Submitted to: Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2000
Publication Date: N/A
Interpretive Summary: The Amaryllis family (Amaryllidaceae) is an important family of valued ornamental flower bulbs including the daffodils (Narcissus), snowdrops & snowbells (Galanthus & Leucojum), hurricane lilies (Lycoris) & amaryllis (Hippeastrum). A sizeable number of genera of the family are found only on the American continents, & the relationships among them have never been understood. We obtained DNA sequences for a spacer region of the genes coding for ribosomal RNA from 76 species of American Amaryllidaceae (representing all but 4 of the American genera) & used the aligned DNA sequences to analyse their genetic relationships. The DNA sequences ITS resolve two distinct groups within the American genera, an Andean lineage with twice the typical number of chromosomes characteristic of the family, a primarily extra-Andean group ("hippeastroid": consisting of Hippeastrum & its closest relatives.). Within the hippeastroid group, the Brazilian genera Griffinia & Worsleya, both with blue flowers (a rare characteristic in the family) represent the oldest or most isolated lineage. However, the confidence statistics generated for our sequence-based family tree present the lingering possibility that these two genera (the tribe Griffinieae) may be ancestral to the entire American group. Our data indicate that some previous assumptions of relationship within the family are incorrect. This information will be useful to horticulturists interested in developing hybrids between closely related genera, and geneticists looking for useful genes for varietal improvement.
Technical Abstract: We obtained ITS rDNA sequences for 76 species of American Amaryllidaceae & analysed the aligned matrix cladistically, both with & without gaps included, using two species of Pancratium as outgroup. ITS resolves two moderately to strongly supported groups, an Andean tetraploid clade, & a primarily extra-Andean "hippeastroid" clade. Within the hippeastroid subclade, the tribe Griffineae is resolved as sister to the rest of Hippestreae. The genera Rhodophiala and Zephyranthes are resolved as polyphyletic, but the possibility of reticulation within this clade argues against any re-arrangement of these genera without further investigation. Within the Andean subclade, Eustephieae resolves as sister to all other tribes; a distinct petiolate-leafed group is resolved, combining the tribe Eucharideae & the petiolate Stenomesseae; and a distinct Hymenocallideae is supported. These Andean clades are all at least partially supported by plastid sequence data as well. We infer from our data that a great deal of the diversity of the family in the Americas is recent, & that the American Amaryllidaceae may have been reduced to peripheral isolates some time after its initial entry & spread through the Americas. While the sister relationship of the American and Eurasian clades might argue for a Boreotropical origin for the family in America, the cladistic relationships within the American clade based on ITS do not provide any further support for this or any other hypothesis of the family's entry into America.The new tribe Clinantheae is described (four genera: Clinanthus, Pamianthe, Paramongaia and Pucara), & the lorate-leafed species of Stenomesson are transferred to Clinanthus.