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Britain's hoverflies : a field guide
'Britain's Hoverflies' is an illustrated photographic field guide to all the genera of hoverflies found in Britain, focusing on the species most likely to be identified. The book also contains distribution maps, phenology charts, and introductory chapters that examine hoverfly biology.
Book
Fit-for-Purpose: Species Distribution Model Performance Depends on Evaluation Criteria - Dutch Hoverflies as a Case Study. e63708
Understanding species distributions and the factors limiting them is an important topic in ecology and conservation, including in nature reserve selection and predicting climate change impacts. While Species Distribution Models (SDM) are the main tool used for these purposes, choosing the best SDM algorithm is not straightforward as these are plentiful and can be applied in many different ways. SDM are used mainly to gain insight in 1) overall species distributions, 2) their past-present-future probability of occurrence and/or 3) to understand their ecological niche limits (also referred to as ecological niche modelling). The fact that these three aims may require different models and outputs is, however, rarely considered and has not been evaluated consistently. Here we use data from a systematically sampled set of species occurrences to specifically test the performance of Species Distribution Models across several commonly used algorithms. Species range in distribution patterns from rare to common and from local to widespread. We compare overall model fit (representing species distribution), the accuracy of the predictions at multiple spatial scales, and the consistency in selection of environmental correlations all across multiple modelling runs. As expected, the choice of modelling algorithm determines model outcome. However, model quality depends not only on the algorithm, but also on the measure of model fit used and the scale at which it is used. Although model fit was higher for the consensus approach and Maxent, Maxent and GAM models were more consistent in estimating local occurrence, while RF and GBM showed higher consistency in environmental variables selection. Model outcomes diverged more for narrowly distributed species than for widespread species. We suggest that matching study aims with modelling approach is essential in Species Distribution Models, and provide suggestions how to do this for different modelling aims and species' data characteristics (i.e. sample size, spatial distribution).
Journal Article
Atlas of the Hoverflies of Greece
The Atlas of the Hoverflies of Greece is a concise presentation of all 418 hoverfly species for Greece known so far. The species are documented with photos and distribution GIS-maps and they are preceded by a general introduction on hoverflies and Greek nature, and a generic key.
eBook
A review of the early stages and host plants of the genera Eumerus and Merodon
The genera Eumerus and Merodon (Diptera: Syrphidae) have a high taxonomic diversity (300+ species altogether), but life histories of most species are unknown. In addition, these hoverfly genera are recognised to be pests (ornamental plants and vegetable crops). In this paper, early stages of four hoverfly species are described, Eumerus hungaricus Szilády, 1940, Eumerus nudus Loew, 1848 and Merodon geniculatus Strobl, 1909, from Spain, and Eumerus strigatus Walker, 1859, from California, USA. Larvae of E. nudus were obtained from swollen roots of Asphodelus cerasiferus J. Gay. Larvae of E. hungaricus were found in bulbs of Narcissus confusus Pugsley. The host plant of the examined specimen of Eumerus strigatus is unknown. Larvae of M. geniculatus were reared from bulbs of different species of Narcissus L. Scanning electron microscope imaging was used to study and illustrate the anterior respiratory processes, pupal spiracles and posterior respiratory processes of the new early stages. A compilation of all available information on the early stages and host plants of Eumerus (21 spp.) and Merodon (15 spp) is provided, as well as an identification key to all known larvae/puparia of these genera. Eumerus elavarensis Séguy, 1961 is proposed as a new synonym of E. hungaricus and first data of this species are reported from Austria, Bulgaria, Spain and Turkey. In Eumerus, larvae are alleged to rely on the previous presence of decay organisms, but in the larvae of E. nudus the sclerotisation and size of the mandibular hooks suggest that this larva can generate decay from intact plant tissue.
Journal Article
Nectar accessibility determines fitness, flower choice and abundance of hoverflies that provide natural pest control
In modern agricultural landscapes, many organisms providing ecosystem services such as pollination and natural pest control are likely constrained by shortage of nectar and/or pollen required for adult nutrition. More and more flower‐rich field margin strips and other habitats are created to eliminate these constraints. For most target organisms, however, it is not well known which (types of) flowers are effective in providing suitable pollen and nectar. We studied the suitability of a wide range of flowers as a food source for zoophagous hoverflies (hoverflies with predatory larvae) at five different levels: nectar accessibility (based on flower morphology), realized adult fitness, flower choice (both based on cage experiments), flower visitation and hoverfly abundance in mixed vegetation (both based on field observations). Realized survival of Episyrphus balteatus is related to effective flower depth by a sigmoid function. The critical flower depth is 1·6 mm, which is less than the proboscis size of the hoverfly. For Asteraceae, the critical floret depth is even less than 1·0 mm, which – in contrast to common knowledge – rules out most species within this family. Both flower choice in the laboratory and flower visitation rates in the field are well correlated with nectar accessibility and realized adult survival. In mixed floral vegetation, the number of zoophagous hoverflies is highly correlated with the abundance of only those flowers that have accessible nectar for these hoverflies. Synthesis and applications. This comparative study demonstrates that nectar (and not pollen) accessibility is the main driver determining flower resource suitability, flower choice and abundance of zoophagous hoverflies in arable field margins. The study identifies the limited range of plant species that can effectively support these beneficial insects. Preserving the right flowers in and around agricultural fields could enhance local populations and the pest control and pollination services they provide.
