Testing Deep Reticulate Evolution in Amaryllidaceae Tribe Hippeastreae (Asparagales) with ITS and Chloroplast Sequence Data

Abstract—

The phylogeny of Amaryllidaceae tribe Hippeastreae was inferred using chloroplast (3′ ycf1, ndhF, trnL ^(UAA)-F ^(GAA)) and nuclear (ITS rDNA) sequence data under maximum parsimony and maximum likelihood frameworks. Network analyses were applied to resolve conflicting signals among data sets and putative scenarios of reticulate evolution. All analyses of all regions consistently revealed two major clades, which are formalized as subtribes: A) Traubiinae, formed by Traubia, Placea, Phycella, Rhodolirium, and Famatina maulensis, characterized by x = 8, rare polyploidy, and a capitate stigma, and B) Hippeastrinae, including Eithea, Habranthus, Haylockia, Hippeastrum, Rhodophiala, Sprekelia, Zephyranthes, and Famatina pro parte, characterized by a range of basic chromosome numbers (x = 6‐11) and frequent polyploidy and aneuploidy. No clear morphological features diagnose the latter clade, which contains ca. 90% of the tribe's species diversity. Our phylogenetic results question the monophyly of all genera in the tribe and show widespread cytonuclear discordance within the mainly Neotropical Hippeastrinae, further supporting putative ancient hybridization(s) preceding the radiation of this major clade. In contrast, the Traubiinae, endemic to Chile and Argentina, show a tree-like pattern of evolution, consistent with the apparent absence of allopolyploidy in this clade. A brief description, circumscription, and geographic distribution are provided for each subtribe.