GOULD, KATHERINE R.* AND MARK C. TEBBITT. Science Department, Brooklyn Botanic Garden, Brooklyn, NY 11225. - Morphological and molecular variation in Helianthemum dumosum (Cistaceae), a rare coastal heathland taxon, and its widespread relative, H. canadense.
The taxonomic status of Helianthemum dumosum, the rare and
endangered Bushy Rockrose, was investigated using morphological and
molecular methods. Helianthemum dumosum has a highly
restricted range, found mainly on coastal heathland habitat in
southern New England (especially Cape Cod, Nantucket, and Martha’s
Vineyard) and Long Island, NY. However, it is often confused with the
geographically widespread and sympatric close relative, H.
canadense, and morphological intermediates between the two have
been found. We searched for taxon-specific molecular markers and
evidence of hybridization and introgression between the two using the
high-resolution fingerprinting technique of intersimple sequence
repeats (ISSRs). We performed multivariate statistical analyses and a
comparative cladistic analysis between the ISSR data and morphological
data. Preliminary results indicate that a pattern of clinal variation
between the two taxa exists.
Key words: Cistaceae, coastal heathland, Helianthemum, ISSR, rare plant