National Geographic News
Moss on Kohala Mountain, Hawaii.
Sphagnum palustre blankets the forest floor on Hawaii's Kohala Mountain.

Photograph courtesy Sara C. Hotchkiss

Ker Than

for National Geographic News

Published December 30, 2011

A moss spreading throughout the Hawaiian Islands (map) appears to be an ancient clone that has copied itself for some 50,000 years—and may be one of the oldest multicellular organisms on Earth, a new study suggests.

The peat moss Sphagnum palustre is found throughout the Northern Hemisphere, but the moss living in Hawaii appears to reproduce only through cloning, without the need for sex or production of spores.

(See "Group to Clone California Redwoods.")

All the moss populations sampled share a rare genetic marker, which suggests they're descended from a single founder plant that was carried via wind to Hawaii tens of thousands of years ago.

Since S. palustre is unisexual, having male and female plants, sexual reproduction would not have been possible, said study co-author Eric Karlin, a plant ecologist at Ramapo College in New Jersey.

"You would expect one founding plant to have this rare trait. However, it is unlikely that there were many founding plants with each one having the same rare trait," he said.

Ancient Moss Surprisingly Diverse

Fossilized S. palustre moss remains have been found in 23,900-year-old peat near the summit of Kohala Mountain on Big Island (Hawaii). (See your Hawaii pictures.)

From these remains, Karlin and colleagues inferred that the moss had been in Hawaii at least that long, and perhaps longer.

To find out, the team analyzed the genetic diversity of the current population of moss on the island and determined a mutation rate. Using this mutation rate, they estimated how long it took for the different moss populations to get to where they are genetically—about 50,000 years.

The genetic analysis also revealed surprising diversity—challenging the popular assumption that clones are genetically drab because they can't swap DNA through sex.

"They're not identical because mutations are always occurring," Karlin said. "So given a sufficient period of time, you will find that offspring from a clone may be genetically different from one another."

"However, there are probably other plant populations on islands having a similar history that we haven't studied yet."

Alien Moss a "Problem" for Local Plants

Given the absence of sex, the moss has been likely "trapped" on the Kohala summit, Karlin said. Sexual reproduction—which creates airborne spores—would be required for the plant to move elsewhere.

But people have also lent a helping—though unwitting—hand in the moss's spread. In the past century, people have used the moss for packing material, in doing so moving the species across Big Island as well as on the island of Oahu.

(See "Alien-Wasp Swarms Devouring Birds, Bugs in Hawaii.")

"The peat moss has had explosive growth where it was introduced, especially on Oahu," Karlin said.

The moss's success comes at the cost of other local plants, however. "It's a problem," he said.

"The moss completely changes the ecology of the ground layer. Instead of there being soil, there is a solid carpet of moss, and the seeds of many of the local plants don't grow in the moss layer."

The research is detailed in the latest issue of the journal New Phytologist.

1 comments
Brandon Sutton
Brandon Sutton

This article strikes me as interesting for several reasons but chiefly I am struck by the excellent breakdown of how epi-genetics allow organisms to respond to local conditions thus allowing for genetic expression.  I find this interesting because where I'm from, Embarrass Minnesota, the Canadian shield extends down into the US and sphagnum bogs are extensive where I believe similar mosses are considered a "climax forest species".  I was wondering how these biomes like pothole bogs and glacial dome bogs were going to respond to the pressures of climate migration.  They seem to have more tools in their genetic toolbox than I understood!

I am struck by the intelligence of mosses, an ancient race, and how the animistic people of the heath bogs understood places (like mountain summits, trees, sources of water) as having genius loci--sprite, fairy, naiad, et cetera--the ability organisms to respond to local conditions and change to adapt--intelligence of the extensive yet simple mathematics of local conditions expressed through genetic change.  Indeed those seeds that "will not sprout in mossy conditions" are merely failed attempts at establishing a mutualistic system like there is in my bogs at home: carnivorous plants ericaceous understory--heathers.  Have heathers and pitcher plants evolved with the sphagnum bogs in Hawaii?  Can I try to farm my Embarrass bog plants in Hawaii?

Other organisms like aspens evolved cloning to reproduce when sexual reproduction was limited by climate are also very ancient--clonal colonizing seems to be a successful expression of life when confronted by sterile conditions.  Island evolution will instruct us on how life responds to rapid climate change and these mosses are the perfect place to start.  Let's take a clue and not fear the introduction of "alien species" as being anything other than what they are: vehicles of evolution to allow local conditions to create genetic diversity.  

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