Semi‐natural habitats provide important resources for wild bees in agricultural landscapes. Landscapes under management are dynamic and floral resources fluctuate in space and time. Thus, promoting ...different semi‐natural habitat types within landscapes could be key to support diverse bee meta‐communities throughout the season.
Here, we integrate analyses of α‐diversity (species richness) and β‐diversity and species‐habitat networks to examine the relative contribution of all major semi‐natural habitats to wild bee meta‐communities in agricultural landscapes. We sampled extensively and conventionally managed meadows, flower strips, hedgerows and forest edges in spring, early and late summer in 25 landscapes in Switzerland.
Habitat types varied in their importance for wild bees throughout the season: While extensively managed meadows supported more rare species, habitat specialists and bee species overall than the other habitat types, flower strips were most important later in the season. Each of the five investigated habitat types harboured relatively unique sets of species with different habitats generally acting as distinct modules in the overall bee‐habitat network.
Not only flower richness in a habitat per se, but also flower‐habitat network properties (habitat strength and functional complementarity) were good predictors of wild bee richness. In addition to local floral richness, landscape composition and configuration interactively influenced β‐diversity patterns across habitats.
Synthesis and applications. Our study highlights the value of pollinator‐habitat network analysis to inform pollinator conservation management at the landscape scale, especially when combined with information on floral resources and flower‐habitat networks. Maintaining different types of semi‐natural habitats offers diverse and complementary resources throughout the season, which are crucial to sustain diverse wild bee meta‐communities in agricultural landscapes. Particularly meadow extensification schemes can play a key role in safeguarding rare and specialist species in these landscapes. While locally a high flower richness promoted bee abundance and richness in general, our results indicate that increasing connectivity between habitat patches in landscapes dominated by arable crops appears to improve species exchange between local bee communities of different habitats, thereby possibly increasing their resilience to disturbances.
Zusammenfassung
Naturnahe Lebensräume bieten wichtige Ressourcen für Wildbienen in Agrarlandschaften. Diese bewirtschafteten Landschaften sind jedoch dynamisch, und die Verfügbarkeit von Ressourcen wie Blütenpflanzen kann stark variieren. Daher könnte die Förderung verschiedener Typen von naturnahen Lebensräumen der Schlüssel sein für den ganzjährigen Schutz artenreicher Wildbienengemeinschaften.
In dieser Studie analysieren wir α‐Diversität (Artenzahl), β‐Diversität (Ähnlichkeit der Artzusammensetzung) und Art‐Lebensraum‐Netzwerke, um die relative Wichtigkeit der häufigsten naturnahen Lebensräume in Agrarlandschaften für artenreiche Wildbienengemeinschaften zu untersuchen. In 25 Landschaften in der Schweiz sammelten wir Daten zu Wildbienenarten in extensiv und konventionell bewirtschafteten Wiesen, Buntbrachen, an Hecken und Waldrändern im Frühling, Früh‐ und Spätsommer.
Die verschiedenen Lebensraumtypen waren von unterschiedlicher Wichtigkeit für Wildbienen, je nach Zeitpunkt in der Saison. Während extensiv bewirtschaftete Wiesen generell mehr seltene Arten, Lebensraumspezialisten und mehr Bienenarten beherbergten als die anderen Lebensraumtypen, waren Buntbrachen vor allem im Juli wichtig. In jedem der fünf untersuchten Lebensraumtypen fanden wir eine relativ einzigartige Artzusammensetzung: Im Bienen‐Lebensraum‐Netzwerk gliederten sich die Lebensraumtypen in verschiedene Module.
Nicht nur Blütenpflanzenvielfalt in einem Lebensraum, sondern auch Blütenpflanzen‐Lebensraum‐Netzwerk Eigenschaften («Lebensraum‐Stärke» und «funktionelle Komplementarität») konnten die Wildbienenvielfalt in einem Lebensraum voraussagen. Zusätzlich zur lokalen Blütenpflanzenvielfalt beeinflussten die Landschaftszusammensetzung und ‐konfiguration die β‐Diversität der Wildbienen (Ähnlichkeit der Artzusammensetzung) zwischen den Lebensraumtypen.
