Emergence Phenology ofOsmia lignariasubsp.lignaria(Hymenoptera: Megachilidae), Its ParasitoidChrysura kyrae(Hymenoptera: Chrysididae), and Bloom ofCercis canadensis

Abstract

Emergence patterns of a natural population of Osmia lignaria subsp. lignaria Say were monitored during a 5-yr period (2003-2007) in relation to air temperature, bloom of eastern redbud (Cercis canadensis L.), and emergence of the parasitoid Chysura kyrae Krombein. Bee cocoons were placed in gelatin capsules and overwintered within shelters in their natural habitat. Mean emergence of female O. l. lignaria was observed at approximately 2 d after redbud bloom began; mean male emergence was approximately 1 wk earlier than for females and was nearly identical to that of C. kyrae. Horticultural models used to predict budburst for several tree species were evaluated with respect to redbud bloom and O. l. lignaria emergence. Each model indicated that both sexes of the bee and redbud had similar chill unit requirements. Differences in emergence and bloom dates were attributed to the different requirements for growing degree hours (GDHs) after chilling requirements were met. The close phenological relationship observed between eastern redbud and bee emergence suggests an important role for this common understory tree in the early nesting success of O. l. lignaria.

Habitat fragmentation influences genetic diversity and differentiation: Fine‐scale population structure of Cercis canadensis (eastern redbud)

“…Eastern redbud is similar to many other self‐incompatible species (Roberts et al, 2015), wherein C. canadensis depends on insect‐, mammal‐, and bird‐mediated pollination for dispersal. In its natural distribution pollinators of C. canadensis include honeybees, megachilid bees, small sweat bees, butterflies, and beetles (Dickson, 1990; Kraemer & Favi, 2010; Tucker, 2002). These insects are usually capable of flying one to several kilometers, depending on the insect species and environmental conditions, so pollen‐based gene flow was expected to be high across fine‐scale geographical ranges (Hagler, Mueller, Teuber, Machtley, & Deynze, 2011; Kramer et al, 2008; Pasquet et al, 2008).…”

Plant–pollinator interactions and phenological change: what can we learn about climate impacts from experiments and observations?

“…Studies evaluating which variables predict seasonal timing of flowering and insect pollinator emergence often find that temperatures are good predictors of both plant and pollinator phenology, at least in temperate and Mediterranean regions (Hegland et al , Gordo and Sanz , Doi et al , Forrest and Thomson ). Both warm temperatures in spring and cold temperatures in winter seem to be important for temperate‐region plants and insects (Bosch and Kemp , Kraemer and Favi , Tooke and Battey , Forrest and Thomson , Laube et al ), although the details of how temperature affects plants and insects may differ. Timing of snowmelt is highly correlated with flowering time and activity periods of many plants and some flower‐visiting animals (Inouye et al , Green , Lambert et al , Iler et al , Kudo and Ida ); however, the apparent effect of snowmelt on phenology may be indirect, driven by its effect on soil temperatures – for which long‐term data are unavailable.…”

Nesting and Pollen Preference ofOsmia lignaria lignaria(Hymenoptera: Megachilidae) in Virginia and North Carolina Orchards

“…Orchards are usually in bloom for relatively short periods of time even when a variety of fruit trees are present. In the mid-Atlantic region, natural emergence of female O. lignaria is coincident with initial bloom of eastern redbud and usually several days to a week before apple bloom (Kraemer and Favi 2010). Nest building activity begins a few days after emergence (Bosch and Kemp 2001) and extends for at least several weeks after apple petal drop, until early to mid-May in this study.…”

“…The prevalence of redbud pollen in nest provisions from multiple orchards and the coincidence of female emergence with redbud bloom (Kraemer and Favi 2010) suggest that these two native species have an important ecological relationship in eastern hardwood forests. They share a common range from Massachu- (Little 1977, Krombein 1979, USDAÐNRCS 2013.…”