Geographical variation in plasma bactericidal ability of breeding tree swallows (Tachycineta bicolor)
- 1Princeton University
Abstract
Immune defenses may vary across environments due to differences in life history or abiotic and biotic characteristics, but few studies have compared the strength of immune responses across broad geographical gradients. Here we investigated how bacteria killing ability (BKA), a measure of constitutive innate immune function, varies among populations of tree swallows (Tachycineta bicolor) inhabiting different environments. We hypothesized that populations living in unpredictable environments, which also have shorter breeding seasons and thus fewer opportunities to renest in the event of reproductive failure, would invest in reproduction at the expense of immunity. To test this hypothesis, we measured BKA and monitored reproductive activity in four populations located across most of the breeding range of tree swallows, in Tennessee, New York, Wyoming and Alaska. Consistent with our predictions, BKA was lowest in Alaska and Wyoming and highest in Tennessee. In most populations BKA was also lower during incubation than during nestling provisioning, and lower in males than in females. These results suggest that the high reproductive investment seen in populations experiencing more unpredictable breeding conditions may come at a cost to immune function. While reduced immune investment could increase susceptibility to parasites, this potential cost is likely offset by lower parasite pressure in these environments, limiting the need for maintaining strong constitutive innate defenses like BKA.
Related
- Geographical and Climatic Variation Is Associated with Essential Oil Chemotypes While Preserving Biological Activity in Athamanta sicula L.
- Integrated metabolomic, transcriptomic and computational analyses reveal geographical variation and potential anti-osteoarthritis bioactive compounds in Arenga pinnata pith
- Populations of cooperatively breeding birds are buffered against annual variation in precipitation and temperature
- Development and application of a 40K liquid chip enriched with structural variation markers for watermelon breeding
- Whole genome resequencing in tomato reveals variation associated with introgression and breeding events
BibTeX
@misc{oordt2026geographical,
title = {{Geographical variation in plasma bactericidal ability of breeding tree swallows (Tachycineta bicolor)}},
author = {D. A. Chang van Oordt and C. Zimmer and C. C. Taff and D. R. Ardia and A. P. Rose and D. A. Aborn and L. S. Johnson and T. A. Ryan and J. J. Uehling and M. N. Vitousek},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.25.754392},
url = {https://www.biorxiv.org/content/10.64898/2026.09.25.754392v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Geographical variation in plasma bactericidal ability of breeding tree swallows (Tachycineta bicolor)
AU - D. A. Chang van Oordt
AU - C. Zimmer
AU - C. C. Taff
AU - D. R. Ardia
AU - A. P. Rose
AU - D. A. Aborn
AU - L. S. Johnson
AU - T. A. Ryan
AU - J. J. Uehling
AU - M. N. Vitousek
PY - 2026
DA - 2026/09/25
PB - bioRxiv
DO - 10.64898/2026.09.25.754392
UR - https://www.biorxiv.org/content/10.64898/2026.09.25.754392v1
AB - Immune defenses may vary across environments due to differences in life history or abiotic and biotic characteristics, but few studies have compared the strength of immune responses across broad geographical gradients. Here we investigated how bacteria killing ability (BKA), a measure of constitutive innate immune function, varies among populations of tree swallows (Tachycineta bicolor) inhabiting different environments. We hypothesized that populations living in unpredictable environments, which also have shorter breeding seasons and thus fewer opportunities to renest in the event of reproductive failure, would invest in reproduction at the expense of immunity. To test this hypothesis, we measured BKA and monitored reproductive activity in four populations located across most of the breeding range of tree swallows, in Tennessee, New York, Wyoming and Alaska. Consistent with our predictions, BKA was lowest in Alaska and Wyoming and highest in Tennessee. In most populations BKA was also lower during incubation than during nestling provisioning, and lower in males than in females. These results suggest that the high reproductive investment seen in populations experiencing more unpredictable breeding conditions may come at a cost to immune function. While reduced immune investment could increase susceptibility to parasites, this potential cost is likely offset by lower parasite pressure in these environments, limiting the need for maintaining strong constitutive innate defenses like BKA.
ER -