Unsere Studie unterstreicht den Wert der Analyse von Bestäuber‐Lebensraum‐Netzwerken für die Förderung und den Schutz der Bestäuber auf Landschaftsebene, insbesondere in Kombination mit Informationen zu Ressourcen wie Blütenpflanzen. Die Erhaltung verschiedener Typen naturnaher Lebensräume bietet während der gesamten Saison vielfältige und sich ergänzende Ressourcen, die für die Erhaltung vielfältiger Wildbienengemeinschaften in Agrarlandschaften von entscheidender Bedeutung sind. Insbesondere Massnahmen zur Extensivierung von Wiesen können eine Schlüsselrolle beim Schutz seltener und spezialisierter Arten in diesen Landschaften spielen. Während eine lokal hohe Blütenpflanzenvielfalt die Anzahl und Vielfalt der Wildbienen im Allgemeinen fördert, kann eine bessere Vernetzung der Lebensräume in von Ackerbau dominierten Landschaften den Artenaustausch zwischen lokalen Bienengemeinschaften verbessern. Dies erhöht möglicherweise die Widerstandsfähigkeit der Wildbienengemeinschaften gegenüber Störungen.
Our study highlights the value of pollinator‐habitat network analysis to inform pollinator conservation management at the landscape scale, especially when combined with information on floral resources and flower‐habitat networks. Maintaining different types of semi‐natural habitats offers diverse and complementary resources throughout the season, which are crucial to sustain diverse wild bee meta‐communities in agricultural landscapes. Particularly meadow extensification schemes can play a key role in safeguarding rare and specialist species in these landscapes. While locally a high flower richness promoted bee abundance and richness in general, our results indicate that increasing connectivity between habitat patches in landscapes dominated by arable crops appears to improve species exchange between local bee communities of different habitats, thereby possibly increasing their resilience to disturbances.
1. For managed temperate forests, conservationists and policymakers favour finegrained uneven-aged (UEA) management over more traditional coarse-grained even-aged (EA) management, based on the ...assumption that within-stand habitat heterogeneity enhances biodiversity. There is, however, little empirical evidence to support this assumption. We investigated for the first time how differently grained forest management systems affect the biodiversity of multiple above- and below-ground taxa across spatial scales. 2. We sampled 15 taxa of animals, plants, fungi and bacteria within the largest contiguous beech forest landscape of Germany and classified them into functional groups. Selected forest stands have been managed for more than a century at different spatial grains. The EA (coarse-grained management) and UEA (fine-grained) forests are comparable in spatial arrangement, climate and soil conditions. These were compared to forests of a nearby national park that have been unmanaged for at least 20 years. We used diversity accumulation curves to compare γ-diversity for Hill numbers ⁰D (species richness), ¹D (Shannon diversity) and ²D (Simpson diversity) between the management systems. Beta diversity was quantified as multiplesite dissimilarity. 3. Gamma diversity was higher in EA than in UEA forests for at least one of the three Hill numbers for six taxa (up to 77%), while eight showed no difference. Only bacteria showed the opposite pattern. Higher γ-diversity in EA forests was also found for forest specialists and saproxylic beetles. 4. Between-stand β-diversity was higher in EA than in UEA forests for one-third (all species) and half (forest specialists) of all taxa, driven by environmental heterogeneity between age-classes, while α-diversity showed no directional response across taxa or for forest specialists. 5. Synthesis and applications. Comparing EA and uneven-aged forest management in Central European beech forests, our results show that a mosaic of different ageclasses is more important for regional biodiversity than high within-stand heterogeneity. We suggest reconsidering the current trend of replacing even-aged management in temperate forests. Instead, the variability of stages and stand structures should be increased to promote landscape-scale biodiversity.
Realistic measures of biodiversity should reflect not only the relative abundances of species, but also the differences between them. We present a natural family of diversity measures taking both ...factors into account. This is not just another addition to the already long list of diversity indices. Instead, a single formula subsumes many of the most popular indices, including Shannon's, Simpson's, species richness, and Rao's quadratic entropy. These popular indices can then be used and understood in a unified way, and the relationships between them are made plain. The new measures are, moreover, effective numbers, so that percentage changes and ratio comparisons of diversity value are meaningful.
