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Abstract Egg rejection is an effective and widespread antiparasitic defense to eliminate foreign eggs from the nests of hosts of brood parasitic birds. Several lines of observational and critical experimental evidence support a role for learning by hosts in the recognition of parasitic versus own eggs; specifically, individual hosts that have had prior or current experience with brood parasitism are more likely to reject foreign eggs. Here we confirm experimentally the role of prior experience in altering subsequent egg-rejection decisions in the American robin Turdus migratorius, a free-living host species of an obligate brood parasite, the brown-headed cowbird Molothrus ater. We then model the coevolutionary trajectory of both the extent of mimicry of host eggs by parasitic eggs and the host’s egg rejection thresholds in response to an increasing role of learning in egg recognition. Critically, with more learning, we see the evolution of both narrower (more discriminating) rejection thresholds in hosts and greater egg mimicry in parasites. Increasing host clutch size (number of eggs/nest) and increasing parasite load (parasitism rate) also have narrowing effects on the egg-rejection threshold. Together, these results suggest that learning from prior experience with egg rejection may play an important role in the coevolution of egg-mimetic lineages of brood parasites and the refined egg rejection defenses of hosts.
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Host-parasite interactions between Xenoglossa pruinosa (Apidae: Eucerini) and Triepeolus remigatus (Apidae: Epeolini) are characterized by tolerance and avoidance
Abstract In cleptoparasitic bees, host aggression and detection avoidance might be the main selective pressures shaping host-parasite interactions. However, the behavioral responses toward parasitism are unknown for most host species. In this study, we investigated the host-parasite interactions and behaviors of the cleptoparasitic beeTriepeolus remigatuswhen parasitizing the nests of its host, the squash beeXenoglossa(Peponapis)pruinosa. Using circle-tube behavioral assays and direct observations at a nest aggregation ofX. pruinosa, we assessed whether interactions between host and parasite were aggressive, tolerant, or avoidant and characterized the general parasitic behavior ofT. remigatus. Our results reveal a lack of aggression between host and cuckoo bees, with interactions primarily characterized by tolerant and avoidant behaviors. Squash bees displayed minimal aggression toward both conspecifics and parasites. Interestingly, despite the absence of aggressive responses,T. remigatuspreferred entering nests while the host was foraging, potentially indicating a strategy to avoid the discovery of parasitic visits. Furthermore, field observations provided insights into the parasitic behavior ofT. remigatus, revealing primarily rapid visits to host nests without extensive inspection. The limited aggression and short time for nest visits observed inT. remigatussuggest adaptations to optimize parasitic success while minimizing host detection. Overall, our findings contribute to a better understanding of the behavior of open-cell parasites and provide a first accounting of the squash bee behavior when encountering parasitic bees. Further research is needed to elucidate the mechanisms underlying host-parasite coevolution and response to parasitism in ground-nesting bees.
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- Award ID(s):
- 2046474
- PAR ID:
- 10556910
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Apidologie
- Volume:
- 55
- Issue:
- 6
- ISSN:
- 0044-8435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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