Evolution or coincidence:

[ewurm]

Can these two fish possibly not be very closely related? They aren't listed under the same genus, yet the tail markings are a dead ringer. The body shape is similar, and the mouth shape does have variance. The native range is not shared, however. Opinions?

 

[cypher1024]

Haha. I have been looking at R. Trilineata because P. Denisonii are too expensive.

If you go back far enough, everything shares a common ancestor.
While these two do look similar (that's why I'm considering the Rasbora), they differ in a number of ways. If you take a close look at the fins, the Denisonii has pointed tips to its tail, but rounded fins almost everywhere else. The Rasbora is the opposite - rounded tail and pointed fins.

 

[skjl47]

Hello; Cannot recall just now what it is called, but there is a part of evolution theory that covers this. Animals or plants that start out with very different characteristics will begin to have very similar traits and characteristics if they live in a similar environment for a long period of time.
Perhaps convergent evolution or parallel evolution??

 

[wantokeeptrout]

Hello; Cannot recall just now what it is called, but there is a part of evolution theory that covers this. Animals or plants that start out with very different characteristics will begin to have very similar traits and characteristics if they live in a similar environment for a long period of time.
Perhaps convergent evolution or parallel evolution??

definately convergant evolution. parallel is when the populations are close by. Another prime example is hedgehogs and echidnas

 

[ewurm]

What I mean't to say was, is their an evolutionary reason for this particular marking, or is it just a coincidence. Of course the marking is evolved, just why is the pattern the same? Is it advantageous to the animal in their native ranges, are they somehow very closely related, or is it not related at all? I'll look for parallel and convergent evolution. Don't recall reading on it. Thanks guys!