A biosystematic study of Castilleja crista-galli (scrophulariaceae): An allopolyploid origin reexamined

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Castilleja crista-galli is confined to northwest Wyoming, south-central Montana, and central Idaho and displays morphological attributes typical of the omithophilous Indian-paintbrushes. We examined its putative allopolyploid origin with molecular, morphological, and cytological analyses. In analyses of restriction site mutations of the chloroplast genome, we found that none of the seventeen species of Castilleja examined was characterized by a unique haplotype or set of haplotypes. Rather, geographically isolated species are polymorphic for similar arrays of haplotypes. Moreover, we found no nuclear ribosomal DNA repeat types that characterized species; polymorphisms in nuclear ribosomal DNA repeats were distributed both among individuals and among repeat units of single individuals. Morphometric analyses revealed morphological discontinuities among species, including C. crista-galli, but cladistic analyses of morphological characters failed to reveal synapomorphies for most taxa. Thus, morphological and molecular data were uninformative regarding the hybrid origin of C. crista-galli. Results of cytological analyses do not support allopolyploid origin. We detected diploid and tetraploid populations of C. crista-galli, previously known as just an octoploid. We retain the specific status of C. crista-galli under a morphological species concept. We also suggest that the species of Castilleja included in this study may have radiated recently and rapidly, maintaining ancestral polymorphism.

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Systematic Botany

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