CAMERON, KENNETH M.1*, KENNETH J. WURDACK1, and RICHARD W. JOBSON1,2. 1The Lewis B. and Dorothy Cullman Program for Molecular Systematics Studies, The New York Botanical Garden, Bronx, New York 10458, USA; 2Department of Botany, University of Queensland, Brisbane, Queensland 4072, Australia. - Aldrovanda is sister to Dionaea (Droseraceae): molecular evidence for the common origin of snap-traps among carnivorous plants.
Molecular phylogenetic studies have shown that carnivory evolved
independently within several lineages of angiosperms. Carnivorous
plants attract, capture, and digest animals using either pitfall,
flypaper, bladder, or snap-traps. The latter mechanism is well known
as one of the fastest movements in plants and is employed by Venus'
flytrap (Dionaea). A similar trap is also used by the aquatic
waterwheel plant (Aldrovanda). However, this taxon has never
been included within molecular phylogenetic studies, and so it has
been unclear whether snap-traps evolved only once or more than once
among angiosperms. Aldrovanda's leaves resemble those of
Dionaea, its distribution and habit are reminiscent of
bladderworts (Utricularia), but it shares with sundews
(Drosera) many reproductive characters. For these reasons its
phylogenetic position and taxonomic status have been questioned. Using
sequences from nuclear 18S and plastid rbcL, atpB and
matK genes we show that Aldrovanda is sister to
Dionaea, and this pair is sister to Drosera. Our results
indicate that snap-traps are derived from flypaper-traps and have a
common ancestry among flowering plants, despite the fact that this
mechanism is utilized by a terrestrial species and an aquatic one.
Genetic evidence for the close relationship between these unique,
threatened organisms may help in understanding their biogeographic
history and unparalleled ecological adaptations, as well as assist in
their conservation.
Key words: Aldrovanda, carnivorous plants, Drosera, Droseraceae, molecular systematics, phylogeny