Cross breeding, need help.

[Steven@HumboldtHerps]

...where A,B,C,D, and E are monophyleic groups (upper left), where A,C, D, and E are paraphyletic groups (upper right), and C and D are polyphyletic groups. Every taxonomist is happy when he or she narrows it down to a monophyletic group (all descendents and common ancestors are addressed)
We are not happy with the para and the poly, but Thamnophis apparently still has us in turmoil with this.

Let's play pretend, and postulate what factors might explain the theory that elegans and ordinoides may share a more immediate common ancestor. We will also assume that there have been rare hybrids between the two. We will call the common ancestor of all "A". Let geographical area "X" (home to A) geologically split into areas "Y" and "Z" (assume habitat and dietary changes). After a period of isolation, let us assume that the divergence creates 2 new species, neither of which we will yet officially call ordinoides or elegans. They do not meet due to geographical barriers that now exist. Use the nodes that precede B and C, D and E; let's call the left node (B's and C's) the ordinoides line and the right (D's and E's) the elegans line.

Important (for this to make sense). Do not assume that the two separate lines break into their subsequent letters on the same geological time scale.

For that matter, imagine that the lines split into B and C, D and E pretty early on. Now let's say B is the ordinoides we know of today, and C is assumed a modern ordinoides, but still has some marginal genetic traits (possibly dormant) reminiscent of its old ancestor A... and we have not yet observed it! We will still call both B and C ordinoides because we know no better! Now, let's do the same for the elegans line; let's say that E is the modern elegans and D is an elegans with reminiscent traits of A (and we don't see it). If we change the geography again as does happen over time, let's say C and D meet, and they make babies!!! Yay! They had enough genetics in common to... ARE YOU GOING TO CALL IT A HYBRID???

I know this example was kind of silly, but it may be one of many that illustrates how variably inheritance plays itself out. We also can't discount the likelihood of convergent evolution among garters. Two separate species might look very similar due to a specific habitat and diet they both share. They might not be able to breed, but that might not stop them from looking alike.

Stefan originally turned me on to this study by Brownikowski and Arnold. I am not going to go into detail, but it really helps put the elegans world into perspective. You seriously begin to think about multiple migrations when you look at the map.