Age at Birth Matters: The Impact of a Mother’s Age on her Daughters’ Reproduction

Posted on Tuesday, February 18, 2020

Yellow-bellied marmot female

Yellow-bellied marmot female at the Rocky Mountain Biological Laboratory. Photo credit: Svenja B. Kroeger

Daughters born to older mothers appear to be reproductively more successful throughout their lives, yet age at a faster rate, according to a University of Ottawa and University of Aberdeen study of yellow-bellied marmots.

“We were surprised to find the complete opposite to what is predicted by theory for aging individuals,” said lead author Dr. Svenja Kroeger, from the University of Aberdeen. “Being born to an older mother was not in fact detrimental but rather beneficial for reproduction. Daughters that were born to older mothers produced more offspring during their lifetime than daughters born to younger mothers.”

Julien Martin, Associate Professor in the Department of Biology at the University of Ottawa, along with Svenja Kroeger, his former PhD student at the University of Aberdeen (Scotland), Daniel Blumstein (University of California Los Angeles - UCLA), Kenneth Armitage (University of Kansas) and Jane Reid (University of Aberdeen) carried out statistical analyses using one of the oldest long-term studies of free-living wild mammals, the data set on yellow-bellied marmots living in and around the Rocky Mountain Biological Laboratory in the Colorado Rocky Mountains.

The team of researchers had access to detailed information covering a span of nearly 20 generations and looked at how many offspring each female had every year of their lives.

They also examined how the reproduction of daughters as they aged differed depending on how old their mother was at the time of birth.

“We found that daughter aging was affected by mother age at birth, and that this further depended on the environmental conditions the daughter was experiencing” Dr. Kroeger.

Yellow-bellied marmot mother and pup

Yellow-bellied marmot mother and pup at the Rocky Mountain Biological Laboratory. Photo credit: Julien G. A. Martin

Their work has direct implications for our understanding of senescence — or how organisms deteriorate with age.

“Much of the previous work assumed that an individual’s age acted directly to reduce performance due to senescence,” explained Dr. Julien Martin. “However, we have shown that the age of a parent also affects its offspring’s performance throughout the offspring’s life. Notably, our results show that the number of offspring produced by female marmots at every age and throughout their lives (referred to as lifetime reproductive success) depends on both their own age and the age of their mother at birth.”

The researchers believe their work should spark further studies on aging that investigate similar “cross-generational” effects.

“To date there is little evidence in natural populations that shows maternal age to be important for her offspring’s success as adults, let alone their aging,” added Dr. Martin.

The research was conducted between 2016 and 2019, primarily at the University of Aberdeen, in Scotland. All fieldwork was done in the East River Valley, at the Rocky Mountain Biological Laboratory in Colorado.

The paper Older mothers produce more successful daughters was published in Proceedings of the National Academy of Sciences (PNAS).



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