Species separation of Taxus baccata, T. canadensis, and T. cuspidata (Taxaceae) and origins of their reputed hybrids inferred from RAPD and cpDNA data

Species delimitation in Taxus (Taxaceae) has been controversial due to high levels of phenotypic plasticity. Reputed hybrids between species have been questioned due to the original crosses' accidental nature and the uncertainty regarding the parent species' distinctness. In this study 19...

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Bibliographic Details
Published in:American journal of botany 2003-02, Vol.90 (2), p.175-182
Main Authors: Collins, Dennis, Mill, Robert R., Möller, Michael
Format: Article
Language:English
Subjects:
Biological taxonomies
Botany
chloroplast inheritance
Chloroplasts
Classification
Coordinate systems
cpDNA
Deoxyribonucleic acid
DNA
Flowers & plants
Genetics
Genetics and Molecular Biology
Genotypes
hybrid origins
Hybridity
Plants
Polymerase chain reaction
RAPDs
Seedlings
Species
species separation
Taxa
Taxaceae
Taxus baccata
Taxus canadensis
Taxus cuspidata
Taxus × hunnewelliana
Taxus × media
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Summary:Species delimitation in Taxus (Taxaceae) has been controversial due to high levels of phenotypic plasticity. Reputed hybrids between species have been questioned due to the original crosses' accidental nature and the uncertainty regarding the parent species' distinctness. In this study 19 samples from three species (T. baccata, T. canadensis, T. cuspidata) and 31 from putative hybrids (T. x hunnewelliana, T. x media) have been DNA-fingerprinted using RAPDs and characterized for their respective chloroplast genotype using restriction digestions of polymerase chain reaction-(PCR) amplified trnL-F fragments. All samples showed unique RAPD banding profiles. Twenty-one RAPD bands were species-specific; the presence of these bands in the putative hybrids confirmed the hybrid origin and parentage suspected from morphological studies (T. cuspidata x T. canadensis = T x hunnewelliana, T. baccata x T. cuspidata = T. x media). Principal coordinates analysis (PCO) and unweighted pair-group method algorithm (UPGMA) analyses of RAPD bands clearly separated the species, indicating that they belong to discrete genetic stocks and supporting their individual species status. The two hybrid groups also clustered discretely. Chloroplast typing confirmed the direction of crosses. The data further suggested that repeated reciprocal crossings occurred in the production of the hybrid cultivars.
ISSN:0002-9122
1537-2197
DOI:10.3732/ajb.90.2.175