Monitoring the spread of sculptured resin bee (Megachile sculpturalis) in Southeast Europe
Centre for Bee Research, Faculty of Biology, University of Belgrade
Distribution of sculptured resin bee in Europe and Serbia
Sculptured resin bee (Megachile sculpturalis Smith, 1853) belongs to the Megachilidae family (Hymenoptera: Anthophila). This numerous and diverse family of solitary bees includes several economically important species domesticated for pollination of certain agricultural crops, like bees from genus Megachile (M. rotundata - alfalfa leafcutting bee), and so-called orchard bees (Osmia bicornis, O. cornuta). There are 35 genera with over 450 species from this family in Europe (Rasmont et al. 2017), while in Southeast Europe there are 24 genera and over 300 species (Kuhlmann et al. 2015), of which over 170 species are present in Serbia (35 species only from genus Megachile).
Sculptured resin bee is originally distributed in the temperate and subtropical areas of East Asia (Japan, China, Korea). It was first recorded outside its natural range in 1994 in eastern North America (North Carolina). Since then, it has successfully spread across the continent and it is now present in almost all states in the eastern half of the United States, as well as in southern Canada (Parys et al. 2015; Ascher & Pickering 2020).
In Europe, it was first detected in 2008 in southern France, and soon after in Italy (2009) and Switzerland (2010), and for now, the origin of this second introduction has not been determined (whether it was from from Asia or America). In the meantime, the species has spread to 9 more European countries: Spain, Andorra, Germany, Austria, Slovenia, Croatia, Hungary, Serbia and the Crimea.
As with other introduced species, range expansion is a combination of different dispersion mechanisms, so the dynamics and the order of the occupation of different territories show a mixture of both expected progressions and unexpected jumps, with obvious avoidance of the Alps and other high mountain areas.
Selected maps show a schematic reconstruction of selected phases of expansion, as well as overview for 2019.
Maps taken from Bila Dubaić J., Lanner J., Plećaš M., Raičević J. & Ćetković A. 2021. Asian bee Megachile sculpturalis (Hymenoptera: Megachilidae) jumping and sneaking further eastwards through Europe: a retrospective from the Serbian perspective, as of 2019. (in prep.)
In Serbia, sculptured resin bee was first recorded in 2017, in the center of Belgrade. Since then, we have been monitoring its spread, and finally in the summer of 2019 we have confirmed that the species has successfully established in Serbia. For now, it is with certainty detected only in the wider area of Belgrade, but in large numbers.
Our next important task is to study its probable presence and status of populations in other parts of Serbia, and possibly to detect the trends of expansion in the Balkans. Data on the spread of this species in Europe so far suggest that it most successfully conquers urban areas, mainly because of the availability of mass-planted exotic plants, whose pollen is basis of its offspring's diet.
Autokomanda (Belgrade) 02.08.2019.
Overview of the plants which this bee species uses in different parts of newly inhabited areas (in North America and Europe), so far provides a completely unclear picture of plant's relative impact on its success and invasiveness. Therefore, it is of great scientific importance to examine how different plants or habitat types contribute to the spread of this bee in Serbia or in any other newly invaded area. In addition to urban areas, as of summer 2020, we are trying to monitor its occurrence in rural, semi-natural and natural habitats, throughout our country.
You can help us in the search for this bee!
Locations where sculptured resin bees was recorded in Belgrade 2017–2019, in relation to the surveyed Japanese pagoda trees sites (based on: Bila Dubaić et al. 2021a).
Bila Dubaić J., Plećaš M., Raičević J. & Ćetković A. 2021. Early-phase colonization by introduced Asian bee (Hymenoptera: Megachilidae: Megachile sculpturalis) revealed by local floral resources variability (in rev.)
Ecology and bionomy
Megachile sculpturalis is the first non-native (allochtonous) bee species in Europe. Term allochtonous refers to a species that is not naturally inhabiting a certain area, but have arrived with the help of humans from another (usually very distant) region. Interestingly, there is a significant difference in the number and proportion of introduced bee species between two large continental areas of the northern temperate zone. In North America at least 55 such species have been identified, within a native fauna of about 4,000 species, while European fauna with about 2,050 native species includes only a few exotic bees, mostly of very limited and/or peripheral distribution and unclear status (Ebmer 2011; Russo 2016; Rasmont et al. 2017).