Journal Article
Tropidia scita (Harris, 1780) (Diptera: Syrphidae), a new hoverfly species for Slovenia
The hoverfly genus Tropidia Meigen, 1822, with the species T. scita (Harris, 1780), is recorded for the first time in the hoverfly fauna of Slovenia. This species was found at Draga ponds near Ig, Slovenia, on the 16th of June, 2024. With this new record, the number of hoverfly species in Slovenia has increased to 363. Rod Tropidia Meigen, 1822 z vrsto T. scita (Harris, 1780) je prvič zabeležen v favni muh trepetavk Slovenije. Ta vrsta je bila najdena 16. junija 2024 na ribnikih v Dragi pri Igu v Sloveniji. S tem novim zapisom se je število vrst muh trepetavk Slovenije povečalo na 363.
Journal Article
Pollination by hoverflies in the Anthropocene
Pollinator declines, changes in land use and climate-induced shifts in phenology have the potential to seriously affect ecosystem function and food security by disrupting pollination services provided by insects. Much of the current research focuses on bees, or groups other insects together as ‘non-bee pollinators’, obscuring the relative contribution of this diverse group of organisms. Prominent among the ‘non-bee pollinators’ are the hoverflies, known to visit at least 72% of global food crops, which we estimate to be worth around US$300 billion per year, together with over 70% of animal pollinated wildflowers. In addition, hoverflies provide ecosystem functions not seen in bees, such as crop protection from pests, recycling of organic matter and long-distance pollen transfer. Migratory species, in particular, can be hugely abundant and unlike many insect pollinators, do not yet appear to be in serious decline. In this review, we contrast the roles of hoverflies and bees as pollinators, discuss the need for research and monitoring of different pollinator responses to anthropogenic change and examine emerging research into large populations of migratory hoverflies, the threats they face and how they might be used to improve sustainable agriculture.
Journal Article
Inferring trends in pollinator distributions across the Neotropics from publicly available data remains challenging despite mobilization efforts
Aim Aggregated species occurrence data are increasingly accessible through public databases for the analysis of temporal trends in the geographic distributions of species. However, biases in these data present challenges for statistical inference. We assessed potential biases in data available through GBIF on the occurrences of four flower‐visiting taxa: bees (Anthophila), hoverflies (Syrphidae), leaf‐nosed bats (Phyllostomidae) and hummingbirds (Trochilidae). We also assessed whether and to what extent data mobilization efforts improved our ability to estimate trends in species' distributions. Location The Neotropics. Methods We used five data‐driven heuristics to screen the data for potential geographic, temporal and taxonomic biases. We began with a continental‐scale assessment of the data for all four taxa. We then identified two recent data mobilization efforts (2021) that drastically increased the quantity of records of bees collected in Chile available through GBIF. We compared the dataset before and after the addition of these new records in terms of their biases and estimated trends in species' distributions. Results We found evidence of potential sampling biases for all taxa. The addition of newly‐mobilized records of bees in Chile decreased some biases but introduced others. Despite increasing the quantity of data for bees in Chile sixfold, estimates of trends in species' distributions derived using the postmobilization dataset were broadly similar to what would have been estimated before their introduction, albeit more precise. Main conclusions Our results highlight the challenges associated with drawing robust inferences about trends in species' distributions using publicly available data. Mobilizing historic records will not always enable trend estimation because more data do not necessarily equal less bias. Analysts should carefully assess their data before conducting analyses: this might enable the estimation of more robust trends and help to identify strategies for effective data mobilization. Our study also reinforces the need for targeted monitoring of pollinators worldwide.
Journal Article
Where is the UK's pollinator biodiversity? The importance of urban areas for flower-visiting insects
Insect pollinators provide a crucial ecosystem service, but are under threat. Urban areas could be important for pollinators, though their value relative to other habitats is poorly known. We compared pollinator communities using quantified flower-visitation networks in 36 sites (each 1 km2) in three landscapes: urban, farmland and nature reserves. Overall, flower-visitor abundance and species richness did not differ significantly between the three landscape types. Bee abundance did not differ between landscapes, but bee species richness was higher in urban areas than farmland. Hoverfly abundance was higher in farmland and nature reserves than urban sites, but species richness did not differ significantly. While urban pollinator assemblages were more homogeneous across space than those in farmland or nature reserves, there was no significant difference in the numbers of rarer species between the three landscapes. Network-level specialization was higher in farmland than urban sites. Relative to other habitats, urban visitors foraged from a greater number of plant species (higher generality) but also visited a lower proportion of available plant species (higher specialization), both possibly driven by higher urban plant richness. Urban areas are growing, and improving their value for pollinators should be part of any national strategy to conserve and restore pollinators.
Journal Article