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Sex-Dependent Carry-Over Effects Between Physiological State and Reproduction in a Passerine Species
G Szabó1,2,3, N Boross1,4, G Hegyi1,5
1Behavioural Ecology Group, Department of Systematic Zoology and Ecology ELTE Eötvös Loránd University Budapest Hungary.
Ecology and Evolution
|July 22, 2025
Summary
Carry-over effects impact reproduction differently in male and female collared flycatchers. Physiological changes like haematocrit and stress levels (H/L ratio) reveal sex-specific trade-offs and long-term fitness consequences.
Area of Science:
- Animal Ecology
- Physiological Ecology
- Evolutionary Biology
Background:
- Carry-over effects (COEs) link past life stages to future outcomes, yet are understudied in seasonal, short-lived animals.
- Investigating COEs between physiology and reproduction is crucial for understanding life history strategies.
Purpose of the Study:
- To examine temporal changes in haematocrit and heterophil granulocyte-to-lymphocyte (H/L) ratio within and between breeding seasons.
- To assess carry-over effects of haematocrit and H/L ratio on reproductive traits in collared flycatchers.
- To explore sex-specific differences in these physiological and reproductive relationships.
Main Methods:
- Monitored haematocrit and H/L ratio in collared flycatchers over multiple breeding seasons.
- Quantified reproductive parameters including breeding onset, clutch size, brood size, and prefledglings.
- Analyzed temporal variation and repeatability of physiological measures and their correlation with reproductive success.
Main Results:
- Haematocrit showed year-to-year variation and moderate repeatability, particularly in females. Male haematocrit decreased during breeding, linked to larger brood sizes.
- Female H/L ratio in one year correlated with reproductive effort in the previous year, indicating reproductive costs.
- Higher female H/L ratio during breeding predicted lower fledging success in the subsequent year, suggesting lasting stress impacts.
Conclusions:
- Carry-over effects between physiology and reproduction in collared flycatchers are sex-specific.
- Males face immediate self-maintenance vs. parental effort trade-offs, while females experience longer-term fitness consequences from reproductive stress.
- Distinct reproductive roles and energetic constraints likely drive these sex differences.
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