Source: http://2012.botanyconference.org/engine/search/index.php?func=detail&aid=772
Timestamp: 2019-04-26 05:03:47+00:00

Document:
The LEAFY gene illuminates species relationships, allopolyploid speciation and biogeography in the North American Viola canadensis (Violaceae) complex.
The Viola canadensis complex consists of nine stemmed species with white or purple corollas, distributed across North America (including northern Mexico). The group belongs to the heterogenous Northern Hemisphere Sect. Chamaemelanium with 35-45 diploid and polyploid species possessing a base chromosome number of x=6. The complex is represented by transcontinental forest-dwelling V. canadensis (n=12); similar but little known V. scopulorum (n=6 based on one count) in Rocky Mountain forests; alpine V. lithion on two Nevada and Utah mountaintops; V. frank-smithii in one northern Utah box canyon; V. flettii in Olympic Peninsula alpine meadows; V. cuneata in serpentine barrens of Oregon and northern California (once counted as n=6); V. ocellata under redwoods in southern coastal Oregon and California; and V. flagelliformis of rocky oak woodlands and V. galeanaensis on mountain summits, in central and northern Mexico, respectively. The complex appears ideal as a group to test hypotheses of peripheral isolates and other models of speciation, investigate polyploid evolution, and examine processes yielding dramatic ecological differentiation. Previous research by the author and collaborators using Internal Transcribed Spacer DNA sequences placed the three west coast endemics basal in the group, and the Mexican species sister to V. canadensis plus V. lithion, with the latter embedded among V. canadensis populations. Preliminary data from the LEAFY gene, directly sequenced from PCR products, corroborate the ITS relationships and further reveal numerous nucleotide polymorphisms in V.canadensis individuals across the range of the species. Sequences from V. flagelliformis in Mexico show corresponding polymorphisms at most of the same nucleotide positions as the V. canadensis sequences, suggesting the two are allopolyploids and may have a common ancestor. It is likely that the Intermountain V. frank-smithii and V. lithion, as well as Mexican V. galeanaensis, are similarly allopolyploid and derived from the same ancestor. Isolation and sequencing of LEAFY homoeologs in the putative allotetraploids, and sequencing of additional species and populations, are underway to clarify relationships and speciation processes in this interesting complex.

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