Molecular phylogenies can also determine whether proposed subspecies are distinct populations. If geographically restricted subspecies are all most closely related in the phylogenetic reconstructions, this infers that there is little or no exchange of larvae with other members of the species. If so, these restricted, distinct subspecies can be thought of as incipient (or potential) species. Their geographic ranges suggest where speciation is presently occurring throughout the Indo-Pacific. Also, their range boundaries should be examined to see if they are the same as any oceanographic barrier to genetic exchange. We must remember that we are observing just a single time slice in an extremely dynamic and changing world.