2024-01-10 07:00:11
Carnivorous plants fascinate, by the originality of their diet, but also by the diversity of devices they use to trap the insects on which they feed: glue, jaws, digestive enzymes, fatal urns… Plants of the genus Nepenthessome of whose leaves take the shape of a reservoir topped with a cover, drown their prey, which once dissolved provides them with nutrients that are sometimes rare in their environment.
“Nepenthes gracilis”, found in the high altitude forests of South-East Asia. ULRIKE BAUER
In 2012, Ulrike Bauer (University of Bristol) described how the species Nepenthes graciliswhich is found in the high altitude forests of South-East Asia, had added a refinement to this device: it was enough for a drop of rain to fall on the lid for the vibration generated to project the insects attracted below into the deadly bath.
In Science from January 4, the researcher describes a similar mechanism observed in another carnivorous plant, Nepenthes pervillei, endemic to the Seychelles and 4,000 kilometers from its cousin. With her colleagues, she proposes an evolutionary scenario to explain the appearance of such a complex device in these two species. The trap can, in fact, only work if three different characteristics are simultaneously present: first of all, the cover must be horizontal so that the catapult effect propels the insect directly into the urn; that this cover has spring so that the energy of the drop is transferred to the prey; that the lower part of the lid is just slippery enough for a fly or ant to venture in, but comes off on impact with the drop.
A diabolical “diving board trap”
These are what we call composite characters, which once assembled contribute to an effect that the appearance of each of them independently could not have allowed us to guess. We sometimes speak of exaptation to designate physical characteristics which come to fulfill functions which they did not have when they appeared – such as feathers, for flight, which were originally thermal regulators.
“Explaining the origin of composite traits has intrigued biologists since Darwin, because it involves the coordinated evolution of multiple independent components”write Ulrike Bauer and her colleagues, who took advantage of the amount of knowledge accumulated on more than fifty carnivorous plants of the genus Nepenthes to try to model the emergence of the diabolical “diving board trap” of gracilis et pervillei. The researchers compared, for example, the composition of the treacherous wax crystals covering the lower part of the umbrella, and the angle of the latter in relation to the horizontal, or even the type of twist induced by the fall of a drop.
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