Solitary bees (Hymenoptera, Apoidea) as connectors in pollination networks: the case of Rhodanthidium Daniel Romero, Concepción Ornosa, Pablo Vargas, Jens M. Olesen To cite this version: Daniel Romero, Concepción Ornosa, Pablo Vargas, Jens M. Olesen. Solitary bees (Hymenoptera, Apoidea) as connectors in pollination networks: the case of Rhodanthidium. Apidologie, 2020, 51 (5), pp.844-854. 10.1007/s13592-020-00765-2. hal-03207621 HAL Id: hal-03207621 https://hal.archives-ouvertes.fr/hal-03207621 Submitted on 26 Apr 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Apidologie (2020) 51:844–854 Original article * INRAE, DIB and Springer-Verlag France SAS, part of Springer Nature, 2020 DOI: 10.1007/s13592-020-00765-2 Solitary bees (Hymenoptera, Apoidea) as connectors in pollination networks: the case of Rhodanthidium 1 1 2 3 Daniel ROMERO , Concepción ORNOSA , Pablo VARGAS , Jens M. OLESEN 1Department of Biodiversity, Ecology and Evolution; Faculty of Biological Sciences, University Complutense of Madrid, José Antonio Nováis Street, 12, Ciudad Universitaria, 28040, Madrid, Spain 2Real Jardín Botánico, CSIC, Madrid, Spain 3Department of Bioscience, Aarhus University, Aarhus, Denmark Received 16 September 2019 – Revised 14 February 2020 – Accepted 30 March 2020 Abstract – Bees (Apoidea) are the main pollinator group in Mediterranean ecosystems, having a dominant role as connectors of modules (groups of species tightly linked in pollination networks), but little is known about the role of particular species. Here, we analyse data from four Iberian networks, and we pay special attention to the role played by the solitary snail-shell bee Rhodanthidium sticticum (Fabricius, 1787) in shaping network modularity. Our results show that R . sticticum is a pollination generalist that acts as an important connector of modules, strongly influencing the topology of its networks. We also examined 51 networks from all over the world to determine the modular role of other Anthidiini species. Anthidiini were present in 14 of these networks and another Rhodanthidium species, but also two Anthidium species, played a role as connectors in their respective networks. connector / pollination network / Rhodanthidium / solitary bees 1. INTRODUCTION Mello et al. (2013), Tucker and Rehan (2016), Gresty et al. (2018) and Jauker et al. (2019). Thus, Within an ecological space, plant-flower visitor by now, we know that bees are commonplace in mutualistic interactions combine into pollination pollination networks and that they connect differ- networks (Delmas et al. 2019, Herrera 2019). ent modules, i.e. tightly linked network groups Pollination network studies may encompass all (Olesen et al. 2007), but the ecological role of pollinator species within a given study area and particular species for network topology remains period (‘total pollination networks’) or slice out uncertain. This information could be very valu- certain groups of special interest, e.g. birds able for the development of network conservation (Rodríguez-Rodríguez and Valido 2008, Traveset plans, in particular those which focus upon eco- et al. 2015). system functionality. Here, we focus upon the bees. Their network In general, there is plenty of knowledge on the role, as a group, has recently been addressed in relationship between phenotypic traits and topo- logical roles, as species morphology frequently Electronic supplementary material The online version of modulates network structure by both facilitating this article (https://doi.org/10.1007/s13592-020-00765-2) and hindering possible interactions (Olesen et al. contains supplementary material, which is available to 2010,Ibáñez2012). That is the case for birds’ authorized users. bills size and flower size (Biddick and Burns Corresponding author: D. Romero, 2018), bees’ proboscides length and flowers’ spur [email protected] length (Blanco-Pastor et al. 2015) and oil flowers Manuscript editor: Alexandra Klein and long-legged bees (Pauw et al. 2017). Role of solitary bees in pollination networks 845 However, not so much is known about the impor- et al. 2015). Rhodanthidium sticticum may then tance to networks of taxa with special biology, play both an ecological and evolutionary role to such as solitary and territorial bees or bees with Antirrhinum species, but its functional role in specific nesting requirements. The ecological role entire communities in which snapdragons are of particular species in networks has only recently partners remains unknown, although we expect been