TY - JOUR
T1 - Host responses to interspecific brood parasitism
T2 - A by-product of adaptations to conspecific parasitism?
AU - Samas, Peter
AU - Hauber, Mark E.
AU - Cassey, Phillip
AU - Grim, Tomas
N1 - Funding Information:
We are grateful to Z. Šebestová for creating the egg models and to A. Dvorská, L. Polačiková, Z. Strachoňová and L. Turčoková for field assistance. The study was supported by the Human Frontier Science Program RGY69/ 2007 (to TG, PC & MEH) and RGY83/2012 (to MEH & TG), MSM6198959212 grant (to TG), the PCS-CUNY grant program (to MEH), and the Leverhulme Trust (to PC & MEH). For assistance we are grateful to the Auckland Regional Council, Auckland Botanic Gardens, M. Anderson, the University of Waikato, and landowners allowing us to use their property. For discussions and comments on the manuscript we are grateful to the late A. Antonov, and to Z. Aidala, M. Anderson, J. Avilés, R. Boulton, J. Briskie, B. Croston, N. Davies, M.
PY - 2014/4/28
Y1 - 2014/4/28
N2 - Background: Why have birds evolved the ability to reject eggs? Typically, foreign egg discrimination is interpreted as evidence that interspecific brood parasitism (IP) has selected for the host's ability to recognize and eliminate foreign eggs. Fewer studies explore the alternative hypothesis that rejection of interspecific eggs is a by-product of host defenses, evolved against conspecific parasitism (CP). We performed a large scale study with replication across taxa (two congeneric Turdus thrushes), space (populations), time (breeding seasons), and treatments (three types of experimental eggs), using a consistent design of egg rejection experiments (n = 1057 nests; including controls), in areas with potential IP either present (Europe; native populations) or absent (New Zealand; introduced populations). These comparisons benefited from the known length of allopatry (one and a half centuries), with no gene flow between native and introduced populations, which is rarely available in host-parasite systems.Results: Hosts rejected CP at unusually high rates for passerines (up to 60%). CP rejection rates were higher in populations with higher conspecific breeding densities and no risks of IP, supporting the CP hypothesis. IP rejection rates did not covary geographically with IP risk, contradicting the IP hypothesis. High egg rejection rates were maintained in the relatively long-term isolation from IP despite non-trivial rejection costs and errors.Conclusions: These egg rejection patterns, combined with recent findings that these thrushes are currently unsuitable hosts of the obligate parasitic common cuckoo (Cuculus canorus), are in agreement with the hypothesis that the rejection of IP is a by-product of fine-tuned egg discrimination evolved due to CP. Our study highlights the importance of considering both IP and CP simultaneously as potential drivers in the evolution of egg discrimination, and illustrates how populations introduced to novel ecological contexts can provide critical insights into brood parasite-host coevolution.
AB - Background: Why have birds evolved the ability to reject eggs? Typically, foreign egg discrimination is interpreted as evidence that interspecific brood parasitism (IP) has selected for the host's ability to recognize and eliminate foreign eggs. Fewer studies explore the alternative hypothesis that rejection of interspecific eggs is a by-product of host defenses, evolved against conspecific parasitism (CP). We performed a large scale study with replication across taxa (two congeneric Turdus thrushes), space (populations), time (breeding seasons), and treatments (three types of experimental eggs), using a consistent design of egg rejection experiments (n = 1057 nests; including controls), in areas with potential IP either present (Europe; native populations) or absent (New Zealand; introduced populations). These comparisons benefited from the known length of allopatry (one and a half centuries), with no gene flow between native and introduced populations, which is rarely available in host-parasite systems.Results: Hosts rejected CP at unusually high rates for passerines (up to 60%). CP rejection rates were higher in populations with higher conspecific breeding densities and no risks of IP, supporting the CP hypothesis. IP rejection rates did not covary geographically with IP risk, contradicting the IP hypothesis. High egg rejection rates were maintained in the relatively long-term isolation from IP despite non-trivial rejection costs and errors.Conclusions: These egg rejection patterns, combined with recent findings that these thrushes are currently unsuitable hosts of the obligate parasitic common cuckoo (Cuculus canorus), are in agreement with the hypothesis that the rejection of IP is a by-product of fine-tuned egg discrimination evolved due to CP. Our study highlights the importance of considering both IP and CP simultaneously as potential drivers in the evolution of egg discrimination, and illustrates how populations introduced to novel ecological contexts can provide critical insights into brood parasite-host coevolution.
KW - Coevolution
KW - Collateral damage
KW - Discrimination
KW - Heterospecific brood parasitism
KW - Intraspecific brood parasitism
KW - Species introductions
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U2 - 10.1186/1742-9994-11-34
DO - 10.1186/1742-9994-11-34
M3 - Article
AN - SCOPUS:84899985713
SN - 1742-9994
VL - 11
JO - Frontiers in Zoology
JF - Frontiers in Zoology
IS - 1
M1 - 34
ER -