We advocate the use of diversity profiles, which provide a faithful graphical representation of the shape of a community; they show how the perceived diversity changes as the emphasis shifts from rare to common species. Communities can usefully be compared by comparing their diversity profiles. We show by example that this is a far more subtle method than any relying on a single statistic.
Some ecologists view diversity indices with suspicion, questioning whether they are biologically meaningful. By dropping the naive assumption that distinct species have nothing in common, working with effective numbers, and using diversity profiles, we arrive at a system of diversity measurement that should lay much of this suspicion to rest.
Species richness increases with energy availability, yet there is little consensus as to the exact processes driving this species–energy relationship. The most straightforward explanation is the ...more‐individuals hypothesis (MIH). It states that higher energy availability promotes a higher total number of individuals in a community, which consequently increases species richness by allowing for a greater number of species with viable populations. Empirical support for the MIH is mixed, partially due to the lack of proper formalisation of the MIH and consequent confusion as to its exact predictions. Here, we review the evidence of the MIH and evaluate the reliability of various predictions that have been tested. There is only limited evidence that spatial variation in species richness is driven by variation in the total number of individuals. There are also problems with measures of energy availability, with scale‐dependence, and with the direction of causality, as the total number of individuals may sometimes itself be driven by the number of species. However, even in such a case the total number of individuals may be involved in diversity regulation. We propose a formal theory that encompasses these processes, clarifying how the different factors affecting diversity dynamics can be disentangled.
We evaluated how the taxonomic, phylogenetic and functional diversities of butterflies and their community-weighted traits are affected by urbanization in the southeastern Brazilian Atlantic Forest. ...For this purpose, a dataset of Nymphalidae species distributed across 15 urban, semiurban, and rural fragments was analyzed. Urbanization was defined by a set of environmental variables. Furthermore, the total area of each fragment was also considered in the analyses but did not influence the results, in which disturbance level and patch connectivity drove the environmental variation across the urban matrix. Species diversity increased towards the more connected fragments, while phylogenetic and functional diversity did not vary in relation to urbanization. A high forewing:hindwing ratio and the frequency of tiger-like wings were positively related to the urban fragments, while a low forewing:hindwing ratio and iridescent wings were related to the semiurban and rural fragments. The suitability of highly interconnected rural habitats for the maintenance of butterfly diversity was corroborated as expected. Nonetheless, our results also showed that semiurban fragments preserved the ecologically relevant traits of butterflies related to forested habitats, expressed in butterfly groups possibly linked with dispersal capability to avoid predation. Careful management of semiurban fragments and urban landscaping, including highly structured and native vegetation outside urban parks, may increase the functional and taxonomic diversities or at least maintain the current levels of functionality in the urban matrix. Thus, it is possible to preserve the biological diversity of native fauna and flora and recover relevant ecosystem services, ensuring the conservation of Neotropical urban centers.
This open access book brings together different perspectives on migration and the city that are usually discussed separately, to show the special character of the urban context as a territorial and ...political space where people coexist, whether by choice or necessity. Drawing on heterogeneous situations in cities in different world regions (including Europe, North America, the Middle East, South, Southeast and East Asia and the Asia Pacific) contributions to this volume examine how migration and the urban context interact in the twenty-first century. The book is structured in four parts. The first looks at cities as hubs of cultural creativity, exploring the many dimensions of cultural diversity and identity as they are negotiated in the urban context. The second focuses on what lies outside the large urban centres of today, notably suburbs, while the third part engages with migration and diversity in small and mid-sized cities, many of which have adopted strategies to welcome growing numbers of migrants. Last but not least, the fourth part looks at the challenges and opportunities that asylum-seeking and irregular migration flows bring to cities. By providing a variety of empirical cases based on various world regions, this book is a valuable resource for researchers, students and policy makers.
