Bolitoglossa

Hand and foot morphology is strikingly diverse in an otherwise morphologically uniform group. While just under half of these species contain webbing between their fingers and toes, the remaining species experience little to no webbing and undergo elongation of their fingers and toes throughout development. Ultimately, the variation of foot morphology within this genus is primarily due to natural selection. Derived characteristics correspond to arboreal vs. terrestrial salamanders.[7]

• Webbed fingers – natural selection to improve terrestrial movement through water.
• Elongated fingers – natural selection of increased suction efficiency, favoring a larger surface area of the foot. This also selects for a decreased body size, enabling the salamander to cling trees more easily.

Tail autotomy refers to the salamanders’ ability to release or lose their tail if necessary. This is a common characteristic of nearly all salamanders and lizards. (See autotomy). It is particularly helpful to the salamander in escaping attacks from its predators. Once the tail has been lost, it can regenerate one time. After this regeneration, the tail is incapable of separation with regeneration.[8]

Bolitoglossa rostrata and B. subpalmata are two rare examples of poisonous salamanders within their genus. The poison is secreted through their skin as an antipredator mechanism. It is particularly toxic to certain snake species, rendering them immobile and unresponsive to external stimuli upon initial contact. The common defense tactic of these two species is to remain still in the presence of the snake until it makes initial contact (usually by the flickering of its tongue), and then run away as the paralytic poison begins to take effect in the snake.[9]

Tropical adaptation of the Bolitoglossa is thought to have evolved from North American plethodontids. Natural selection is responsible for morphological changes shifting from those supporting temperate environments to those supporting tropical environments such as Panama and Costa Rica.[10] Natural selection is thought to have resulted in genetic changes from physical adaptation. The main differences that have developed from natural selection affect the skull and bones of the feet in these salamanders. Due to these primary changes, secondary changes are believed to have followed, including:

• Body size
• Additional ossification of bones
• Webbing
• Ear structure

Phylogeny of this genus is partially dependent on its variations in bone structure due to the effects of natural selection over a long period of time.[11]

The first documented case of hybridization in tropical salamanders occurred between B. frankini and B. resplendens. This hybridization has taken a pervasive effect on the morphology of B. resplendens, whereas B. frankini seemed to maintain its same physical structure.[12]