Stelis (Stelis) odontopyga (Noskiewicz, 1925)

Stelis (Stelis) odontopyga (Noskiewicz, 1925) View in CoL

Figs 8 View Fig , 13 C View Fig

SHORT DESCRIPTION: A very small (6-7 mm) Stelis species that lacks any light maculations and bands of hairs on the terga. Can be found in locations where its host is common, hovering close to the ground and scanning snail shells.

HOST SPECIES: Osmia spinulosa (Kirby, 1802) ( KASPAREK, 2015; WESTRICH, 2018)

DISTRIBUTION IN EUROPE: Europe from Spain to Russia, south to Turkey. Northwards to the Grand Duchy of Luxembourg ( HERRERA MESÍAS & WEIGAND, 2021), Germany, Poland and Czech Republic ( SCHEUCHL & WILLNER, 2016). There are no records from the Netherlands ( REEMER, 2018; www.waarneming.nl), nor from the United Kingdom ( ELSE & EDWARDS, 2018), but it is present in France ( KASPAREK, 2015).

EU RED LIST STATUS: Least concern (LC) ( NIETO et al., 2014)

ORIGIN OF RECORDS:

- WEST FLANDERS PROVINCE. Koksijde ; 1♂; 6.vii.2007; leg./coll./det. J. Devalez. 1♂; 30.vii.2007; leg./coll./det. J. Devalez. 1♂; 4.vi.2011; leg. J. D’Haeseleer; coll. AHHAA Science centre Tartu ( Estland); det. J. D’Haeseleer, J. Devalez. 3♀♀; 22.vii.2019; leg./ coll./det. J. D’Haeseleer; 1♀; 29.vii.2019; leg. K. Geeraerts; det. J. D’Haeseleer; - Fig. 13 C View Fig . 1 View Fig ♀; 27.vi.2023; leg./det. M. Wielandts. 1♀; 6.vii.2023; leg./det. M. Wielandts. 2♀♀; 12.vii.2023; leg./det. M. Wielandts. 2♂♂; 13.vii.2023; leg./det. M. Wielandts. 1♀; 26.vii.2023; leg./det. M. Wielandts. De Panne ; 1♂; 18.vi.2019; leg./coll./det. J. D’Haeseleer. 2♂♂; 22.vii.2019; leg./coll./det. W. Proesmans. 1♂; 8.vii.2023; leg./coll./ det. Y. Gevaert. Brugge; 1♂; 16.vi.2020; leg./coll./det. W. Tamsyn, J. Devalez. 1♂ 18.vii.2023; leg./ det. M. Wielandts. Oostende; 1♂; 13.vii.2020; leg./coll. F. Verheyde; det. F. Verheyde, T. de Blanck. 1♀; 27.vii.2022; leg./coll./det. D. De Grave. 1♂ 1♀; 20.vii.2023; leg./det. M. Wielandts. 1♂ 2♀♀; 26.vi.2023; leg./coll./det. M. Wielandts. De Haan ; 1♂; 23.vi.2022; leg./coll./det. M. Wielandts. 1♀; 27.vii.2022; leg./coll./det. M. Wielandts. Bredene; 1♀; 12.vii.2022; leg./det./coll. T. De Blanck. Middelkerke ; 1♀; 3.vii.2023; leg./det. M. Wielandts.

- HAINAUT PROVINCE. Boussu; 1♂; 3.vii.2019; leg./coll./det. T. J. Wood. 1♀; 20.vi.2020; leg./coll./det. T. J. Wood .

- ANTWERP PROVINCE. Antwerpen; 1♂; 3.vi.2020; leg./coll./det. W. Vertommen.

COMMENTS:

- The species is most likely expanding, following its host species, and was recently recorded as new for Britain ( EDWARDS et al., 2019). It was also found in northern France in 2017 ( LEMOINE et al., 2020) and Südniedersachsen in 2020 ( FECHTLER et al., 2021).

Discussion

This study brings additional knowledge on the Belgian bee fauna since the IUCN Belgian Red List of bees that was published in 2019 ( DROSSART et al., 2019). A total of 24 wild bee species have been recorded as new for the country since then. 11 other species that were thought to be extinct previously, and reported as such by DROSSART et al. (2019), have now been rediscovered. And lastly, we provide additional records for six species previously only recorded once in Belgium. Collectively, and together with the fact that T. J. Wood has recently eliminated eight Andrena species from the Belgian checklist (namely Andrena barbareae (Panzer, 1805) , A. chrysopus (Pérez, 1902) , A. cinerea (Brullé, 1832) , A. decipiens (Schenck, 1861) , A. distinguenda (Schenck, 1861) , A. nanula (Nylander, 1848) , A. nitidula (Pérez, 1903) and A. spreta Pérez, 1895 ) ( WOOD, 2023), these results increase the total number of wild bee species that have been recorded in Belgium so far to 419 species, including 386 species with recent/contemporary (i.e., post-2000) occurrence records.

