Article

The Eastern Asian and Eastern and Western North American Floristic Disjunction: Congruent Phylogenetic Patterns in Seven Diverse Genera

Department of Botany, Washington State University, Pullman, Washington, 99164-4238,
Molecular Phylogenetics and Evolution (Impact Factor: 4.02). 11/1998; 10(2):178-90. DOI: 10.1006/mpev.1998.0524
Source: PubMed

ABSTRACT One of the most remarkable examples of intercontinental disjunction of the North Temperate Flora involves eastern Asia and eastern and western North America. Although there has been considerable interest in this phytogeographic pattern for over 150 years (e.g., Gray, 1859; Li, 1952; Graham, 1972; Boufford and Spongberg, 1983; Wu, 1983; Tiffney, 1985a, 1985b), relationships among taxa displaying the disjunction remain obscure. Understanding phylogenetic relationships is, however, a prerequisite for historical biogeographic analyses of this distributional pattern. To understand better the relationships of taxa displaying this intercontinental disjunction, phylogenetic analyses were conducted using a variety of DNA data sets for species of four genera (Cornus, Boykinia, Tiarella, and Trautvetteria) that occur in eastern Asia, eastern North America, and western North America. An area cladogram was constructed for each of the four genera, all of which show a similar pattern of relationship: the eastern Asian species are sister to all North American species. An identical phylogenetic pattern is also found in three other taxa exhibiting this disjunction (Aralia sect. Aralia, Calycanthus, and Adiantum pedatum). The congruent phylogenetic pattern found in these seven diverse genera raises the possibility of a common origin of the eastern Asia, eastern and western North America disjunction. The data are in agreement with the long-standing hypothesis that this well-known floristic disjunction represents the fragmentation of a once continuous Mixed Mesophytic forest community and suggest that the disjunction may have involved only two major vicariance events: an initial split between Eurasia and North America, followed by the isolation of floras between eastern and western North America. However, congruence between phylogenies and geographic distributions does not necessarily indicate an identical phytogeographic history. Taxa exhibiting the same phylogenetic pattern may have originated at different geological times. Analysis of divergence times using the molecular clock indicates that species of Cornus, Boykinia, and Calycanthus may have diverged at different geological times, suggesting that the floristic disjunction involving eastern Asia and North America may not be simple; it may have involved multiple historical events at very different geological times in different genera.

Download full-text

Full-text

Available from: Douglas E Soltis, Sep 08, 2014
1 Follower
 · 
95 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abies, the second largest genus of Pinaceae, consists of approximately 48 species occurring in the north temperate region. Previous molecular phylogenetic studies improved our understanding of relationships within the genus, but were limited by relying on only DNA sequence data from single genome and low taxonomic sampling. Here we use DNA data from three genomes (sequences of internal transcribed spacer of nrITS, three chloroplast DNA intergenic spacers, and two mitochondrial intergenic spacers) from 42 species to elucidate species relationships and construct the biogeographic history of Abies. We further estimated the divergence times of intercontinental disjunction using a relaxed molecular clock calibrated with three macro-fossils. Our phylogenetic analyses recovered six robust clades largely consistent with previous classifications of sections. A sister relationship between the eastern Asian and Europe-Mediterranean clades was highly supported. The monophyly of section Balsamea, disjunct in Far East and western North America, is supported by the nrITS data but not by the cpDNA data. Discordance on placement of section Balsamea between the paternally inherited cpDNA and maternally inherited mtDNA trees was also observed. The data suggested that ancient hybridization was likely involved in the origin of sect. Balsamea. Results from biogeographic analyses and divergence time estimation suggested an origin and early diversification of Abies in an area of high latitude around the Pacific during the Eocene. The present disjunction in eastern Asia and Europe-Mediterranean area of Abies was likely the result of southward migration and isolation by the Turgai Strait in the Late Eocene. An ‘out-of-America’ migration, for the origin of an eastern Asian and western North American disjunct species pairs in section Amabilis was supported. The results suggested a western North American origin of the section with subsequent dispersal across the Bering Land Bridge (BLB) to Japan during the Middle Miocene.
    Molecular Phylogenetics and Evolution 01/2015; 82:1-14. DOI:10.1016/j.ympev.2014.10.008 · 4.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rhodiola L. (Crassulaceae) is a mid-sized plant genus consisting of about 70 species, with most species distributed on the Qinghai-Tibetan Plateau (QTP) and the adjacent areas, and several species in north-east Asia, Europe, and North America. This study explored the origin and diversification history of Rhodiola and tested the biogeographic relationships between the QTP and other regions of the Northern Hemisphere. We sequenced the nuclear ribosomal internal transcribed spacers and eight plastid DNA fragments representing 55 species of Rhodiola, and reconstructed phylogenetic relationships with maximum parsimony, maximum likelihood and Bayesian inference. Several instances of incongruence between the nuclear and the plastid data sets were revealed, which can best be explained by reticulate evolution. Species of Rhodiola and Pseudosedum form a well-supported clade sister to Phedimus. Dating analysis suggested that the origin and diversification times of this group are largely correlated with the extensive uplifts of the Qinghai-Tibetan Plateau. Ancestral state reconstruction supports the hypothesis that Rhodiola originated on the QTP, and then dispersed to other regions of the Northern Hemisphere. Our findings highlight the importance of the uplifts of the Qinghai-Tibetan Plateau in promoting species diversification and the possible role of reticulate evolution in the diversification process. Our results also suggest the biogeographic significance of QTP as the source area in alpine plant evolution in the Northern Hemisphere.
    Molecular Phylogenetics and Evolution 04/2014; 77. DOI:10.1016/j.ympev.2014.04.013 · 4.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 39, The diverse butterfly subtribe Euptychiina was thought to be restricted to the Americas. However, there is mounting evidence for the Oriental Palaeonympha opalina being part of Euptychiina and thus a disjunct distribution between it (in eastern Asia) and its sister taxon (in eastern North America). Such a disjunct distribution in both eastern Asia and eastern North America has never been reported for any butterfly taxon. We used 4447 bp of DNA sequences from one mitochondrial gene and four nuclear genes for 102 Euptychiina taxa to obtain a phylogenetic hypothesis of the subtribe, estimate dates of origin and diversifica- tion for major clades and perform a biogeographic analysis. Euptychiina originated 31 Ma in South America. Early Euptychiina dispersed from North to South America via the tem- porary connection known as GAARlandia during Eocene–Oligocene times. The current disjunct distribution of the Oriental Palaeonympha opalina is the result of a northbound dis- persal of a lineage from South America into eastern Asia via North America. The common ancestor of Palaeonympha and its sister taxon Megisto inhabited the continuous forest belt across North Asia and North America, which was connected by Beringia. The closure of this connection caused the split between Palaeonympha and Megisto around 13 Ma and the severe extinctions in western North America because of the climatic changes of the Late Miocene (from 13.5 Ma onwards) resulted in the classic ‘eastern Asia and eastern North America’ disjunct distribution.
    Zoologica Scripta 05/2013; 39:243-258. DOI:10.1111/j.1463-6409.2010.00421.x · 2.92 Impact Factor