Snap Trap - Evolution
Last update : 2017-June-17 ------------------ 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...
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
bending (nastic/tropistic) - leaf folding
2. Aldrovanda (waterwheel plant) ---- Illustrations
- narrowing (free side/lower side)
3. Dionaea (Venus flytrap) ---- Illustrations
EVOLUTION : DROSERA - ALDROVANDA - DIONAEA ------------ Which came first..... Aldrovanda, of course!
Molecular phylogenetic reconstruction clearly points to the common origin of these snap traps....
Molecular evidence further suggests the common ancestor of these snap traps diverged from the ancient sticky-leaved sundew plant - the ancestor of the extant basal taxa such as D. regia (see midrib)
flower parts: Petal / sepal / seed / pistil / stamen / pollen / stigma / placenta
1) Lloyd - In Venus flytrap, the trap tilts to the right - particularly in younger plants, just like the clear bend in the Aldrovanda trap (see Lloyd/Darwin) --- a distinct advantage for Aldrovanda (no benefit for Dionaea).
2) Lloyd comments on a young Venus flytrap (2 mm trap) ----> "The number of parenchyma cells between ranged from two to four courses with large interspaces, in this feature again resembling the mature leaves of Aldrovanda much more than do the thicker mature leaves of Dionaea."
Copyright (c) 2017 Makoto Honda. All Rights Reserved.