Pygmy Drosera Migrated from Western Australia to Northern South America!

Drosera meristocaulis

A recent article in Nature tipped me off to an older paper about Drosera meristocaulis. For those of you who don't grow this delightful species it is a pygmy sundew in all aspects, except that it is found only in a few valleys on the northern side of Pico da Neblina, a mountain in Brazil. Both morphological and DNA analysis have confirmed that D. meristocaulis is a member of the pygmy sundews.

Distribution Map

Importantly, this research on D. meristocaulis - and other research on the Drosera of South America - has revealed that this species, and perhaps others, migrated from Australia as a result of bird migration. What's fascinating about this is that DNA evidence has accumulated to indicate approximate dates of divergence for a number of species, indicating that the widespread belief in the post-1960s that continental drift explained the divergence of all species is incorrect.

The fact that this old, continental drift explanation does not hold water all the time makes sense. You can look at distribution maps of many carnivorous species and see how a distribution mechanism other than continental drift is necessary. Take Pinguicula hirtifolia, for instance. That species is found in one location in France as well as numerous locations in Italy and the Balkins. Or, in the context of D. meristocaulis, compare a map of Pico da Neblina with suitable habitats between the locations where pygmy sundews would ordinarily be found as part of Gondwana and that mountain, and it seems fairly obvious that some distribution mechanism had to deposit that species (or its ancestor) in that specific location post-separation of Australia and South America.

One last note, in Glistening Carnivores, Stewart McPherson erroneously writes that the last ancestor of D. meristocaulis and the pygmy sundews must have lived in Gondwana. In light of more recent studies, that section should be updated to reflect the above information.