Biodiversity Data Journal :
Research Article
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Corresponding author: Enrico Ruzzier (enrico.ruzzier@unipd.it)
Academic editor: Matthew Yoder
Received: 19 Aug 2020 | Accepted: 23 Nov 2020 | Published: 26 Nov 2020
© 2020 Enrico Ruzzier, Mattia Menchetti, Laura Bortolotti, Marco Selis, Elisa Monterastelli, Leonardo Forbicioni
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ruzzier E, Menchetti M, Bortolotti L, Selis M, Monterastelli E, Forbicioni L (2020) Updated distribution of the invasive Megachile sculpturalis (Hymenoptera: Megachilidae) in Italy and its first record on a Mediterranean island. Biodiversity Data Journal 8: e57783. https://doi.org/10.3897/BDJ.8.e57783
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Megachile sculpturalis (Smith, 1853) (Hymenoptera: Megachilidae) is an invasive solitary bee that is rapidly spreading all over Europe. The present study aims to update the distribution of this species in Italy. The research led to the collection of 177 records, obtained through bibliographic research and data-mining from websites, blogs and social networks. We here present the first record of M. sculpturalis on a Mediterranean island and discuss its possible effect on the native ecosystem. Given the particular discovery of M. sculpturalis on Elba Island (Tuscany), we suggest possible monitoring, containment and possible eradication measures of the species.
biodiversity loss, early detection, invasive species, island, native plants, pollinators
Invasive alien species are a threat to native biodiversity (
Megachile Latreille, 1802 (Megachilidae: Megachilini) is a rather specious genus of solitary bees with introduced species in almost all continents (e.g.
Since no exhaustive reference exists about the real extent of the invasion of M. sculpturalis in the Italian peninsula, we decided to conduct extensive research in order to fill the knowledge gap and to update the distribution of this invasive species. In particular, we give emphasis to the discovery of M. sculpturalis on Elba Island (Tuscan Archipelago), the first case of an exotic bee on a Mediterranean island and discuss the possible effects on the native flora and fauna. Given the uniqueness of the discovery, we suggest how Elba Island and the Tuscan Archipelago National Park may become a model for monitoring, controlling and even eradicating this invasive bee in island ecosystems.
In order to have the most efficient and extensive data collection, we adopted a mixed data search approach: literature review, direct observation, data-mining and dedicated websites. Direct observations were recorded through active research by the authors or via communication with other entomologists. Further data were mined from national entomological and naturalists’ online forums (“Forum Entomologi Italiani”, “Forum Natura Mediterraneo”), Facebook groups (“Entomologia, Insetti e altri Artropodi”, “Insetti e Aracnidi Italiani”) and national and international citizens' science websites (iNaturalist.org, Beewatching.it, Stopvelutina.it). All the data collected are updated to December 2019. In the final database, we included only records verified by the authors through pictures, in possession of the precise location and other relevant information. For each observation, we recorded the date, locality [name], GPS coordinates (if available), number of observed specimens (if defined), landscape context, data source, nesting observations (bee hotels or natural nests) and flower interactions. Since it was not always possible to identify the sex of the specimens, the sex category was not included in the analysis.
All the data collected are available in Suppl. material
The maps have been made with QGIS (v. 3.4.2-Madeira) using a raster layer freely available on Natural Earth (www.naturalearthdata.com) and later edited with Adobe Illustrator CC 2019.
