n Southern African Forestry Journal - Quantifying the geographic range of var. in Southern Mexico using morphologic and RAPD marker data : scientific paper

Volume 2001, Issue 192
  • ISSN : 0038-2167



<i>Pinus patula&lt;/i&gt; var. &lt;i&gt;longipedunculata&lt;/i&gt; occurs in southern Mexico, but the extent of its geographic range is poorly defined. Trees from some populations are morphologically similar to <i>P. tecunumanii&lt;/i&gt; , which adds to the confusion over the variety's geographic range. Recent field explorations have identified six new populations of supposed <i>P. patula&lt;/i&gt; var. &lt;i&gt;longipedunculata&lt;/i&gt; in the Sierra Madre del Sur of Oaxaca and Guerrero. In an effort to determine the validity of these sightings, botanical samples were collected from 79 trees in these six populations and were assessed for ten cone and needle morphology traits. Random Amplified Polymorphic DNA (RAPD) analyses were conducted on 73 trees from the six populations, 38 of which were in common to 79 trees used in the botanical study. Species control lots for both the botanical and RAPD studies were <i>P. herrerae</i>, <i>P. oocarpa</i>, <i>P. patula</i>, <i>P. pringlei&lt;/i&gt; and <i>P. tecunumanii</i>. Morphologic assessment indicated trees in the Manzanal population were predominantly &lt;i&gt;patula&lt;/i&gt; -related, but trees in the other five populations grouped into two clusters that were significantly different from <i>P. patula&lt;/i&gt; and <i>P. tecunumanii&lt;/i&gt; and not strongly related to the other control species. Conversely, molecular marker results indicated that four of the populations, Manzanal, San Mateo, Tlacuache (Oaxaca) and Yextla (Guerrero) were genetically indistinguishable or closely related to <i>P. patula</i>. The remaining two populations, Juquila (Oaxaca) and Palo Blanco (Guerrero), were closely related genetically to <i>P. herrerae / P. pringlei</i>. The morphologic study indicated that 5% of the trees in the six populations were indistinguishable from <i>P. tecunumanii</i>, but marker analyses indicated that the trees in question were of either <i>P. patula&lt;/i&gt; or <i>P. herrerae / P. pringlei&lt;/i&gt; origin. <i>Pinus tecunumanii&lt;/i&gt; does not appear to occur in the Sierra Madre del Sur of Oaxaca and Guerrero, but a four-needle type of <i>P. herrerae&lt;/i&gt; that can be very easily confused with <i>P. patula&lt;/i&gt; var. &lt;i&gt;longipedunculata&lt;/i&gt; does. The geographic range of <i>P. patula&lt;/i&gt; var. &lt;i&gt;longipedunculata&lt;/i&gt; is defined as occurring from northeastern Oaxaca to central Guerrero. The existence of populations of the variety in Chiapas needs to be verified using molecular techniques. The genetic relationship between <i>P. pringlei&lt;/i&gt; and <i>P. herrerae&lt;/i&gt; is much closer than heretofore thought, even though the morphology of each species is very distinctive.

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