Knowledge on the bionomy and ecology of sculptured resin bee in newly inhabited areas is still insufficient, as well as information on the impact this species can have on domestic (autochthonous) bee fauna. So far, there have been reports of aggressive eviction of native bees from several genera (Megachile, Osmia and Xylocopa) from their nests by sculptured resin bee (Gibbs et al. 2017; Le Feon et al. 2018). However, it has not yet been adequately studied whether such behavior can have significant negative effects on the native bee populations.
It is suggested that sculptured resin bee can also promote reproduction and spread of the invasive plant species. However, there are no clear indicators to confirm this potentially harmful phenomenon. Speed at which this species spreads and its success in invading new areas (North America and Europe), as well as large numbers that are occasionally registered, label this species with a negative term invasive, i.e. potentially harmful and dangerous to the survival or functioning of certain native species, trophic networks or ecosystems. This is why it is important to carefully monitor every insufficiently studied exotic species in newly inhabited areas.
Sculptured resin bee female preparing the nest
In the temperate zone, adult activity of this bee begins in late spring (usually mid-June) and lasts almost until the end of summer (mostly July-August, only exceptionally until mid-September). This is a solitary bee, which means that every female makes (on her own) separate nests for each of her offspring. (MP: Ali ne pravi za svako jaje. Trebalo bi ta bude valjda ...every female makes (on her own) separate nest for their offspring)
For nesting, they choose pre exiting tunnel-like cavities, in solid wood or hollow stems, usually 10-12 mm in diameter. For each laid egg, they make a separate cell that they supply with food - mixture of pollen and nectar. After filling the entire tunnel, they close the opening with a mixture of mud and resin. The resin is collected from various trees, and this is why they are called resin bees. Soon after the egg is laid, the larva hatches - they are poorly motile, remain in their nest chamber, feeding on the supplies that their mother provided. These insects spend winter in the prepupal stage. Transformation into the next phase of development (pupa) occurs in the spring. Metamorphosis into adult individuals take place at the beginning of the summer, after which they hatch from the nest. This is followed by the search for the partner and mating, and a new annual cycle begins.
Life cycle of sculptured resin bees involves long periods of dormancy in a substrate that can easily and safely be transported over long distances, as part of commercial activities (trade of suitable timber materials, tubular reed and bamboo stems, etc.). It is proven that this accelerates secondary passive spread of this species. In fact, the appearance (emergence) of this species in any new area that is relatively distant from the nearest inhabited zone (as a possible source of new introduction), does not necessarily occur according to the "expected" model of gradual continuous expansion. Apparently, invasion of any new area could also happen by long-distance jump-dispersal from any "hot spot" with a high local population abundance, which means from any part of any of the currently inhabited continents! Today, a sophisticated genetic methods are available for more detailed reconstruction of the allochthonous range expansion pathways.
To understand the ecology and bionomy of any bee species, it is important to determine plants that it uses as food source, and which it potentially pollinates. Depending on whether it uses more narrow or wide range of plants from different groups (one or more genera or families) a bee species can be labeled a specialist ("oligolectic") or a generalist ("polylectic"). It is important to stress out that these terms refer exclusively to pollen utilization - larval food. It is known that some bees, if they have no other choice, occasionally collect pollen that is less suitable for the development of their larvae, which can lead to their high mortality. On the other hand, many species visit a much wider range of plants as a nectar source, i.e. to provide energy for the daily activities of adults, and in this respect they are much less picky.
Therefore, it is especially important to understand these trophic interactions in the context of the expansion of the range of this introduced species, i.e. in each newly inhabited area. In today's entire invaded area, sculptured resin bee has been so far recorded on a wide range of plants (over 70 genera, at least 24 families). However, the pollen collecting activity has not been documented on most of them.
Quantitative review of documented visitation to plants of different families within the invasion area in America and Europe.
