[IzzieC (OP)]

Dominic asks...

Certain cats have a very distinctive mackerel pattern to their fur with the same distinctive lines which turn to spots at the hind quarters of the animal and sometimes even with the same white underside to the fish. Has anybody ascertained how this seeming genetic link came about or how two animals in such different environments produced the same patterns?

Can you help?

[Kryptid]

I imagine it's either a case of inheriting the pattern from a common ancestor (if the two species in question are closely related) or convergent evolution (if they are distantly related). Having spots or stripes helps break up the outline of an animal, making it easier for them to hide among structures such as tall grass or bushes. It can also make it harder to follow a single individual when it is in a herd (such as zebras). The underside being light is, I believe, a way to offset the fact that animals are darker on their undersides due to shadows. It's another aid with camouflage.

[RD]

Just because the patterns are similar it's not proof they're related ...



https://en.wikipedia.org/wiki/Patterns_in_nature#Spots,_stripes

[Bored chemist]

For flat things there are only 17 possible repeat patterns to choose from.
With billions of different life forms, the patterns are bound to be re-used.
https://en.wikipedia.org/wiki/Wallpaper_group

[Bill S]

The underside being light is, I believe, a way to offset the fact that animals are darker on their undersides due to shadows. It's another aid with camouflage.

If I remember correctly, the common hamster (C. crisetus) is one of the few species (the only one?) that is darker on the underside.  That must have some survival value. (?)

[evan_au]

the same white underside to the fish

If you look up towards the sky, it is very light. To hide from predators underneath you, you would want your underside to be as light as possible (some marine animals even have light-emitting microbes to match the brightness of the sky).

However, to hide from predators above you, you would want to be darker on top.
See: https://en.wikipedia.org/wiki/Countershading

[CliffordK]

There is a phenomenon called Convergent Evolution where unrelated species in similar environments, or with similar evolutionary pressures will adapt to have some of the same features. 

In the big cat world, one can have spotted cats on several continents: Cheetahs, Jaguars, Leopards, Bobcats, etc.  All a type of camouflage that is effective for their species.  Also spotted giraffes, and even fawns. 

I suppose Zebras and Tigers also have similar color patterns, but with different colors.  Camouflage? 

Thinking of zebras, apparently for a period, there were ships called Razzle Dazzle



Apparently it wasn't as much to hide as designed to disorient attackers.