Monash scientists discover key to predicting fitness of birds

A male purple-crowned fair-wren

An international study led by Monash biologists has found that the length of a baby bird's telomeres, the DNA caps that protect chromosomes, can predict its future fitness.

A male purple-crowned fair-wren.
Credit: Laurent Lermusiaux

Associate Professor Anne Peters, from the Monash School of Biological Sciences and Research Fellow Dr Justin Eastwood studied wild purple-crowned fairy-wrens, an endangered species, at the Australian Wildlife Conservancy’s Mornington Sanctuary. Their work, funded by the Australian Research Council and was published today in the journal Molecular Ecology.

Telomeres are segments of chromosomal DNA that protect coding DNA and shorten in response to cell replication and stress; when they become critically short cells stop functioning, which is seen at the organismal level as ageing.

At any particular age, individual telomere length reflects growth, inheritance and lifetime accumulated stress.

“We know that longer telomeres are a desirable attribute, as they predict better survival prospects. Here we asked if this is also true for telomeres very early in life, and whether it matters for evolutionary fitness,” said Associate Professor Peters.

To test this, Associate Professor Peters and Dr Eastwood measured the length of nestling telomeres from DNA samples across several cohorts. Each individual was then followed for the remainder of their life, up to 12 years, with everything about their lives recorded, including social position, number of offspring and when they died. This allowed the team to investigate whether early-life TL predicts evolutionary fitness prospects.

Associate Professor Peters said this type of data was extremely rare due to the major logistical challenges of collection.  “This is the only study on early-life telomeres to include complete lifetime reproductive success data,” she said.

“For the first time in any species, we demonstrate the manner in which early life telomere length is related to fitness prospects,” she said.

“We found that telomere length in wild nestling birds, only seven days old, was able to predict how their late-life would unfold.

“Longer nestling telomere length was positively related to lifespan, breeding duration, and lifetime reproductive success. In other words, longer telomeres in infancy equal more offspring and a greater genetic contribution to the next generation.”

This indicates that telomeres might be broadly important for late-life performance, and even very early in life, serve as a predictor of fitness.

Dr Eastwood, first author of the study, said that the physiological link underlying the frequent observation that poor conditions experienced early in life have negative consequences much later in life, is hotly debated.

“Here we show that telomeres may provide that missing link because of their association with ageing,” he said

“The ubiquity of telomeres across all eukaryotes, which includes all complex life forms including humans, highlights the generality of our findings and has major implications for several fields including the ecological, evolutionary, developmental and biomedical sciences.”

The team is now investigating the environmental factors that influence nestling telomere length to help understand their effects on lifespan and reproductive success.


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Silvia Dropulich
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