een used):</p>
<p>&#160;</p>
<p><span style="font-weight: bold;">Use a single fixed time of divergence</span> 
 - in this case, the clock calibration is simply the (relative) height 
 of the target node divided by fixed the time of divergence, and then this 
 calibrated clock rate sets the scale to convert all relative times in 
 the tree into absolute times.</p>
<p>&#160;</p>
<p><span style="font-weight: bold;">Use a fixed evolutionary rate</span> 
 - using this option one can define a global evolutionary 