To test their hypothesis that the eastern moa (Emeus crassus), an extinct flightless bird from New Zealand, survived the Last Glacial Maximum (LGM) in a single glacial refugium in the southern South Island, a team of researchers from the University of Otago and the Université de Toulouse has analyzed ancient mitochondrial DNA extracted from several eastern moa specimens.
Moa browsed trees and shrubs within the forest understorey. Image credit: Heinrich Harder.
The moa is an order of giant, flightless birds comprising nine species that lived during the Late Quaternary epoch.
Moa species appear to have been adapted to different habitats and diets, inhabiting a wide range of environments, including subalpine areas, forest, and open shrubland-grasslands.
Consequently, they appear to have responded differently to climatic changes during the LGM (29,000 to 19,000 years ago in New Zealand): some moa species were able to track shifts in the distribution of their preferred habitat through time, while the distribution of other species may have been restricted to refugia as their favored habitats reduced in area.
The eastern moa is one species that may have contracted to a glacial refugium during the LGM: their fossils dating prior to and during the LGM are common in sites across the southern South Island and are absent from similarly aged deposits elsewhere, though they are widely distributed in post-LGM deposits.
“This species was spread across the eastern and southern South Island during the warmer Holocene period, but was restricted to the southern South Island during the height of the last Ice Age about 25,000 years ago,” said lead author Dr. Alex Verry, a researcher in the Department of Zoology at the University of Otago and the Centre for Anthropobiology and Genomics of Toulouse at the Université de Toulouse.
“This is in comparison to the heavy-footed moa (Pachyornis elephantopus), which retreated to both southern and northern regions of the South Island, while the upland moa (Megalapteryx didinus) inhabited four different areas.”
“The eastern moa’s response had consequences for its population size and genetic diversity — the LGM lead to a pronounced genetic bottleneck which meant it ended up with lower genetic diversity than other moa living in the same areas.”
In their research, Dr. Verry and his colleagues sequenced and analyzed the mitochondrial genomes from 46 eastern moa from throughout their geographical distribution — including the southern South Island — ranging in age from 14,000 to 500 years.
The results were consistent with a post-LGM increase in the population size and genetic diversity of eastern moa.
They also demonstrated that genetic diversity was higher in eastern moa from the southern extent of their range, supporting the hypothesis that they expanded from a single glacial refugium following the LGM.
“Our research is a rare example of the impacts of past climate change on extinct megafauna from New Zealand,” said co-author Dr. Nic Rawlence, director of Palaeogenetics Laboratory at the University of Otago.
“It also demonstrates how fossil remains and museum collections can be used to answer new questions about the past.”
The findings appear today in the journal Biology Letters.
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Alexander J.F. Verry et al. 2022. Genetic evidence for post-glacial expansion from a southern refugium in the eastern moa (Emeus crassus). Biol. Lett 18 (5): 20220013; doi: 10.1098/rsbl.2022.0013
Source link: https://www.sci.news/paleontology/eastern-moa-distribution-10796.html
