These flowers were able to bear fruit and reproduce, the researchers said, while those located farther from Pandanus plants often did not.
The team's findings, which appear in the April edition of the journal The American Naturalist, add to the growing number of examples of lizard pollination.
So far, almost all known cases occur on oceanic islands.
Jens Olesen, of the University of Aarhus in Denmark, is an expert on the little-studied phenomenon.
Olesen has assembled data showing that of more than 4,300 lizard species, only 71 are known to feed on flower nectar and, in the process, provide pollination services.
"Ninety-five percent of the flower-visiting lizard species are from islands," Olesen said.
Olesen and colleagues have suggested that a shortage of insects for the lizards to eat on remote islands may be what causes some species to become fruit- and nectar-eaters.
And Joan Roughgarden, an ecologist at Stanford University in California, thinks lizard pollination might evolve in island communities because pollinating birds and insects are in short supply.
"Lizards are available and other pollinators are not," Roughgarden said. "Bird faunas are usually [smaller] on islands, whereas lizards may be more abundant than on the mainland."
(Related news: "Buzz Kill: Wild Bees and Flowers Disappearing, Study Says" [July 21, 2006].)
Some island plants may even have special adaptations for attracting lizard pollinators.
Nectar of a Different Color
Trochetia flowers on Mauritius had puzzled scientists by producing nectar that is yellow or red in color. The nectar produced by almost all other flowers is clear.
In a separate paper last year, Hansen and colleagues said they had solved that mystery. Their experimental tests showed that colored nectar is an effective lure for enticing geckos to visit blossoms.
Hansen's team is now studying another rare Mauritian flower that appears to rely on geckos not only for pollination but also for seed dispersal.
"For both processes, the plants growing closer to Pandanus do better than ones further away," Hansen said.
Similar chains of positive interactions involving cover-providing plants and pollinating lizards may be widespread in island communities, he noted.
Maintaining such relationships may become increasingly important as native bird pollinators continue to decline and disappear.
"For island conservation management, the major take-home message is the need to promote habitat structural diversity, which provides [the foundation for] lizard-mediated interactions."
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