Hi simonts
If you are lucky enough to have found some true wild caught guppies, get them; they are not easy to get these days. Ask the owner or manager about their origins; he or she should know or be able to find out from the distributor.
Years ago, guppies (which were then all wild, or bred from wild ones) were my first fish, and I would love to have some of them again.

They were brightly colored and had certain patterns among their markings. Some of these markings had names such as, lace, peacock, birds eye, chain, and others. They were sturdy fish, easy to raise, and each new generation would have different colors and patterns than the ones before.
Guppies sold these days have been over bred to where they have little resemblance to anything nature created. While they are lovely as they are, their tails and fins are overly long, their size is huge compared to natural ones, and they no longer have the array of patterns the wild ones have.
Endlers are different fish entirely, but they do interbreed. If you are looking for wild guppies or Endlers, beware that the lfs does not sell you real males, but substitute "feeder" guppies for the females. This has been known to happen, and while they look the same as wild females, future generations will lose their desired markings.
Crossing any of these species will only result in smaller, and weaker specimens, and they will become poor quality fish that no one will want to buy.
