Within an ecotype — a forest type, a river pool, a field — species tend to stabilize and become fewer. Species and variation are most abundant where ecotypes meet: along the edges of forest and meadow, seashore
and land, river and ocean.

Interesting things happen along borders —
transitions — not in the middle where
everything is the same.

In the beginning there were three sexes, one
entirely male, one entirely female, and also
a third having the characteristics
of both men and women.