Overall, our study highlights the importance of targeted field surveys to adequately monitor the presence of wild bee species. Here, we combined forces of citizen sciences and academic surveys to enhance and improve our understanding of the distribution and persistence of rare species or those that have low detection rates. Typically, when DROSSART et al. (2019) assessed the IUCN Red List categories for wild bees in Belgium, several species that had been observed more than once before 1990 and not anymore afterwards, were considered to be extinct. However, Belgium has experienced a period of decreased records between 1990 and 2010, with very few taxonomists and para-taxonomists actively inventorying wild bees anywhere in the country. The situation changed after 2010, notably driven by the creation of the working group Aculea and their intensive training schemes, and indirectly the increased number of qualitative observations posted on citizen-science portals like waarnemingen.be/observations.be, but also the research carried out at Natuurpunt Studie and universities like ULB and UMons. This new dynamic in data acquisition and data sharing has fuelled the present study and allowed us to rediscover several species that were thought to be extinct, like Aglaopis tridentata , Stelis minima and all the other species in their category described above. The current dense network of experienced bee observers makes it increasingly likely that species that are (still) highly localised or extremely rare are discovered. Judged by the presence of recent observations at different years and localities, at least 26 out of 41 of these species currently have established populations in the country. We expect this to be the case for most of the remaining 15 species as well however, especially the species that are difficult to find or identify. Alternatively, it concerns vagrant individuals or temporary small populations. Targeted inventories should be conducted to clarify their status in Belgium. We reckon this is still the beginning of a new era, and we call for coordinated, increased and improved surveys in several of the hitherto undersampled regions of Wallonia and Flanders. This should be a priority target for financial support during the ongoing National Pollinator Strategy (2021-2030) in order to maintain a high data coverage throughout the country, reduce the percentage of species with an unknown status, and produce more scientifically-informed trend analyses within and beyond the timeframe of a future revision of the IUCN Red List of Bees.

There are several mutually non-exclusive reasons why precisely the here reported species were (for a long time) not recorded in Belgium (before). Some were until recently not recorded or recognised due to taxonomic issues. These include Andrena afzeliella , A. confinis and Nomada glabella . The first species was only recognised recently, the other two were until recently not recognised as separate species. Both Andrena species were discovered by T.J. Wood, when he checked the collections at RBINS, ULB and the collections of para-taxonomists from the working group Aculea. Other species were probably elusive due to their very rare or localised occurrence, sometimes in combination with the fact that they are difficult to identify. The first may be the case for many of the cuckoo bees reported here, most of which are dependent on rare host species, like Nomada atroscutellaris , N. braunsiana , N. errans or Stelis odontopyga . Small Lasioglossum species like L. intermedium , L. limbellum and L. puncticolle or Hylaeus kahri for example combine both reasons for being elusive. Andrena fulvata , for which none of us previously had enough experience to reliably separate it from resembling species, has now been checked by taxonomist and co-author T. J. Wood. Finally, species may also have increased its distribution and abundance, often (re)colonising the country in recent years. Andrena lagopus , A. rufula , Anthidium septemspinosum , Ceratina chalybea , Halictus langobardicus , Heriades rubicola , Hylaeus kahri , Megachile nigriventris , Pseudoanthidium nanum , Halictus subauratus and possibly also Stelis odontopyga seem to be rapidly claiming new areas, shown by the entirely different locations on which we have found them within the short timespan between the first and the most recent observation. Most of these species have also recently been discovered in neighbouring regions in the Netherlands, the Grand Duchy of Luxembourg, and some even in the United Kingdom. It typically concerns thermophilic, mobile species and they have been found mostly in warm and sunny locations.

While awaiting further analysis, we reckon that we are increasingly witnessing the impact of climate change on the distribution and phenology of wild bee species in Belgium. It is arguably challenging to predict ectotherm responses to climate change (see e.g. WILSON et al., 2007; SINCLAIR et al., 2016), and likely premature to identify climate change as a key driver behind the new records related to wild bee species that have so far only been seen in a limited number of locations. Yet, we speculate that climate change is likely to impact their distribution by triggering a northward shift in the years to come, which would increase their presence and likelihood to be recorded in Belgium and even our neighbouring countries in the North. By contrast, we highlight that the nine so-called “Climate change species” are opportunistic species that are well capable of colonizing new locations under climate change-induced shifts in their habitat/environmental suitability regions. These species are already well known and common in other regions of Europe where they are - by and large - considered as being of “Least Concern” ( NIETO et al., 2014), pollen generalists or pollen specialists on widespread host plants (e.g. for Andrena lagopus on weedy or cultivated Brassicaceae , or Heriades rubicola on a wide range of Asteraceae ). This phenomenon is also echoed in the contemporary literature on observed and/ or modeled shifts of geographical ranges under global change scenarios ( MUSOLIN & SAULICH 2012; on bees see e.g. RASMONT et al., 2015; MARSHALL et al., 2017, 2020), including on phenological shifts observed in Belgium and neighbouring countries ( JACOBI & KOSLOWSKI, 2023).