A new study about New Zealand's
extinct moa, involving acid baths and concrete mixers, by researchers from the
University of Canterbury and Landcare Research, has revealed a surprising
finding about their ability to disperse tree seeds.
For decades it had been assumed
that New Zealand's largest native fruits evolved to be eaten and spread about
prehistoric landscapes by the large extinct moa. The new study, published today
(18 April) in the prestigious Proceedings of the Royal Society B, casts
doubt on this theory.
By examining the seeds found in
23 preserved moa gizzard samples, and 152 ancient moa droppings, the authors
have shown that although moa consumed some of New Zealand's largest fruits (up
to 15mm diameter), their muscular, stone-filled gizzards pulverised all but the
tiniest of seeds. Only seeds less than 3mm diameter were found in the droppings
and were therefore capable of being dispersed by moa.
Lead author, University of
Canterbury (UC) Ecology Ph.D. student Jo Carpenter says that part of the reason
people had assumed that moa dispersed the large seeds – such as from miro,
mataī, hinau, pōkākā, and pūriri trees – was due to the thick seedcoats,
potentially requiring severe abrasion (as would have occurred in the
stone-filled gizzards of moa) for rapid germination.
"These seeds seem poorly
adapted for dispersal by birds that are alive today," Carpenter says.
"We were amazed to find that even silvereyes, which are one of New
Zealand's smallest fruit-eating birds, can disperse seeds significantly larger
than the giant moa were
dispersing."
To confirm their suspicions, the
researchers subjected miro and hinau seeds to a simulated passage through a moa
gut, by tumbling the seeds in a stone-filled concrete mixer followed by bathing
in a warm, weak acid bath. They found that this treatment did not actually
increase the speed of germination as had long been suspected. In fact, the
seeds still took between two and seven years to germinate.
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