Seasonal differences in baseline innate immune function are better explained by environment than annual cycle stage in a year‐round breeding tropical songbird

Autor: Maaike A. Versteegh, Chima Josiah Nwaogu, Will Cresswell, B. Irene Tieleman
Přispěvatelé: University of St Andrews. School of Biology, University of St Andrews. Centre for Biological Diversity, University of St Andrews. Scottish Oceans Institute, University of St Andrews. Institute of Behavioural and Neural Sciences, University of St Andrews. St Andrews Sustainability Institute, Tieleman lab, Behavioural & Physiological Ecology
Jazyk: angličtina
Rok vydání: 2019
Předmět:
0106 biological sciences
Rainfall
bird
Environmental change
QH301 Biology
Breeding
01 natural sciences
Songbirds
Dry season
Animal physiology
seasonality and wild animals
Passeriformes
Physiological Ecology
education.field_of_study
GE
TRADE-OFFS
WILD
environmental change
Annual cycle
Haemolysis
animal physiology
Brood patch
Female
Seasons
BDC
GE Environmental Sciences
Research Article
Wet season
BROOD-PATCH
DEFENSE
Population
rainfall
Zoology
ecological immunology
Biology
Ecological immunology
010603 evolutionary biology
QH301
Bird
medicine
NEWCASTLE-DISEASE
Animals
Seasonality and wild animals
education
Ecology
Evolution
Behavior and Systematics
BIRDS
010604 marine biology & hydrobiology
DAS
15. Life on land
Seasonality
Individual variability
PACE
medicine.disease
BODY-MASS
Immunity
Innate
individual variability
Animal Science and Zoology
REPRODUCTIVE EFFORT
Zdroj: The Journal of Animal Ecology
Journal of Animal Ecology, 88(4), 537-553. Wiley
ISSN: 1365-2656
0021-8790
Popis: Seasonal variation in innate immunity is often attributed to either temporal environmental variation or to life‐history trade‐offs that arise from specific annual cycle stages but decoupling them is difficult in natural populations.Here, we effectively decouple seasonal environmental variation from annual cycle stage effects by exploiting cross‐seasonal breeding and moult in the tropical Common Bulbul Pycnonotus barbatus. We test how annual cycle stage interacts with a key seasonal environmental variable, rainfall, to determine immunity at population and individual level. If immune challenge varies with precipitation, we might expect immune function to be higher in the wet season due to increased environmental productivity. If breeding or moult imposes resource constraints on birds, depending on or independent of precipitation, we might expect lower immune indices during breeding or moult.We sampled blood from 818 birds in four annual cycle stage categories: breeding, moult, simultaneous breeding and moulting, or neither. We quantified indices of innate immunity (haptoglobin, nitric oxide (NO x) and ovotransferrin concentrations, and haemagglutination and haemolysis titres) over two annual cycles of wet and dry seasons.Environment (but not annual cycle stage or interactions between both) explained variation in all immune indices, except NO x. NO x concentration differed between annual cycle stages but not between seasons. However, within the wet season, haptoglobin, NO x, ovotransferrin and haemolysis differed significantly between breeding and non‐breeding females. Aside from some recorded inconsistencies, population level results were largely similar to results within individuals that were measured repeatedly. Unexpectedly, most immune indices were higher in the dry season and during breeding.Higher immune indices may be explained if fewer or poorer quality resources force birds to increase social contact, thereby exposing individuals to novel antigens and increased infection risk, independently of environmental productivity. Breeding birds may also show higher immunity if less immune‐competent and/or infected females omit breeding. We conclude that seasonal environmental variation impacts immunity more directly in natural animal populations than via resource trade‐offs. In addition, immune indices were more often variable within than among individuals, but some indices are characteristic of individuals, and so may offer selective advantages if heritable.
Tropical environments are considered highly immune‐challenging for animals because of their relative higher organic productivity. However, this study from a seasonally arid tropical environment where annual cycle stages are decoupled from seasonal environmental variation, provides evidence that variation in innate immune function does not follow differences in annual cycle stages or simple environmental productivity pattern but may arise from interactions between individuals and their environment, and this may apply to variation in disease risk.
Databáze: OpenAIRE
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