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Chloroplast diversity in a putative hybrid swarm of Ponderosae (Pinaceae)
Author(s) -
Epperson Bryan K.,
Telewski Frank W.,
Willyard Ann
Publication year - 2009
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.0800005
Subject(s) - biology , taxon , pinaceae , disjunct , introgression , chloroplast dna , dendroctonus , hybrid , evolutionary biology , botany , genus , phylogenetics , population , genetics , pinus <genus> , twig , demography , sociology , bark beetle , gene
The Ponderosae subsection of the genus Pinus contains numerous taxa in disjunct mountain ranges of southern Arizona and New Mexico, differing for several leaf and cone traits, key among which is the number of leaf needles per fascicle. Trees with three needles are often found together with trees having five needles and mixed numbers. One taxonomic hypothesis is that there are swarms of hybrids between P. ponderosa and P. arizonica . A second hypothesis is that there are spatial mixtures of two separate taxa, five‐needle P. arizonica and a “taxon X” containing three needle and mixed needle trees. We genotyped chloroplasts in one putative hybrid swarm on Mt. Lemmon using microsatellite markers and show that cpDNA is almost completely differentiated between two separate morphotypes corresponding to P. arizonica and “taxon X.” Little if any introgression has occurred on Mt. Lemmon, and the simplest explanation is that little or no effective hybridization has occurred. Further results indicate that not only is taxon X not of hybrid origin, it is more closely related to nonregional Ponderosae other than P. ponderosa and P. arizonica . The results further suggest that other putative hybrid swarms in the region are also spatial mixtures of distinct taxa.