Nesting Biology of Megachile (Chrysosarus) jenseni (Hymenoptera: Megachilidae) in Two Contrasting Pampean Agroecosystems: A Potential Pollinator for Alfalfa?

Several crops depend on both managed and wild bees to produce fruits and/or seeds, and the efficiency of numerous wild bees is higher than that of some managed species. Therefore, knowing and understanding the required resources for wild bees could enabled the establishment of management practices to increase their populations. Here, we provide information about the nesting biology of Megachile (Chrysosarus) jenseni, a Faboideae-specialist bee species. Based on observations from two populations occurring in contrasting agroecosystems, this bivoltine species showed common behavioral features shared with other species of subgenus Chrysosarus, such as the use of petal pieces and mud as nesting materials and the utilization of pre-existing cavities. Both studied populations showed a bivoltine life cycle with a rapid early-summer generation and a second generation, with most individuals overwintering. Main causes of mortality were unknown diseases (or other factors), causing the death of preimaginal stages. Moreover, this species was attacked by a cleptoparasite megachilid (Coelioxys remissa), a parasitic eulophid wasp (Melittobia sp.), and a bee fly (Anthrax oedipus). Finally, we discussed the potential use of this leaf-cutter bee species for alfalfa pollination.

New austral-most records of the genus Heterostylum Macquart (Diptera: Bombyiliidae) in Argentina.

Bee flies of the genus Heterostylum Macquart are medium-sized species (1015 mm) characterized primarily by a robust body covered with long pile and by an indented hind margin of the eye (Cunha et al. 2007). There are several studies on the immatures of some species of Heterostylum (Bohart et al. 1960; Yeates Greathead 1997), which are considered ectoparasites of fossorial solitary bee larvae and pupae (Yeates Greathead 1997).

Landscape connectivity explains interaction network patterns at multiple scales.

Under a metacommunity framework, the spatial configuration of habitat fragments could determine local community structure. Yet, quantifying fragment connectivity is challenging, as it depends on multiple variables at several geographical scales. We assessed the extent to which fragment connectivity and area explain patterns in interaction structure among four herbivore guilds and their host plants in a metacommunity. We propose an integrative connectivity metric including geographic distance, neighboring fragment area and similarity in resource composition as an extension of Hanski's classic metric. We then used nonlinear models to assess whether fragment connectivity and area predicted link richness and similarity in link composition. We found that link richness was always negatively related to connectivity but at different geographic scales depending on the herbivore guild. In contrast, while link composition was also related to connectivity, the direction and strength of this relationship varied among herbivore guilds and type of link composition (qualitative or quantitative). Furthermore, focal fragment area was not an important determinant of interaction diversity in local communities. Our findings emphasize resource similarity as a novel dimension of fragment connectivity relevant in explaining interaction diversity patterns in natural trophic networks.