Eupatorium pilosum
Distinguishing Features: leaves are lance-ovate; major branches of inflorescence are often alternate.
Habitat: open areas, old fields and waste places.
Geographic Distribution : widespread in eastern U.S., mostly represented by polyploid apomicts.
Similar Species: Eupatorium rotundifolium (of which E. pilosum is often treated as a variety in floras) has leaves that are ovate in shape, and the major branches of the inflorescence are usually opposite.
Molecular Data : samples of E. pilosum (DNA #s 942, 1161, 2189, 2193, 2201, 2351, 2466, 2468) differ in ITS sequence from all other species by a minimum of 11 bp changes. This allows identification of E. pilosum as a progenitor of hybrids with E. sessilifolium (see linked pherogram), E. album, and E. semiserratum based on unique patterns of bp and indel polymorphisms.
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