Abstract
Heloniadeae (Melanthiaceae) presents an East Asia–North America disjunct distribution. Different molecular and morphological data nevertheless support the tribe as a monophyletic group. However, their phylogenetic relationships and biogeographic history, together with the character evolution, are not clear. Therefore, we constructed a Bayesian phylogenetic tree for Heloniadeae using cpDNA and inferred the historical biogeography and floral character evolution. The results revealed that Heloniadeae was distributed in high-latitudes of East Asia and North America, originating since 22.2 mya. The East Asia clade migrated into southwest China, and subsequently colonized the Korean Peninsula, Taiwan, the Ryukyus, and spread northward to Japan and southern Sakhalin. The evolution of the inflorescence and number of flowers were phylogenetically conserved, associated with the historical biogeography of Heloniadeae. The inflorescences transferred from raceme to sub-umbel, and the number of flowers decreased during the dispersal process, which may be accompanied by changes in the breeding system. Besides, the anthesis period was more affected by the habitat environment than phylogenetic constraints. The flowering temperature of Heloniadeae was below 20 °C in most species, except H. kawanoi. Such a low temperature might not be conductive to pollinator activities, but it could be compensated by sustaining seed production with long-lasting flowers.
Highlights
Disjunct distribution is a discontinuous distribution pattern of organisms, and many types of disjunct distributions have been reported[1,2]
Based on these previous morphological and molecular findings, this study aims to reconstruct the historical biogeography of Heloniadeae from a phylogenetic perspective, focusing on the origin and spreading of Heloniopsis, by the modelbased Bayesian evolutionary analysis
With Chionographis (C. chinensis and C. japonica) and Chamaelirium luteum as the outgroups, the phylogenetic tree confirms the monophyly of Heloniadeae that comprises a total of 11 taxa and one putative species from Taiwan (Fig. 1)
Summary
Disjunct distribution is a discontinuous distribution pattern of organisms, and many types of disjunct distributions have been reported[1,2]. (Helonias was abbreviated as He after here) distributed in eastern North America[27]; in contrast, Heloniopsis has five species distributed in China, Japan, Korea, and T aiwan[28]; Ypsilandra has five species in China and the H imalayas[28] These genera have perennial herbs with rosette leaves, scapose inflorescences, tepals with various colors, and seeds with caudate appendages on both ends. The stamen of Ypsilandra is free from the tepals, and the anther is basifixed with one locule These studies have provided a wealth of data for the morphology and phylogeny of these genera, showing some trends in distribution and flower characteristics. A hypothesis of the disjunct distribution was proposed, and the reconstruction of ancestral state and trait evolution, especially the floral parts, were explored in this study
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