The lack of sexual reproduction hasn't helped either—though mosses are able to persist through asexual means alone, the tiny, numerous spores produced in fruiting are needed to colonize new sites.
While all species of moss should be able to fruit, at least 10 percent of the 1,000 or more moss and liverwort species found in Britain have never been known to fruit there, said Rumsey. "In fact, some species are only known to have a single sex," he added.
Dangerous Liaison
For moss sperm, attempts at fertilizing the female of the species may be doomed before they even begin.
"Mosses…have a primitive fertilization system that involves sperm having to swim through liquid water from one plant to another," said Brent D. Mishler, a moss biologist and director of the Jepson Herbaria at the University of California, Berkeley. "Given that sperm have to swim, the sexes have to be [no more than] a few centimeters apart for fertilization to work," he said.
Unlike more-advanced land plants—such as pines and flowering plants—mosses haven't developed pollen. Pollen is used to carry a plant's male reproductive cells close to the female's egg cells before they are released.
Many species of moss have no known sex at all, said Mishler. As moss species have moved to drier habitats, over evolutionary time, there has been a trend to give up sex altogether, he said. Finding that sex still occurs in some species is important as it has implications for how the species should be conserved, he said.
"Something like 20 percent of British mosses are endangered," said Nick Hodgetts, a freelance moss biologist based in Lincolnshire, England, who formerly served on the Joint Nature Conservation Committee, a U.K. government conservation body. "The discovery of sexual reproduction is quite significant as it will greatly increase this species chance of survival," he said.
Rumsey and Headley now plan to attempt a little matchmaking by wedging small cushions of male moss next to female patches and vice versa.
The "discovery gives us a great opportunity to slow down, and possibly even halt, the extinction of a very interesting, but mostly overlooked species," said Rumsey.
|
SOURCES AND RELATED WEB SITES
|