A tissue sample of one of the specimens collected on Elba Island was sent to and sequenced at the Canadian Centre for DNA Barcoding (CCDB, Biodiversity Institute of Ontario, University of Guelph). DNA sequencing resulted in a COI barcode fragment of 658 bp. The sequence, named MOLTE082-19, is privately stored as part of the project “MOLTE” in the Barcode of Life Data Systems (BOLD; Ratnasingham and Hebert 2007). The integrated bioinformatics platform BOLD was used to assess the identity of the sequence obtained. Furthermore, the sequence was compared to six M. sculpturalis sequences available in BOLD, namely ABBOL043-15; BCT012-06; BEECA275-06; BEECA276-06; GBMIN78089-17 and MOLTE077-19. These barcodes represent processed IDs in BOLD and are grouped under the Barcode Index Number (BIN) BOLD:AAE8645. The pairwise genetic distances between sequences were calculated using MEGA X software, under default settings (
The survey produced 177 records covering most of the Italian peninsula. Northern regions present the highest percentage of observations (80.2% of the total), respectively: 33 (Lombardy), 31 (Emilia-Romagna), 22 (Veneto), 21 (Liguria), 16 (Piedmont), 12 (Trentino-Alto Adige) and 7 (Friuli-Venezia Giulia). Central Italy proved to be just as colonised although, to a lesser extent (18.1%): 22 (Tuscany), 5 (Lazio), 3 (Abruzzo), 1 (Marche) and 1 (Umbria) while three regions in the South (Campania, Calabria and Basilicata) possess one record each (1.7%). So far, the species is not yet recorded in Valle d’Aosta, Molise, Sicily and Sardinia. Data show that the number of reports increased exponentially from the sporadic reports per year between 2009 and 2015, to 11, 21, 39, 97 reports in 2016, 2017, 2018 and 2019, respectively.
Analysing the sources of our data, Facebook results in the primary source of records (49, about the 27.7% of the total), followed by direct observations (41, 23%), iNaturalist (39, 22%), Beewatching (13, 7.3%), literature review (17, 9.6%), online forums (10, 5.6%) and Stopvelutina website (8, 4.5%) .
The altitudes at which M. sculpturalis was recorded range from the sea level (~ 1 m) up to slightly above 1400 m (max. 1421 m a.s.l.), with an average of 212.3 m. Most of the reports come from plain areas, 68 of which were below 50 m a.s.l. (38.4%) and 62 comprised between 50 and 300 m a.s.l. (35%); 33 reports come from hilly areas between 300 and 700 m a.s.l. (18.6%) and 12 from mountain locations above 700 m a.s.l. (6.8%), five of which are above 1000 m.
Observations present a peak of detections in July (113, 63.8%) followed by August (49, 27.7%), June (13, 7.3%) and September (2, 1.1%).
Regarding the landscape, most of the observations were made in rural areas (91, 51.4%), followed by the urban (69, 38.9%) and natural environment (17, 9.6%).
In 68 cases out of 177 (38.4%), the foraging behaviour of M. sculpturalis was observed and the visited plant were recorded. Lavandula sp. L. (Lamiaceae) is the most visited plant with 26 observations (38.2%), followed by Wisteria spp. (Wisteria sp. Nutt. + Wisteria sinensis (Sims) DC + Wisteria floribunda (Willd.) DC.) (Fabaceae) with 10 cases (14.7%). The other observations identified: Syringa sp. L. (Oleaceae) (4), Vitex agnus-castus L. (Lamiaceae) (4), Chamaerion angustifolium (L.) Scop. (Onagraceae) (3), Cirsium sp. Mill. (Asteraceae) (3), Citrus spp. (Citrus sp. L. + Citrus japonica Thunb.) (Rutaceae) (2), Styphnolobium japonicum (L.) Schott (Fabaceae) (2), Cichorium intybus L. (Asteraceae) (1), Cirsium arvense (L.) Scop. (Asteraceae) (1), Firmiana platanifolia (L.) W. Wight (Malvaceae) (1), Helianthus annuus L. (Asteraceae) (1), Koelreuteria paniculata Laxm. (Sapindaceae) (1), Lavandula angustifolia Mill. (Lamiaceae)(1), Ligustrum lucidum W.T. Aiton (Oleaceae) (1), Rubus sp. L. (Rosaceae) (1), Scabiosa sp. L. (Caprifoliaceae) (1), Tetradium daniellii (Benn.) T.G. Hartley (Rutaceae) (1), Trifolium pratense L. (Fabaceae) (1) and unidentified plants (3). A total of 37 nesting reports were done in bee hotels (20.9%), with 21 in natural cavities (11.8%).
