeability was further strongly affected by the border type. Additional variables influencing movement probability were species identity and the time of the day. In E. pandrose, for which we had sufficient observations to analyse this, individuals were more likely to cross a boundary in the morning and in the late afternoon than at midday. Erebia euryale (Esper, 1805) and E. nivalis Lorković & de Lesse, 1954 were more likely to leave a habitat patch than their studied congeners. The key result of our study is that the paved road had the lowest permeability among all edge types (0.1 likelihood of crossing when approaching the edge). A road cutting across a conservation area (viz. a national park) thus hinders inter-patch exchange among Ringlet butterflies in the alpine zone, even though theoretically they ought to be able to fly across

Permeability of habitat edges for Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman 1816) in an alpine landscape

We tracked the movements of adult Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman, 1816) in high-elevation (> 1800 meters a.s.l.) grasslands in the Austrian Alps in order to test if an anthropogenic boundary (= an asphalt road) had a stronger effect on butterfly movement than natural habitat boundaries (trees, scree, or dwarf shrubs surrounding grassland sites). 373 individuals (136 females, 237 males) belonging to 11 Erebia species were observed in one flight season (July–August 2013) while approaching or crossing habitat edges. Erebia pandrose (Borkhausen, 1788) was the most abundant species with 239 observations. All species studied were reluctant to cross habitat boundaries, but permeability was further strongly affected by the border type. Additional variables influencing movement probability were species identity and the time of the day. In E. pandrose, for which we had sufficient observations to analyse this, individuals were more likely to cross a boundary in the morning and in the late afternoon than at midday. Erebia euryale (Esper, 1805) and E. nivalis Lorković & de Lesse, 1954 were more likely to leave a habitat patch than their studied congeners. The key result of our study is that the paved road had the lowest permeability among all edge types (0.1 likelihood of crossing when approaching the edge). A road cutting across a conservation area (viz. a national park) thus hinders inter-patch exchange among Ringlet butterflies in the alpine zone, even though theoretically they ought to be able to fly across

Management Intensification of Hay Meadows and Fruit Orchards Alters Soil Macro- Invertebrate Communities Differently

Land-use changes and especially management intensification currently pose a major threat to biodiversity both on and beneath the soil surface. With a comparative approach, we investigated how management intensity in orchards and meadows influences soil macro-invertebrate communities in a North-Italian Alpine region. We compared soil fauna assemblies from traditional low-input sites with respective intensively managed ones. As expected, the taxonomical richness and diversity were lower in both intensive management types. Extensive management of both types revealed similar communities, while intensification led to substantial differences between management types. From these results, we conclude that intensification of agricultural practices severely alters the soil fauna community and biodiversity in general, however, the direction of these changes is governed by the management type. In our view, extensive management, traditional for mountain areas, favors soil fauna communities that have adapted over a long time and can thus be viewed as a sustainable reference condition for new production systems that consider the protection of soil diversity in order to conserve essential ecosystem functions

Species richness and beta diversity patterns of multiple taxa along an elevational gradient in pastured grasslands in the European Alps

Abstract To understand how diversity is distributed in space is a fundamental aim for optimizing future species and community conservation. We examined in parallel species richness and beta diversity components of nine taxonomic groups along a finite space, represented by pastured grasslands along an elevational gradient. Beta diversity, which is assumed to bridge local alpha diversity to regional gamma diversity was partitioned into the two components turnover and nestedness and analyzed at two levels: from the lowest elevation to all other elevations, and between neighboring elevations. Species richness of vascular plants, butterflies, beetles, spiders and earthworms showed a hump-shaped relationship with increasing elevation, while it decreased linearly for grasshoppers and ants, but increased for lichens and bryophytes. For most of the groups, turnover increased with increasing elevational distance along the gradient while nestedness decreased. With regard to step-wise beta diversity, rates of turnover or nestedness did not change notably between neighboring steps for the majority of groups. Our results support the assumption that species communities occupying the same habitat significantly change along elevation, however transition seems to happen continuously and is not detectable between neighboring steps. Our findings, rather than delineating levels of major diversity losses, indicate that conservation actions targeting at a preventive protection for species and their environment in mountainous regions require the consideration of entire spatial settings

A 30-years collection of soil macro-invertebrate abundance data from the European Alps

Here, we present abundance data from 20 soil macro-invertebrate groups from 22 different natural to artificial habitat types in the European Alps. The dataset contains data obtained from soil macro-invertebrate samples (i.e., soil blocks) collected between 1987 and 2020, with the majority of them already published individually in scientific journals. The purpose of this work is to collate the single datasets on Alpine soil macro-invertebrates to one uniform dataset, as such data is only sparsely available. We also want to appreciate the scientific lifework of our mentor and friend, the soil ecologist/soil zoologist Erwin Meyer (1948–2020). The samplings were mainly conducted by Erwin Meyer and his students at the University of Innsbruck (Austria) and Eurac Research (Italy). The assessments of the soil macro-invertebrate communities were part of several sampling campaigns including scientific projects, as well as diploma, master and doctoral theses. The sampling took place mainly during the vegetation period from April to October; in the alpine zone where snow can persist for a long time from June to September. The samples were taken in the following Alpine regions: Vorarlberg and Tirol (Austria), South Tyrol and Trentino (Italy), and the Canton of Uri (Switzerland). The abundance data is given as individuals per square metre (ind./m²) on order level (and species level in case of earthworms). Each row represents one single soil fauna sample. The event code (i.e., representing the different sampling plots) is composed of the sampling region (three letters capitalised), the habitat or plot code (three letters) and the replicate number of these plots (consecutive numbers). Additionally, to the soil fauna data, we present topographic data (elevation, exposition, inclination) as well as habitat classification (e.g., CORINE Land Cover (CLC) nomenclature code) and description

Efficiency of birds as bioindicators for other taxa in mountain farmlands

Biodiversity loss is a global issue, particularly in mountain regions, where land-use/land-cover and climate change dramatically impact on species and communities. Sound ecological research and up-to-date information on biodiversity are needed to support conservation efforts. However, this information is often difficult and costly to obtain. Therefore, bioindicators serve as surrogates to provide information on the entire biocenosis. Birds are considered excellent bioindicators as they occupy different ecological niches and trait spaces.We present a study about the efficiency of birds as bioindicators for the diversity of other taxa in a mountain region in the Central Alps. We surveyed bird communities at 115 sites across a gradient of different grasslands and crops and compared them with the diversity of other taxa (bats, butterflies, grasshoppers, arachnids, and vascular plants). We aimed to identify indicator bird species for grasslands and crops, to assess cross-community concordance between birds and other taxa, and to model the efficiency of bird indices and indicator species as bioindicators of the diversity across habitat types and taxa.We identified indicator bird species for different grassland and crop types and found that efficiency of bird indices and single species varied for habitat types and taxa. We highlight the importance of using carefully selected bioindicators in biodiversity monitoring and conservation planning, and the need for an integrated and interdisciplinary approach for biodiversity research. Moreover, by looking at a combination of different indices we can gain a more comprehensive understanding of ecosystem functioning. We also provide a framework for the use of bird-based monitoring programs and bird-derived indices to guide biodiversity conservation, and emphasise the importance of incorporating different bioindicators into biodiversity research and monitoring to provide a more comprehensive understanding of ecological biodiversity patterns and trends