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//]]></script><span class="glosstext" id="POPUP40025" style="display: none;"> A taxon is the individual unit whose evolutionary relationship is being investigated.  Depending on the study, “taxa” may refer to species, populations, individuals, or sequences within an individual.</span>, the root is sometimes given at the midpoint of the longest distance connecting two <a href="javascript:TextPopup(this)" id="HotSpot27639" class="glossterm">taxa</a><script type="text/javascript">//<![