Yesterday I presented some photographs and descriptions by biologist Dennis Hansen of his work on the isolated island of Mauritius. That only scratched the surface of the amazing biology of the endemic species on this island, and I want to finish up this brief lesson with some more show-and-tell.
Dennis also sent me an reallly nice paper written by him and Christine Müller in The International Journal of Plant Science (reference below). It describes how one species of very rare Mauritian plant seems to be both pollinated and have its seeds dispersed solely by a lovely endemic gecko. Maybe I’m wrong, but I think this is the only case of a plant that depends entirely on a lizard for reproduction. But I’ll let Dennis tell the tale (his photographs are below, and I suspect that if you leave your email address in a comment, he’ll send you a pdf of the paper, which is well worth reading):
Anyway, here’s a handful of shots from the field—one of my favourite Mauritian endemic plants, Roussea simplex, being both pollinated (photo 1 &2) AND having its seeds dispersed (photo 3) by the same gecko species, the blue-tailed day-gecko, Phelsuma cepediana. It’s a cool system, but under threat from invasive ants that chase off the geckos (!), and invasive plants that outcompete Roussea simplex. There are likely less than 150 plants left of this species. Don’t worry. In Mauritius, that’s plenty (like Douglas Adams recounted for the Rodrigues fruit bat in ‘Last Chance to See‘ — “don’t worry, there are HUNDREDS of bats left!”). Yes, many species—and even more interactions—are in trouble indeed. The paper about this interaction even made it to the front cover of a journal from your university press (Int J Plant Sci). Who cares that this paper probably will pick up less than 10 citations in its lifetime—it made me feel immensely privileged to have studied this interaction. If nothing else, then because it means that it will not—unlike Quammen puts it for The Song of the Dodo—forever remain unbeknownst to us, because no one took the time to sit down in the forest and listen (or watch, in this case).
Here’s a photo I’ve taken from Hansen and Müller’s paper showing the lizard with a smear of pollen on its head (arrow). The pollen is mixed with a sticky, viscid residue, and so is unsuitable for disperal by insects, but fits nicely on the lizard’s head. And when the lizard goes to the next plant for nectar, the pollen is transferred to the stigma.
Curiously, though seed dispersal appears to rely entirely on the gecko, seeds that were recovered after passing through geckos, or taken directly from the plant, were never seen to germinate. They were all attacked by a fungus that killed them. Perhaps the specific microclimate of the forest floor somehow facilitates seed germination.
But wait—there’s more. Again, I defer to Dennis’s descriptions:
Colea colei: an amazing little understory plant from the rainforest in Mauritius, sort of like a thin, upright liana up to a few meters high, with a tuft of green leaves at the top. It is cauliflorous, with the gorgeous flowers emerging straight from the stem, all the way down to the ground (don’t get me started on the cool evolutionary ecology of that trait).
Telfair’s skink [Leiolopisma telfairii] with Pandanus fruit: from Round Island, north of Mauritius. Heaven on Earth, that island is. Home to many of the surviving endemic reptiles of Mauritius. I think of Churchill with a cigar whenever I look at this photo. [JAC: this island is the only place known to harbor this reptile.]
One of my favourite geckos, the Ornate Day Gecko, Phelsuma ornata:
Two of the huge orb-weaving spider Nephila inaurata & its gecko-victim: sometimes male geckos will jump off the surface they are on, if threatened by a larger male. In this case, the poor fella jumped right into the web of the spider! The second photo shows the gecko two hours after the spider’s injection of digestive enzymes (several points of injection). Kinda looks like it’s been hit by a flame thrower.
One of a Dombeya flower—notice the secondary pollen presentation on the tip of the petals, and the yellow nectar at the base of the petals. Coloured nectar is an incredible subject on its own, but I will refrain from harping on at great length here.
One of Telfair’s skink, Leiolopisma telfairii, on a palm inflorescence. All the yellow spots in its face are pollen grains, too.
Some of the largest surviving Phelsuma [genus of "day geckos"] gecko, Guenther’s gecko [Phelsuma guentheri]:
Some more of the Blue-tailed Day Gecko, P. cepediana, pollinating flowers of Trochetia blackburniana (notice the size difference between the large male hanging off the flower, and the small female/juvenile almost disappearing into the flower)
Thanks to Dennis for sharing his work and photos with us.
Hansen, D. M. and C. B. Müller. 2009. Reproductive ecology of the endangered enigmatic Mauritian endemic Roussea simplex (Rousseaceae). Int. J. Plant Sci 170:42-52.