addressed (Olesen et al. 2018) and it is bees in general and R . sticticum in particular to unknown for most published networks and the be relevant connectors between network modules; species involved. The latter step is important be- we do so, because they visit a highly diverse cause it bridges the gap between ecological net- group of plants. Eighty-five percent of all plant work theory and the ecology of individual species. and pollinator species in pollination networks are As an example, we here analyse in detail the of peripheral importance, i.e. they only interact ecology and network roles played by with one or few other species (Olesen et al. 2007). Rhodanthidium sticticum (Fabricius, 1787) (Fig- However, the last 15% are structurally impor- ure 1), a solitary bee distributed across the western tant. They are either hubs, i.e. highly linked spe- Mediterranean (Ornosa et al. 2008). It belongs to cies within their own module, connectors linking the tribe Anthidiini, which is widespread in the different modules, or both. If any of these key world in terms of its genera. Its species are solitary species go extinct, modules and networks may and territorial (Michener 2007). However, the disintegrate and trigger cascades of local extinc- more detailed ecology is poorly studied, e.g. tion (Memmott et al. 2004, Kaiser-Bunbury et al. nesting, territorial behaviour and pollination ecol- 2010). Thus, hubs and connectors should receive ogy (Torres et al. 2001, Torné-Noguera et al. conservation priority. Our present hypothesis is 2014). Rhodanthidium sticticum appears to be that R . sticticum plays an essential structuring one of the most abundant species and a major role in Mediterranean pollination networks in pollinator in some Mediterranean plant communi- which Antirrhinum species are members. By es- ties (Torné-Noguera et al. 2014), being essential sential role, we mean that it connects network for some threatened and endemic species (Blanco- modules and contributes to the structure and thus Pastor et al. 2015,Vargasetal.2017). It is active stability of the networks. Our objectives become during the entire flowering season (from the be- (i) to analyse different plant communities where ginning of March to the end of June). Low pollen the interaction Rhodanthidium-Antirrhinum oc- specialisation has been recorded for R . sticticum , curs; (ii) to determine the specific network role and thus it is considered polylectic, i.e. it collects of R . sticticum in these communities; and (iii) to pollen from many unrelated plant families, at least analyse the role of other Anthidiini species and, in parts of its range (Torné-Noguera et al. 2014). especially other Rhodanthidium species. In a study of 18 Iberian plant species (Vargas et al. 2017), this bee species was the main polli- 2. MATERIAL AND METHODS nator of five snapdragons or Antirrhinum species (A . barrelieri , A . charidemi , A . hispanicum , A . 2.1. Study sites and interaction sampling molle and A . microphyllum ) and a dominant pollinator of three other snapdragons (A . aus- Previously, we have observed the interaction trale , A . mollissimum and A . pulverulentum ), between Rhodanthidium and Antirrhinum in playing a key role to the survival of these species, eight communities in the Iberian Peninsula of which some are threatened. Indeed, the polli- (Vargas et al. 2017); four of these were selected nation effectiveness of R . sticticum clearly and field surveys were performed. By choosing favoured the reproductive success of these these four locations, we obtained a range in level Antirrhineae species (Vargas et al. 2010). Conse- of visitation frequency performed by R . sticticum quently, R . sticticum could also be a selection to different Antirrhinum species. The Antirrhi- factor in snapdragon evolution, as it is the case num species were A . molle (Huesca, Gabasa; for the occluded corolla evolution of several spe- 42.007153°, 0.416735°) and A . microphyllum cies of the closely related Linaria (Blanco-Pastor (Guadalajara, Buendía; 40.394967°, − 846 D. Romero et al. Figure 1. Female (left and right) and male (centre) of Rhodanthidium sticticum . 2.791320°), both with R . sticticum as their main number of observed interactions (I ); and pollinator (> 50% of visits), A . mollissimum connectance (C =I/AP ). Other parameters were (Almería, Enix; 36.877929°, − 2.609264°) with calculated, and are included in Appendix 4. R . sticticum as its predominant pollinator (> Connectance is the ratio between the number of 25% of visits),