Literature review and our data allowed the identification of the most commonly visited genera of plants all over the invaded range:
Styphnolobium spp. Schott (Fabaceae) (
Since its first discovery in Italy in 2009 (
The first specimen of M. sculpturalis (male) was collected in Rio, loc. Nisportino, on 16 August 2019, (
Since Nisportino is a small village, geographically isolated from any important port and visited mainly by tourists, it is plausible that the introduction of M. sculpturalis could have occurred only locally and accidentally by transport of commodities; this hypothesis is suggested by the tendency of M. sculpturalis to nest, in absence of natural wood cavities, in plastic tubes, brick holes and other opportunistic shelters (
In the near future, newly available DNA barcodes of M. sculpturalis from both the native and introduced areas will substantially contribute to clarify the relationships between the various populations and possibly highlight the main pathways of national and transnational introduction of the species. In particular, the complete haplotypes' characterisation of the population inhabiting the Italian peninsula may help to clarify if the current population is the result of multiple independent introduction events or if it is, instead, attributable to a single or a small group of founders. In addition to DNA barcodes, the usage of multiple and more informative genetic markers may constitute a powerful tool to reconstruct the invasion pattern of this species determining the population of origin and the source of introduction for all locations on a global scale.
Understanding this process could help the development of more effective control systems in limiting the spread of M. sculpturalis and, in particular, preventing its introduction into territories where it is still absent. With specific reference to our case, if not managed in an appropriate way, M. sculpturalis could spread amongst the islands of the archipelago and, in the same way, be introduced into Sardinia and Corsica.
Invasive plants determine the loss of local biodiversity and modification of the landscape and their control and management imply important investments of both human and economic resources (
The Apoidea of the Tuscan Archipelago are poorly studied (
Considering the relatively small size of Elba Island and the only recent arrival of M. sculpturalis, the development of an efficient monitoring plan and effective control strategy is still potentially achievable; however, it is important to act promptly before the species can spread over the entire island and the whole archipelago. The monitoring plan, here proposed for Elba Island, can be equally used/repeated on the whole Italian territory, to homogenise the expansion information on M. sculpturalis. To develop an efficient monitoring and containment plan, four factors must be taken into consideration: ease of identification, nesting preferences, phenology and voltinism. Due to its large size and its characteristic appearance, M. sculpturalis can be easily recognised, even by less experienced citizens, as already proven during the data collecting presented in this paper and by
The distribution of M. sculpturalis in the Italian peninsula from 2009 to date demonstrates the great spreading capacity of this species, which was able to colonise the whole country in a few years. An especial concern is given by its presence on Elba Island, which is part of Tuscan Archipelago National Park (PNAT) and represents the tourist and commercial route to Corsica and Sardinia. The particular conditions of vulnerability that occur on island ecosystems could expose them to concrete risks of alteration of their ecological balance by alien species. The observations, made in Europe and the USA, suggest a possible risk for the native flora and fauna due to M. sculpturalis, as a result of competition with local bees for foraging and nesting sites and for the spread of exotic plants. For this reason, we strongly suggest for this species a monitoring and containment action, which should also include an attempt to eradicate it from Elba Island. The results of the Italian monitoring highlight the relevance of Citizen Science contribution, made possible by the large size and the easy recognition of this species. The use of bee hotels, which represent an aggregation site for this species, could work favourably, both for the monitoring and for the control of the species, by destroying the nests at the end of the nesting season.
We thank all our friends and colleagues who kindly provided part of the data used in this paper. Thanks to Benoit Geslin (Institut Méditerranéen de Biodiversité et d’Écologie Marine et Continentale), to Davide Dal Pos (University of Central Florida), to Stephen Johnson (Pella, Iowa) and the two referees for useful suggestion provided during manuscript realisation. The paper was realised with the support of the Tuscan Archipelago National Park (PNAT), as part of the activities funded by "BIONETPARKS – La rete delle aree protette per la tutela degli impollinatori naturali".