Early resources lead to persistent benefits for bumble bee colony dynamics

Abstract

Conditions experienced early in development can affect the future performance of individuals and populations. Demographic theories predict persistent population impacts of past resources, but few studies have experimentally tested such carry‐over effects across generations or cohorts. We used bumble bees to test whether resource timing had persistent effects on within‐colony dynamics over sequential cohorts of workers. We simulated a resource pulse for field colonies either early or late in their development and estimated colony growth rates during pulse‐ and non‐pulse periods. During periods when resources were not supplemented, early‐pulse colonies grew faster than late‐pulse colonies; early‐pulse colonies grew larger as a result. These results revealed persistent effects of past resources on current growth and support the importance of transient dynamics in natural ecological systems. Early‐pulse colonies also produced more queen offspring, highlighting the critical nature of resource timing for the population, as well as colony, dynamics of a key pollinator.

Floral resource continuity boosts bumble bee colony performance relative to variable floral resources

“…Such increases in early-season resources are known to elevate colony growth and worker production (Malfi et al, 2021), but the availability of late-season resources may have a more direct impact on drone and gyne production (Rundlöf et al, 2014). This carry-over effect of early-season resource exploitation exhibited by B. impatiens, also seen with B. vosnesenskii (Malfi et al, 2021), may help explain the ability of this species to exploit modern agricultural and human-dominated landscapes in which resources are temporally heterogeneous. Despite total colony mass gain being significantly higher in continuous field colonies relative to pulse-field colonies, the difference in gyne production between them was not statistically evident.…”

“…This was evidenced by the observed increased foraging rates for field colonies near Phacelia. Such increases in early-season resources are known to elevate colony growth and worker production (Malfi et al, 2021), but the availability of late-season resources may have a more direct impact on drone and gyne production (Rundlöf et al, 2014). This carry-over effect of early-season resource exploitation exhibited by B. impatiens, also seen with B. vosnesenskii (Malfi et al, 2021), may help explain the ability of this species to exploit modern agricultural and human-dominated landscapes in which resources are temporally heterogeneous.…”

“…While laboratory studies can provide insights into the mechanisms driving colony responses to variable resource abundance, field experiments are needed to understand how colonies respond under more natural, free-foraging conditions where foraging energy expenditures factor into colony economics. To date, few studies address how variability in resources over time influences colony performance (but see Malfi et al, 2021).…”

“…Because bumble bee colonies are long-lived, the continuous availability of flowers during colony establishment and growth is thought to be critical to colony success (Hemberger et al, 2020;Kevan & Baker, 1983;Schellhorn et al, 2015). For example, worker production in colonies of B. terrestris Linnaeus and B. vosnesenskii Radoszkowski are positively linked to early-season resource availability, suggesting that shortfalls in these resources could negatively impact growing colonies, limiting their ability to produce reproductive individuals (gynes) later in the season (Crone & Williams, 2016;Malfi et al, 2021;Westphal et al, 2009;Williams et al, 2012). Additionally, late-season mass-flowering crops benefit queen production in B. terrestris by eliminating a late-season resource gap (Rundlöf et al, 2014).…”

Experimental heatwaves disrupt bumblebee foraging through direct heat effects and reduced nectar production

“…For many species, minimal food stores may not bridge extended or back-to-back heatwaves resulting in resource shortfalls Malfi et al (2022). Second, bumblebees might adjust daily foraging windows to early and later in the day when temperatures are more aligned to their physiological constraints.…”