Brood cells of Hoplitis (Anthocopa) dalmatica (Morawitz, 1871) under a turned stone; each brood cell consists of an outer layer of roughly chewed green leaves and an inner layer of petals. Foto A. Müller.

The osmiine bees (Megachilidae, Osmiini), which comprise 15 genera and roughly 1200 species worldwide, occur on all continents except South America, Australia and Antarctica (Michener, 2007; Praz et al., 2008b; Ungricht et al., 2008; but see Gonzalez and Griswold, 2011). They are especially diversified in mediterranean and desertic climates of southern Africa, southwestern North America and the Palaearctic. With 10 genera and about 700 species, the Palaearctic osmiine bee fauna is particularly diverse.

The distribution of the osmiine genera in the six biogeographic regions (after Michener, 2007) is given below with the following abbreviations: Pal=Palaearctic, Nea=Nearctic, Afr=Afrotropic, Ori=Oriental, Neo=Neotropic, Aus=Australian, +=present, (+)=only marginally distributed in this region, -=absent. Recent anthropogenic introductions were not considered.


systematic placement unclear

Ochreriades Pal+/Nea-/Afr+/Ori-/Neo-/Aus-

Bekilia Pal-/Nea-/Afr+/Ori-/Neo-/Aus-

Chelostoma group

Chelostoma Pal+/Nea+/Afr-/Ori(+)/Neo-/Aus-

Heriades group

Heriades Pal+/Nea+/Afr+/Ori+/Neo(+)/Aus-

Hofferia Pal+/Nea-/Afr-/Ori-/Neo-/Aus-

Othinosmia Pal-/Nea-/Afr+/Ori-/Neo-/Aus-

Protosmia Pal+/Nea(+)/Afr-/Ori(+)/Neo-/Aus-

Stenoheriades Pal+/Nea-/Afr+/Ori+/Neo-/Aus-

Xeroheriades Pal-/Nea+/Afr-/Ori-/Neo-/Aus-

Osmia group

Ashmeadiella Pal-/Nea+/Afr-/Ori-/Neo(+)/Aus-

Atoposmia Pal-/Nea+/Afr-/Ori-/Neo-/Aus-

Haetosmia Pal+/Nea-/Afr+/Ori-/Neo-/Aus-

Hoplitis Pal+/Nea+/Afr+/Ori(+)/Neo-/Aus-

Osmia Pal+/Nea+/Afr-/Ori(+)/Neo(+)/Aus-

Wainia Pal+/Nea-/Afr+/Ori(+)/Neo-/Aus-

The results of a recent molecular study (Praz et al., 2008b) indicate a Palaearctic origin of the Osmiini (Figure 1), which is largely supported by the high generic and species diversity observed in the Old World osmiine bees. Only one large clade within the Heriades group, which is comparably diverse in sub-Saharan Africa and the Palaearctic, appears to had an African origin. The phylogeny reveals at least 15 exchanges between the Palaearctic and the Nearctic. For the majority of these exchanges, a colonization of North America from the Palaearctic is assumed. The high percentage of wood or stem nesting taxa among the osmiine bees might explain why the number of exchanges between the Palaearctic and North America is higher than that observed in other groups of bees, which primarily nest in the ground: nesting in wood or in stems facilitate dispersal by overseas transport of the nests.

Figure 1: Maximum likelihood reconstruction of ancestral geographic range for nine selected clades of osmiine bees. Three geographic zones were recognized: Palaearctic (P; white), Nearctic (N; grey) and Afrotropical (A; black). After Praz et al., Molecular Phylogenetics and Evolution, 49, 185-197, 2008.