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Carnivorous Plants in the Wilderness
by Makoto Honda



Carnivorous Plants
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Snap Trap - Evolution

2017-April-06:  Under construction  ------------------  Observations of the trap

Molecular phylogenetics strongly points to a common origin of the two snap traps (Aldrovanda & Dionaea).

This most likely means that the snap trap evolved only once; therefore, the basic mechanism for these snap traps must be the same... actually identical...
It is widely accepted that, in the case of Dionaea, the snapping of a trap leaf involves buckling. This is due to the initial convex curvature (doubly-curved) of the open trap lobes of a mature specimen. This "snap-through" buckling (or "flipping") does increase the speed of trap closure - a little. However, it has to be understood that the buckling, if it does happen, is not the main, driving force of the swift leaf closure, but rather, a result of it. The main cause of leaf closure is the pressure differential created between the opposite sides (upper & lower) of the trap lobes..... The same mechanism is responsible for the swift snap trap of Aldrovanda (no buckling here, though).

The molecular evidence further indicates that Aldrovanda and Dionaea form a clade that is sister to Drosera (sundews). This strongly suggests that the common ancestor of Aldrovanda & Dionaea came from an ancient sundew-like plant. This implies the mechanism responsible for the snap traps is most likely derived from a sundew-like plant --- its tentacle bending and  leaf folding.

The basic mechanism for leaf motion common throughout Drosera-Aldrovanda-Dionaea evolution is most likely to be a sudden (or relatively quick) drop of turgor pressure on one side of the structure in question, creating an imbalance of pressure on the structure to cause it to bend.... In this process, the other side (epidermis) might be forced to stretch a bit .... The recovery of the bending (or snapping for that matter) is achieved as a result of the side (epidermis) that lost turgor pressure restoring its lost pressure and then some to counter the stretch of the other side. This is accomplished by slow, normal, actual growth.

1.  Drosera (sundews) ---- Illustrations

 Tentacle bending (nastic/tropistic) - leaf folding
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2.  Aldrovanda (waterwheel plant) ---- Illustrations

 motor region  - narrowing (free side/lower side)
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3.  Dionaea (Venus flytrap) ---- Illustrations

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EVOLUTION : DROSERA - ALDROVANDA - DIONAEA ------------ Which came first..... Aldrovanda, of course!

Molecular phylogenetic reconstruction clearly points to the common origin of these snap traps....

The common ancestor of these snap traps diverged from the ancient sticky-leaved sundew plant. That is the ancestor of the extant basal taxa such as D. regia  (see midrib)   

Comparison of flower parts:   Petal / sepal / seed / pollen / stigma / placenta

Trap tilt - Ontogeny recapitulates phylogeny.... see Lloyd, Darwin
 

 

Copyright (c) 2017 Makoto Honda. All Rights Reserved.

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