Parasitoids of the uniquely social colletid bee Amphylaeus morosus (Hymenoptera: Colletidae) in Victoria

Hearn, Lucas R; Stevens, Mark I.; Schwarz, Michael P.; Parslow, Ben A.

doi:10.24199/j.mmv.2021.80.10

Cited by 2 publications

(1 citation statement)

References 23 publications

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“…Brood cells are laid in a linear sequence, with mothers ovipositing onto semi-liquid provisions before sealing cells (figure 1 b ). In the Dandenong Ranges, Victoria, Australia, A. morosus is attacked by at least eight different parasitoid species with staggered windows of attack driven by host resource utilization [19]. These parasitoids provide severe ecological pressures throughout the reproductive season and have been shown to dramatically increase the benefits of having at least one defender in the nest at the end of the reproductive season [20].…”

Section: Introductionmentioning

confidence: 99%

Extreme reproductive skew at the dawn of sociality is consistent with inclusive fitness theory but problematic for routes to eusociality

2022

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To understand the earliest stages of social evolution, we need to identify species that are undergoing the initial steps into sociality. Amphylaeus morosus is the only unambiguously known social species in the bee family Colletidae and represents an independent origin of sociality within the Apoidea. This allows us to investigate the selective factors promoting the transition from solitary to social nesting. Using genome-wide SNP genotyping, we infer robust pedigree relationships to identify maternity of brood and intracolony relatedness for colonies at the end of the reproductive season. We show that A. morosus forms both matrifilial and full-sibling colonies, both involving complete or almost complete monopolization over reproduction. In social colonies, the reproductive primary was also the primary forager with the secondary female remaining in the nest, presumably as a guard. Social nesting provided significant protection against parasitism and increased brood survivorship in general. We show that secondary females gain large indirect fitness benefits from defensive outcomes, enough to satisfy the conditions of inclusive fitness theory, despite an over-production of males in social colonies. These results suggest an avenue to sociality that involves high relatedness and, very surprisingly, extreme reproductive skew in its earliest stages and raises important questions about the evolutionary steps in pathways to eusociality.

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Section: Introductionmentioning

confidence: 99%

Extreme reproductive skew at the dawn of sociality is consistent with inclusive fitness theory but problematic for routes to eusociality

2022

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Temporal dissonance between group size and its benefits requires whole-of-lifecycle measurements

et al. 2022

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The benefits of living in groups drive the evolution of sociality, and these benefits could vary across a life-cycle. However, there may be experimental problems in linking group size at one time in a life-cycle to benefits that only become apparent later on when group size has changed, leading to what we call “temporal dissonance”. In the only known social colletid bee, Amphylaeus morosus, parasite pressures arise at various times throughout the life-cycle from different parasitoid species. Amphylaeus morosus is impacted by eight different parasitoid species operating at different host-colony phenology phases, including five species of Gasteruption wasps, a bombyliid fly and two mutillid wasp species. We found that, as the reproductive season progressed, the number of host adults in a nest declined, often to zero, but the presence of even one adult host female during late brood-rearing stages appeared to offer substantial brood protection against mutillids. We propose that the apparent benefits of colony size at one point in time may not reflect the benefits that become apparent at a later point in the season, leading to a temporal dissonance between group size and its later fitness benefits. We also show that A. morosus is strongly protogynous, with variation in parasitoid pressure across the reproductive phenology distorting operational sex ratios away from initial investment ratios. Combined, our data suggest that seasonal variation in parasitoid pressure may have major consequences for understanding social evolution, but these kinds of consequences are largely unexplored in current studies of insect social evolution.

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Parasitoids of the uniquely social colletid bee Amphylaeus morosus (Hymenoptera: Colletidae) in Victoria

Cited by 2 publications

References 23 publications

Extreme reproductive skew at the dawn of sociality is consistent with inclusive fitness theory but problematic for routes to eusociality

Extreme reproductive skew at the dawn of sociality is consistent with inclusive fitness theory but problematic for routes to eusociality

Temporal dissonance between group size and its benefits requires whole-of-lifecycle measurements

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