Abstract
Foraging specialization allows social insects to more efficiently exploit resources in their environment. Recent research on honeybees suggests that specialization on pollen or nectar among foragers is linked to reproductive physiology and sensory tuning (the Reproductive Ground-Plan Hypothesis; RGPH). However, our understanding of the underlying physiological relationships in non-Apis bees is still limited. Here we show that the bumblebee Bombus terrestris has specialist pollen and nectar foragers, and test whether foraging specialization in B. terrestris is linked to reproductive physiology, measured as ovarian activation. We show that neither ovary size, sensory sensitivity, measured through proboscis extension response (PER), or whole-body lipid stores differed between pollen foragers, nectar foragers, or generalist foragers. Body size also did not differ between any of these three forager groups. Non-foragers had significantly larger ovaries than foragers. This suggests that potentially reproductive individuals avoid foraging.
Highlights
Eusociality is characterized by the division of colonies into a reproductive queen and nonreproductive workers
The reproductive groundplan hypothesis (RGPH) proposes a mechanism for the evolution of pollen/nectar foraging preference in bees in which reproductive physiology is linked to foraging specialization (Amdam et al, 2004; Amdam et al, 2006; Page et al, 2006; Page, Rueppell & Amdam, 2012; Page & Amdam, 2007; Roth et al, 2014)
We quantitatively demonstrate pollen and nectar specialization among B. terrestris foragers for the first time
Summary
Eusociality is characterized by the division of colonies into a reproductive queen and nonreproductive workers. There may be further task specialization, especially in large-colony species with derived social organization. Understanding the mechanisms underlying such specialization can suggest how worker task specialization and its attendant social coordination evolved. The reproductive groundplan hypothesis (RGPH) proposes a mechanism for the evolution of pollen/nectar foraging preference in bees in which reproductive physiology is linked to foraging specialization (Amdam et al, 2004; Amdam et al, 2006; Page et al, 2006; Page, Rueppell & Amdam, 2012; Page & Amdam, 2007; Roth et al, 2014). Studies of honeybees show that individual pollen foraging specialists have more developed ovaries with more ovarioles than nectar foragers
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