>>During that discussion I started to fumble the terms analagous, homoplasic, parallelism and convergence and seek your clarification. After being out of the lab for almost two years I'm a bit "rusty" in science speak. My science library was lost in a flood last year so I have no immediate reference source.
>>
>>I'd appreciate your comments on the following hypothetical example.
>>
>>In this example we have two species of aglyphous snakes that give rise to two separate lineages of snakes with OD.
>>
>>The two snakes species are closely related enough that the specific teeth giving rise to the OD are homologous.
>>
>>Would the resultant OD be an example of homoplasy since they were independent origins?

The opisthoglyphous dentition in the two lineages would be a case of homoplasy, since the opisthoglyphous dentition would have evolved simultaneously. On the other had, the posterior maxillary teeth involved would be homologous in the sense that they are both posterior maxillary teeth.

A parallel example would be the wings of a bird and a bat: their function as wings is a case of homoplasy, since it evolved independently, but they are homologous in the sense that they are both types of vertebrate forelimb.


>>Or would they be an example of parallelism since OD evolved through an identical evolutionary pathway, albeit independent of each other?

That as well. Parallel evolution is a type of homoplasy. Homoplasy is basically the catch-all term for "noise" in a phylogenetic analysis. Homoplasy is caused by 3 phenomena:

- convergence, where two lineages arrive at sharing a derived condition from a different starting point (e.g., green pattern with white spots in Corallus caninus and Morelia viridis, evolved from somewhat different ancestral patterns).

- parallel evolution, where two lineages independently acquire the same derived character state from the same starting point (e.g., flat tail in Laticauda and sea snakes)

- reversal, where a derived condition is lost again (e.g., venom in North American rat and king snakes).

In practice, parallel evolution and convergence can be difficult to distinguish, but, in any case, result in a derived condition being acquired independently by multiple lineages.

Hope this helps.

Cheers,

Wolfgang
-----
WW Home

[ Show Entire Thread ]