Where and why? Bees, snail shells and climate: Distribution of Rhodanthidium (Hymenoptera: Megachilidae) in the Iberian Peninsula

Abstract

Species distribution patterns are widely studied through species distribution models (SDMs), focusing mostly on climatic variables. Joint species distribution models (JSDMs) allow inferring if other factors (biotic interactions, shared phylogenetic history or other unmeasured variables) can also have an influence on species distribution. We identified current distributional areas and optimal suitability areas of three species of the solitary snail‐shell bee Rhodanthidium (Hymenoptera: Megachilidae), and their host gastropod species in the Iberian Peninsula. We undertook SDMs using Maxent software, based on presence points and climatic variables. We also undertook JSDMs for the bees and the snails to infer if co‐occurrence could be a result of biotic interactions. We found that the three bee species: (1) use at least five different species of Mediterranean snails; (2) use empty shells not only for nesting but also for sheltering when there is adverse weather and during the night; (3) have their most suitable areas in the eastern and southern Iberian Peninsula, mostly on limestone areas; and (4) have their optimal range under Mediterranean climatic values for the studied variables. There is positive co‐occurrence of Rhodanthidium with the gastropod species, especially with the snail Sphincterochila candidissima. The contribution of the environmental component to the co‐occurrence is less than that of the residual component in those cases, suggesting that: (i) the use of biotic resources (between Rhodanthidium and the gastropod species); (ii) shared phylogenetic history (between R. septemdentatum and R. sticticum); or (iii) unmeasured variables are largely responsible for co‐occurrence.

Comparative biology of four Rhodanthidium species (Hymenoptera, Megachilidae) that nest in snail shells

“…Additional studies are needed, especially for the species R. infuscatum, which is the rarest of the four species studied (Kasparek 2019). R. sticticum and R. septemdentatum are common species that form large local populations in southern Europe (Torné-Noguera et al 2014;Romero et al 2020) and the latter occurs in steppe habitats of conservation interest in central Europe (Bogusch et al 2019(Bogusch et al , 2020.…”

“…The tribe Anthidiini displays a wide variety of nesting behaviours, including nesting underground, using various types of cavities and building exposed nests (Michener 2007;Litman et al 2016;Westrich 2018). Nesting in shells in this tribe has been recorded in only four Palaearctic species of Rhodanthidium (Erbar and Leins 2017;Baldock et al 2018;Westrich 2018;Romero et al 2020) and two Afrotropical species of Afranthidium Gess 2008, 2014).…”

“…infuscatum: Pasteels 1977;R. sticticum: Schremmer 1960;Pasteels 1977;Ortiz-Sánchez 1990;Bosch et al 1993;Romero et al 2020), a comprehensive study of their biology has not yet been published. In particular, the range of snail species used by these species is unknown; the only relevant publication to date is that of Romero et al (2020), who studied the use of empty gastropod shells by adults during inclement weather and at night.…”

Algunos rasgos de la biología de la abeja roja de los caracoles, Rhodanthidium sticticum (Fabricius, 1787): fenología, preferencia floral, uso de conchas, capacidad de vuelo y comportamiento territorial

“…The red snail shell nesting bee, Rhodanthidium sticticum (Fabricius, 1787) (Hymenoptera, Megachilidae), is a Mediterranean solitary bee species (Ornosa et al, 2008), best known for its striking red colour and its nesting behaviour, inside empty snail shells, used for sheltering, too (Romero et al, 2020a). The use of Gastropod shells by bees has mostly been described for nesting, but very rarely for sheltering, and it is exclusive from the family Megachilidae (Pasteels, 1977;Gess & Gess, 1999Moreno-Rueda et al, 2008, Müller et al, 2018Kuhlmann et al, 2011;Müller & Mauss, 2016).…”

“…Besides R. sticticum, three more species of Rhodanthidium (R. infuscatum (Erichson, 1835), R. septemdentatum (Latreille, 1809) and R. siculum (Spinola, 1838)) build their nests inside snail shells (Dusmet, 1908;Pasteels, 1977;Erbar & Leins, 2017). As they are obliged shell-nesters (Bosch et al, 1993), the presence of empty shells and the distribution of the appropriate Gastropod species influence the distribution of the Rhodanthidium bees themselves (Romero et al, 2020a), and the retraction or expansion of the snails range affects that of the snail-nesting Rhodanthidium species (Bogusch et al, 2020) Another particular feature of R. sticticum is its territorial behaviour. The defence of an attractive territory to get access to females is known as "resource defence polygyny" (Emlen & Oring, 1977) and it has been widely described in Anthidiini: Anthidiellum notatum (Latreille, 1809) (Turell, 1976), A. perplexum (Smith, 1854) (Turell, 1976), Anthidium banningense Cockerell, 1904(Jaycox, 1967), A. florentinum (Fabricius, 1775 (Batra, 1978;Wirtz et al, 1992;García-González & Ornosa, 1999), Anthidium illustre Cresson, 1879 (Alcock, 1977), A. maculosum Cresson, 1878 (Alcock et al, 1977), A. manicatum (Linnaeus, 1758) (Severinghaus et al, 1981;Wirtz et al, 1988Wirtz et al, , 1992Payne et al, 2011), A. palliventre Cresson, 1878 (Villalobos & Shelly, 1991), A. palmarum Cockerell, 1904(Wainwright, 1978, A. porterae Cockerell, 1900(Villalobos & Shelly, 1991, A. septemspinosum Lepeletier, 1841 (Sugiura, 1991), R. septemdentatum the end of May (85% of the records, Fig.…”