Post by dayhiker on Aug 16, 2017 13:36:32 GMT -8
While this starts off describing how cottonwoods have adapted to the changing river banks of the Western Cascades in Washington, it soon moves on to populars and aspens which are relatives , and then in how genetic studies have been used in taxonomity , and in studying the migration of trees back into areas after glacial retreat (there is evidence that many areas were repopulated from islands of refuge, rather than the far south, etc.
A bit slow but interesting, esp. since I have been studying trees from many angles of late.
One idea of defining a species was that it could not inter breed outside its own species. He puts forth the argument for that, but in the end demolishes it. I always wondered how a mutant could evolve so that it could only have sex with its self, and still reproduce (perhaps not a problem for plants as it would be for a mammal) , but he explains how there are many facets to prevention of breeding with another species of a tree, which could evolve slowly.
A bit slow but interesting, esp. since I have been studying trees from many angles of late.
One idea of defining a species was that it could not inter breed outside its own species. He puts forth the argument for that, but in the end demolishes it. I always wondered how a mutant could evolve so that it could only have sex with its self, and still reproduce (perhaps not a problem for plants as it would be for a mammal) , but he explains how there are many facets to prevention of breeding with another species of a tree, which could evolve slowly.