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United States Department of Agriculture

Agricultural Research Service

Research Project: CONSERVATION, CHARACTERIZATION, AND GENETIC IMPROVEMENT OF SUBTROPICAL AND TROPICAL ORNAMENTAL GERMPLASM

Location: Subtropical Horticulture Research

Title: Expanded nrDNA ITS/5.8S phylogeny for Amaryllidaceae tribe Hippeastreae (Asparagales)

Authors
item Garcia, Nicolas -
item Meerow, Alan
item Soltis, Pamela -
item Soltis, Douglas -

Submitted to: International Botanical Congress
Publication Type: Abstract Only
Publication Acceptance Date: April 14, 2011
Publication Date: N/A

Interpretive Summary: The Hippeastreae is an important American tribe of the amaryllis family containing several genera important in horticulture, such as Hippeastrum, Habranthus, Zephyranthes, Rhodophiala, and Sprekelia. Despite the long-standing interest in these plants, their taxonomy at the generic level has been controversial, with several segregates proposed during the last 40 years. A previous analysis of ribosomal DNA sequences indicated that the Rhodophiala, Habranthus, and Zephyranthes had multiple ancestry, but lacked good representation of Chilean-Argentinean groups, such as Famatina, Phycella, Placea, Rhodolirium, and Traubia. We have expanded the taxon sampling for this data set by including members of the Chilean endemic genera and additional species of Habranthus, Rhodophiala, Rhodolirium, Sprekelia, and Zephyranthes. The tribe comprises two major groups: a) Traubia, Placea, Phycella, Rhodolirium, and Famatina maulensis, characterized by x = 8 chromosomes, lack of polyploidy, and a capitate stigma, and b) Rhodophiala, Habranthus, Hippeastrum, Sprekelia, Zephyranthes, and the remainder of Famatina, characterized by several basic chromosome numbers ranging between x = 6 – 11, with frequent polyploidy. No clear morphological features diagnose the latter group. We are currently working with low-copy nuclear genes and several chloroplast regions to test further this phylogenetic hypothesis. This framework will serve as a basis for a phylogenetic classification of the group and study of its chromosomal evolution.

Technical Abstract: The Hippeastreae represent a subclade within the American clade of the cosmopolitan Amaryllidaceae s.s. and contain several species relevant for horticulture, such as Hippeastrum spp., Habranthus spp., Zephyranthes spp., Rhodophiala bifida, and Sprekelia formosissima. Despite the long-standing interest in these plants, their taxonomy at the generic level has been controversial, with several segregates proposed during the last 40 years. A previous phylogenetic analysis of the nrDNA ITS/5.8S region showed that certain genera are not monophyletic, such as Rhodophiala, Habranthus, and Zephyranthes, but lacked good representation of Chilean-Argentinean groups, such as Famatina, Phycella, Placea, Rhodolirium, and Traubia. The hypothesis of possible early lineage reticulation in the group was suggested. We have expanded the taxon sampling for this data set by including members of the Chilean endemic genera and additional species of Habranthus, Rhodophiala, Rhodolirium, Sprekelia, and Zephyranthes. A total of approximately 110 species correponds to more than 60% of the tribe's species-level diversity. The tribe comprises two major clades: a) Traubia, Placea, Phycella, Rhodolirium, and Famatina maulensis, characterized by x = 8, lack of polyploidy, and a capitate stigma, and b) Rhodophiala, Habranthus, Hippeastrum, Sprekelia, Zephyranthes, and the remainder of Famatina, characterized by several basic chromosome numbers ranging between x = 6 – 11, and frequent polyploidy and aneuploidy. No clear morphological features diagnose the latter clade. The first group appears to be composed of three main subclades: 1) Rhodolirium laetum and Traubia modesta, 2) Rhodolirium montanum, and 3) Phycella spp., Placea spp., Rhodolirium speciosum, and Famatina maulensis. The other major clade appears to be composed of four lineages with unresolved relationships: 1) Rhodophiala bifida, 2) Hippeastrum spp., 3) Eithea blumenavia, Chilean-Andean Rhodophiala spp., remaining Famatina spp., and South American-Caribbean-southeastern US Zephyranthes spp., and 4) South American-Mexican-southwestern US-Texan Zephyranthes spp., Habranthus spp., Sprekelia spp., and Haylockia americana. Certain species within Hippeastrum, Rhodophiala, Placea, and Phycella have identical or almost identical sequences to others, implying a sort of interspecific nrDNA concerted evolution and/or perhaps rapid radiations within these groups. We are currently working with low-copy nuclear genes and several chloroplast regions to test further this phylogenetic hypothesis; therefore the ITS/5.8S topology is only a first step towards an integrated phylogeny of the clade. This framework will serve as a basis for a phylogenetic classification of the group, study of its chromosomal evolution, and a test of the ancient inter-clade reticulation hypothesis in Hippeastreae.

Last Modified: 7/31/2014
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