Summary review of M. sculpturalis visitation to plants of different families: (A) number of recording localities compiled for the entire invasion range, and separately by respective continents (ranked in descending order of total values); 9 families (out of 24) represented with only a single recorded locality are shown through cumulative values; (B) visits which included female bee records, shown through numbers of localities (LOCs) for all records and those which included evidenced female/s (ranked in descending order of female-included records); for only 7 plant families (out of 16) recording included documented pollen collecting (values represent number of respective localities) (Bila Dubaić et al. 2021).
Only by analyzing the pollen (collected directly from females or from newly formed nests) we can identify the importance that certain plant has for larvae, and for successful population growth of this bee species. However, many plants that are widely present and frequently visited can be useful to us when determining the presence and exploring the number of sculptured resin bees (regardless of whether they use them for feeding their offspring or just as a nectar source). A number of exotic, decorative plants, which bloom profusely in the summer months, are potentially important for monitoring the dynamics of the spread of this species, primarily in urban areas. In Europe, the sculptured resin bee was recorded on at least 39 genera from 14 plant families, of which 4 exotic and 2 native (autochthonous) genera of plants stand out for Serbia.
Most important plants for spotting and monitoring sculptured resin bee in Serbia
Japanese pagoda tree
(Styphnolobium = Sophora)
Determine the status of presence and monitor the spread of this bee species in Serbia (and in the region).
Monitor the population dynamics of this species
Record and quantify interactions with exotic and native plants, evaluate the nature of interactions and possible effects - negative or positive (pollination, propagation, etc.).
Evaluate the nature of interactions with other wild and managed bee species (on individual and community level), i.e. possible negative or positive effects.
By using methods of genetic analysis examine (a) the population history and demographics of local and regional spread, and (b) trophic interactions with plants
Methodology and structure of the project
(note: in preparation)
The definitive structure and methodology will be developed in phases and tested during the 2020 season. This is the first calendar year we are entering with reliable evidence of established and stable populations of this bee in Serbia.
An important aspect of our work in the season of 2020 was the organization and implementation of "Citizen Science Project - CSP", as an important prerequisite for the comprehensive implementation of key aspects of the project.
Project participants and funding
(note: in preparation)
Scientific and research institutions
Faculty of Biology, University of Belgrade (CBB)
Prof. dr Ljubiša Stanisavljević, (Head of the Center)
Doc. dr Aleksandar Ćetković, (Coordinator of the main Project) (MP: ja bih ostavio samo project)
Jovana Bila Dubaić, Research Assistant (coordinator of CSP)
Jovana Raičević, Research Trainee
Nenad Lazarević, (technical assistant)
Faculty of Forestry, University of Belgrade
Faculty of Sciences and Mathematics, University of Niš
Other institutions, organizations, companies
The project of monitoring the spread of sculptured resin bee in Serbia is currently being implemented without asserted funding. With regular institutional and logistical support for the work of the Center for Bee Biology (CBB) by the Faculty of Biology, individual researchers have secured partial funding of ongoing activities through various independent or parallel scientific or professional projects, in areas compatible with activities under this project. A large part of current and planned activities is volunteer work of participants from these institutions and organizations. In the future, there is a possibility of applying for aimed funding for later phases of the project.
Ćetković, A., Stanisavljević, L., Plećaš, M., Raičević, J., Žikić, V., Glavendekić, M. & Bila Dubaić, J. (2020) Project: Monitoring the spread of sculptured resin bee (Megachile sculpturalis) in Serbia. Centar za biologiju pčela, Biološki fakultet, Univerzitet u Beogradu. [https://sites.google.com/bio.bg.ac.rs/srbee/english?authuser=0]
News, results, reports, publicatons
Project: Monitoring the spread of sculptured resin bee in Austria and Switzerland "Asiatische Mörtelbiene"
"Asiatische Mörtelbiene" video presented at conference "CitSci Helvetia 2021 - Connecting Citizen Science in Switzerland" (*in English*) (*in German*)
Monitoring the spread of sculptured resin bee in Germany (and Europe)