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Molecular tracking of individual host use in the Shiny Cowbird – a generalist brood parasite

View Article: PubMed Central - PubMed

ABSTRACT

Generalist parasites exploit multiple host species at the population level, but the individual parasite's strategy may be either itself a generalist or a specialist pattern of host species use. Here, we studied the relationship between host availability and host use in the individual parasitism patterns of the Shiny Cowbird Molothrus bonariensis, a generalist avian obligate brood parasite that parasitizes an extreme range of hosts. Using five microsatellite markers and an 1120‐bp fragment of the mtDNA control region, we reconstructed full‐sibling groups from 359 cowbird eggs and chicks found in nests of the two most frequent hosts in our study area, the Chalk‐browed Mockingbird Mimus saturninus and the House Wren Troglodytes aedon. We were able to infer the laying behavior of 17 different females a posteriori and found that they were mostly faithful to a particular laying area and host species along the entire reproductive season and did not avoid using previously parasitized nests (multiple parasitism) even when other nests were available for parasitism. Moreover, we found females using the same host nest more than once (repeated parasitism), which had not been previously reported for this species. We also found few females parasitizing more than one host species. The use of an alternative host was not related to the main hosts' nest availability. Overall, female shiny cowbirds use a spatially structured and host species specific approach for parasitism, but they do so nonexclusively, resulting in both detectable levels of multiple parasitism and generalism at the level of individual parasites.

No MeSH data available.


Detail of the nests used by each of the 17 females studied: different breeding pair (black), same breeding pair – different nest (dark gray) and same breeding pair – same nest (light gray).
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ece32234-fig-0006: Detail of the nests used by each of the 17 females studied: different breeding pair (black), same breeding pair – different nest (dark gray) and same breeding pair – same nest (light gray).

Mentions: For eight females, eggs were found in nests of different breeding pairs (Fig. 6). For nine females, some eggs were found in nests of the same breeding pair. Four cowbird females parasitized only different breeding attempts, which were successive in some cases and interspersed in others, while for five females eggs were found in the same nest (Fig. 6). It is noteworthy that one female laid twice in the same nest of two different breeding pairs. This indicates that at least five of 17 females engaged in repeated parasitism. Use of the same nest was made with an interval of 1–4 days. A detailed evaluation of nest availability at the date when the female used the same nest for the second time showed that there were other options for laying: At least seven available nests were in the proximity of the nest used by female 7, four nests for females 8 and 10, and five nests for female 9. In the case of female 15, that showed repeated parasitism twice, there were three and one other suitable host nests available, respectively, at the time of laying repeatedly.


Molecular tracking of individual host use in the Shiny Cowbird – a generalist brood parasite
Detail of the nests used by each of the 17 females studied: different breeding pair (black), same breeding pair – different nest (dark gray) and same breeding pair – same nest (light gray).
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4979699&req=5

ece32234-fig-0006: Detail of the nests used by each of the 17 females studied: different breeding pair (black), same breeding pair – different nest (dark gray) and same breeding pair – same nest (light gray).
Mentions: For eight females, eggs were found in nests of different breeding pairs (Fig. 6). For nine females, some eggs were found in nests of the same breeding pair. Four cowbird females parasitized only different breeding attempts, which were successive in some cases and interspersed in others, while for five females eggs were found in the same nest (Fig. 6). It is noteworthy that one female laid twice in the same nest of two different breeding pairs. This indicates that at least five of 17 females engaged in repeated parasitism. Use of the same nest was made with an interval of 1–4 days. A detailed evaluation of nest availability at the date when the female used the same nest for the second time showed that there were other options for laying: At least seven available nests were in the proximity of the nest used by female 7, four nests for females 8 and 10, and five nests for female 9. In the case of female 15, that showed repeated parasitism twice, there were three and one other suitable host nests available, respectively, at the time of laying repeatedly.

View Article: PubMed Central - PubMed

ABSTRACT

Generalist parasites exploit multiple host species at the population level, but the individual parasite's strategy may be either itself a generalist or a specialist pattern of host species use. Here, we studied the relationship between host availability and host use in the individual parasitism patterns of the Shiny Cowbird Molothrus bonariensis, a generalist avian obligate brood parasite that parasitizes an extreme range of hosts. Using five microsatellite markers and an 1120‐bp fragment of the mtDNA control region, we reconstructed full‐sibling groups from 359 cowbird eggs and chicks found in nests of the two most frequent hosts in our study area, the Chalk‐browed Mockingbird Mimus saturninus and the House Wren Troglodytes aedon. We were able to infer the laying behavior of 17 different females a posteriori and found that they were mostly faithful to a particular laying area and host species along the entire reproductive season and did not avoid using previously parasitized nests (multiple parasitism) even when other nests were available for parasitism. Moreover, we found females using the same host nest more than once (repeated parasitism), which had not been previously reported for this species. We also found few females parasitizing more than one host species. The use of an alternative host was not related to the main hosts' nest availability. Overall, female shiny cowbirds use a spatially structured and host species specific approach for parasitism, but they do so nonexclusively, resulting in both detectable levels of multiple parasitism and generalism at the level of individual parasites.

No MeSH data available.