CGDP - Specific Goals      Part 3
     
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Phylogenetic Tests - Under Construction

 
 
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FLMNH 2005


     Phylogenies provide a relative framework of speciation events. Moreover, because the rate of change in the genes we are sequencing is relatively clock-like, molecular phylogenies can provide estimates of divergence times to determine whether species formed recently (1-2 million years ago) or whether they diverged much earlier (>10 million years). The inclusion of all living species is critical to these speciation tests. Divergence estimates are helpful to determine whether speciation events coincided with major tectonic, oceanographic or sea level changes, which are all well dated by geologists and paleoceanographers. Such concordance can be parsimoniously interpreted as causally linked to species formation.

     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.