While more and more studies are exploring the application of remote sensing in assessing biodiversity for different ecosystems, most consider biodiversity at one point in time. Using several ...remote-sensing-based metrics, we asked how well remote sensing can detect biodiversity (both α- and β-diversity) in a prairie grassland across time using airborne hyperspectral data collected in two successive years (2017 and 2018) and at different periods in the growing season (2018). The ability to detect biodiversity using “spectral diversity” and “spectral species” types indeed varied significantly over a 2-yr timespan. Toward the end of the growing season in 2018, the relationship between field- and remote-sensing-based α- and β-diversity weakened compared to data collected from the same season in the previous year. This contrasting pattern between the two years was likely influenced by prescribed fire, altered weather, and the resulting shifting species composition and phenology. These findings indicate that direct detection of α- and β-diversity in grasslands should be multi-temporal when possible and should consider the effect of disturbances, climate variables, and phenology. We demonstrate an essential role for airborne platforms in developing a global biodiversity monitoring system involving forthcoming space-borne hyperspectral sensors.
Fires, either natural or prescribed, are essential for conserving pyrogenic ecosystems; however, climate change is predicted to increase fire severity possibly causing negative impacts on native ...species diversity. Reptile and amphibian species may be particularly at risk given they are ectothermic species. The objective of this study was to better understand the impacts of fire severity on the herpetofaunal communities of the Florida scrub. The Florida scrub is an imperiled ecosystem that sustains over two-thirds of listed reptiles and amphibians in Florida. We conducted a field-based study to test taxonomic and functional diversity differences across four varying fire severities: unburned, low, medium and high. We also examined the association between herpetofaunal diversity and microhabitat variables across fire severities. We recorded 549 individuals, representing 23 reptile and amphibian species. The herpetofaunal community was not significantly different between the varying fire severities; however, a congruent trend occurred with the greatest diversity occurring at the intermediate fire severity plots. In addition, we showed leaf litter was significantly associated with species diversity. Interesting, the endangered sand skink,
Plestiodon reynoldsi,
was not recorded at the high fire severity plots, which could have implications on fire management practices of this federally threatened species. In this study, we demonstrated fire severity does not have a direct but instead an indirect effect on the native herpetofaunal species diversity in the Florida scrub. Thus, increasing fire severity consumption of leaf litter has the potential to detrimentally impact the Florida scrub herpetofaunal diversity. This study highlights the importance of fine-scale microhabitat variables, such as leaf litter, as an important indicator for biodiversity conservation.
A large number of diversity metrics are available to study and monitor biodiversity, and their responses to biodiversity changes are not necessarily coherent with each other. The choice of ...biodiversity metrics may thus strongly affect our interpretation of biodiversity change and, hence, prioritization of resources for conservation. Therefore it is crucial to understand which metrics respond to certain changes, are the most sensitive to change, show consistent responses across different communities, detect early signals of species decline, and are insensitive to demographic stochasticity. Here we generated synthetic communities and simulated changes in their composition according to 9 scenarios of biodiversity change to investigate the behaviour of 12 biodiversity metrics. Metrics showed diverse abilities to detect changes under different scenarios. Sørensen similarity index, arithmetic and geometric mean abundance, and species and functional richness were the most sensitive to community changes. Sørensen similarity index, species richness and geometric abundance showed consistent responses across all simulated communities and scenarios. Sørensen similarity index and geometric mean abundance were able to detect early signals of species decline. Geometric mean abundance, and functional evenness under certain scenarios, had the greatest ability to distinguish directional trends from stochastic changes, but Sørensen similarity index and geometric mean abundance were the only indices to show consistent signals under all replicates and scenarios. Classic abundance-weighted heterogeneity indices (e.g. Shannon index) were insensitive to certain changes or showed misleading responses, and are therefore unsuitable for comparison of biological communities. We therefore suggest that separate metrics of species composition, richness, and abundance should be reported instead of (or in addition to) composite metrics like the Shannon index.
•Synthetic communities are used to explore the behaviour of 12 biodiversity metrics.•Metrics behaviour is assessed under different scenarios of biodiversity change.•Abundance-weighted heterogeneity metrics are unsuitable for biodiversity monitoring.•Sørensen similarity index and geometric mean abundance show desirable properties.•Separate metrics of species composition and abundance should be reported.
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