Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree

Abstract

Although the relationship of angiosperms to other seed plants remains controversial, great progress has been made in identifying the earliest extant splits in flowering-plant phylogeny, with the discovery that the New Caledonian shrub Amborella trichopoda, the water lilies (Nymphaeales), and the woody Austrobaileyales constitute a basal grade of lines that diverged before the main radiation in the clade. By focusing attention on these ancient lines, this finding has re-written our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy. The discovery of a new basal lineage would lead to further re-evaluation of the initial angiosperm radiation, but would also be unexpected, as nearly all of the approximately 460 flowering-plant families have been surveyed in molecular studies. Here we show that Hydatellaceae, a small family of dwarf aquatics that were formerly interpreted as monocots, are instead a highly modified and previously unrecognized ancient lineage of angiosperms. Molecular phylogenetic analyses of multiple plastid genes and associated noncoding regions from the two genera of Hydatellaceae identify this overlooked family as the sister group of Nymphaeales. This surprising result is further corroborated by evidence from the nuclear gene phytochrome C (PHYC), and by numerous morphological characters. This indicates that water lilies are part of a larger lineage that evolved more extreme and diverse modifications for life in an aquatic habitat than previously recognized.

Ancestral traits and specializations in the flowers of the basal grade of living angiosperms

“…-We have long been familiar with giant flowered waterlilies with numerous floral parts (Davis & al., 2008) and, since recently (Saarela & al., 2007), with the minute flowered, one parted Hydatellaceae, now considered to consist of the single genus Trithuria Hook.f. .…”

Integrating Early Cretaceous Fossils into the Phylogeny of Living Angiosperms: ANITA Lines and Relatives of Chloranthaceae

“…This data set was first presented in Doyle and Endress (2000), used with some modifications in Saarela et al (2007), and substantially revised with more taxa and characters in Endress and Doyle (2009) and Doyle and Endress (2010). Theoretically, the ideal approach might be a "total evidence" analysis of a matrix containing molecular and morphological data for living taxa but only morphology for fossils (Springer et al 2001;Hermsen and Hendricks 2008).…”

Revisiting Mayacaceae Kunth towards to future perspectives in the family

“…The idea of Mayacaceae be part of the xyrid clade has been sustained by different authors along the years (Linder e Rudall 2005;Saarela et al 2007;Givnish et al2010;Stevens 2014). Jansen & Bremer (2004) for example indicated that Mayacaceae is placed in the same clade along with Eriocaulaceae and Xyridaceae, ands as sister group of Hydatelaceae and Cyperaceae.…”

“…Jansen & Bremer (2004) for example indicated that Mayacaceae is placed in the same clade along with Eriocaulaceae and Xyridaceae, ands as sister group of Hydatelaceae and Cyperaceae. Despite the exclusion of Hydatelaceae from the Monocots (Saarela et al 2007), this analysis could be influenced, according to these authors, by the phenomenon of the long branch attraction (Jansen & Bremer 2004), which indicates that the molecular analysis could be affected by other factors depending on the sampling used.…”