Matteo Beccardi (he/him) provides the story behind her paper, “Inbreeding accelerates reproductive senescence, but not survival senescence, in a precocial bird“, which was shortlisted for this year’s Elton Prize. We also hear a little about her journey into animal ecology.

About the paper

Inbreeding has long been recognized as a factor that reduces fitness across a wide range of taxa. However, the influence of inbreeding on age-related declines in organismal functions remains incompletely understood. In this study, we sought to address this knowledge gap by studying how inbreeding affects senescence dynamics in the Japanese quail (Coturnix japonica), with particular emphasis on the differential effects on reproductive and survival senescence. Given the theoretical expectation that the strength of natural selection weakens with age, leading to an accumulation of deleterious alleles that manifest their effects later in life, we tested the hypothesis that inbreeding depression should become more pronounced as individuals age.

To investigate this, we performed controlled matings between related and unrelated individuals and systematically monitored their offspring throughout their entire lifespan. This approach allowed us to quantify the effect of inbreeding on multiple fitness components, including hatching success, the age of sexual maturity, laying rate, and longevity. Our results revealed a clear pattern: inbreeding significantly accelerated reproductive senescence, with inbred females exhibiting a steeper decline in egg-laying rates at later ages compared to their outbred counterparts. This finding is consistent with the hypothesis that inbreeding depression intensifies with age in traits directly linked to fitness, potentially due to an increased expression of recessive deleterious alleles affecting physiological processes related to fecundity.

Interestingly, while inbreeding reduced overall lifespan, its impact on daily survival did not appear to increase with age. This suggests that although inbred individuals were generally more likely to die younger, their mortality rate did not increase at a greater rate with age, compared to outbred individuals. This pattern challenges the assumption that inbreeding should universally exacerbate senescence across all fitness components and highlights the possibility that the genetic architecture underlying survival and reproductive ageing may be distinct. One potential explanation for this discrepancy is that deleterious alleles influencing survival may be purged already earlier in life through selective mortality, whereas those affecting reproductive performance without a concomitant effect on survival continue to accumulate and manifest their effects with age.

Our study also underscored the broader consequences of inbreeding for early-life fitness. We found that inbreeding was associated with reduced hatching success and delayed sexual maturation, reinforcing the notion that its negative effects extend beyond late-life senescence and shape individual performance, and intra-generational purging, from the very outset of development.

One of the key challenges in this study was collecting a long-term dataset spanning the entire lifespan of a large sample of individuals under controlled conditions. This allowed us to rigorously assess age-specific patterns of inbreeding depression while minimizing confounding effects related to environmental variability. Future research should explore whether similar patterns are observed in wild populations, where environmental stressors and social interactions may modulate the strength and direction of inbreeding effects on senescence. Additionally, genomic approaches could help identify specific loci associated with age-dependent inbreeding depression, shedding light on the mechanisms underlying these patterns.

About the author

Ever since my childhood I am fascinated by the natural world around me, and in addition to my great passion for ornithology, this led me to study first Biology and then Evolutionary Biology at the University of Padova (Italy). Currently I am a PhD student at the Institute of Avian Research in Wilhelmshaven, Germany. One of the main aims of my PhD programme is the investigation of how inbreeding affects various traits and thereby shapes individual life histories. I would advise people in my research field to always embrace the unpredictability that working with live animals encompasses, and always stay open for new research directions. Just go where the possibilities lead you.

Personal page at my institute’s website: https://ifv-vogelwarte.de/en/institute/staff/matteo-beccardi