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Key Laboratory for Plant Diversity and Biogeography of East Asia
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Location: Home > Key Laboratory for Plant Diversity and Biogeography of East Asia > NIE Zelong's Group > Professor Nie Zelong
Professor Nie Zelong
source:     author:     2013-09-17

Associate Professor of Botany

Major research has been focused on molecular systematics and intercontinental disjunctions of flowering plants in the Northern Hemisphere as well as cytogeography on the alpine flora and plants in the Hengduan Mountains and the Himalayan regions. Taxa studied related to molecular systematics and biogeographic disjunctions in the Northern Hemisphere include Symplocarpus and Lysichiton (Araceae), Sassafras (Lauraceae), Kelloggia, Mitchella and Paederia (Rubiaceae), Phryma (Phrymaceae), Toxicodendron (Anacardiaceae), Anaphalis (Asteraceae), Parthenocissus and Ampelopsis (Vitaceae), and Magnoliaceae. I have been conducting cytogeographic studies on the Hengduan Mountains, with the case study of Tibetia, Leontopodium, Anaphalis from this area.

Email: niezl@mail.kib.ac.cn 


Research Interests

1. Eastern Asian – North American Disjunction

      Intercontinental disjunction between eastern Asia and North America is one of the most well-known and complicate biogeographic patterns in the world. It has always been a hot-spot for biogeographic researches and attentions. More than 10 representative groups from species to family level were investigated, i.e., Phryma leptostachys, Anaphalis, Astilbe, Kelloggia, Parthenocissus, Maianthemum, Mitchella, Sassafras, Toxicodendron, Orontioideae, and Magnoliaceae, etc. Phylogenetic reconstruction, divergence time, and ancestral areas reconstruction were analyzed for understanding their biogeographic origin, diversification, and migration patterns.  

     Anaphalis: It is the largest Asian genus in the tribe Gnaphalieae (Asteraceae) and has its greatest species diversity in the eastern Himalayas. The nuclear internal and external transcribed spacers were sequenced for Anaphalis species, with an emphasis on the eastern Himalayan taxa to examine the monophyly and construct the phylogenetic relationships of and within the genus. The results suggest that all species of Anaphalis are nested with Helichrysum, showing a close relationship with a Mediterranean–Asian group of Helichrysum. Although the monophyly of Anaphalis is only weakly supported, two clades within the genus are well recognized, each consisting of two sub-groups. The inferred phylogenetic relationships within Anaphalis correspond to the shape of leaf base, rather than the morphology of the capitula and phyllaries that are usually used for species delimitation and classification in the genus. All four subgroups of Anaphalis are common and diversified in the eastern Himalayas with multiple dispersals out of this region. The sole North American species of Anaphalis is best hypothesized to be the result of long-distance dispersal or overland migration via Bering land bridge from Asia. Our analyses suggest that the extant distribution of Anaphalis has most likely resulted one radiation into the eastern Himalayas followed by repeated independent dispersals and/or radiations mostly into eastern Asia but also into the western Himalayas, North America, and southeast Asia (Nie et al., 2013).

      Parthenocissus: a genus of the grape family Vitaceae and has a disjunct distribution in Asia and North America with members in both tropical and temperate regions. The monophyly of Parthenocissus has not yet been tested, and the species relationships and the evolution of its intercontinental disjunction have not been investigated with extensive sampling and molecular phylogenetic methods. Plastid (trnL-F, rps16, and atpB-rbcL) and nuclear GAI1 sequences of 56 accessions representing all 12 Parthenocissus species were analyzed with parsimony, likelihood, and Bayesian inference. Parthenocissus is monophyletic and sister to the newly described segregate genus Yua. Two major clades within Parthenocissus are recognizable corresponding to their distribution in Asia and North America. The disjunction between the two continents is estimated to be at 21.64 (95% higher posterior densities 10.23–34.89) million years ago. Parthenocissus is likely to have derived from the Eocene boreotropical element. Its current Asian–North American disjunction is dated to the early Miocene, congruent with fossil and paleoclimatic evidence. The tropical species is nested within the temperate clade and is inferred to have dispersed from the adjacent temperate regions. Parthenocissus and Yua are best treated as distinct genera. Leaflet number in this genus has a complex history and cannot be used as a character for infrageneric classification (Nie et al., 2010).

     Toxicodendron: a genus in the Rhus complex of Anacardiaceae with a disjunct distribution between eastern Asia and North America, extending to southeastern Asia and the neotropics. Nuclear (internal transcribed spacer, external transcribed spacer, and NIA-i3) and chloroplast (ndhF and trnL-F) sequences were used to construct phylogenetic relationships of Toxicodendron. Phylogenetic analysis of these data strongly support Toxicodendron as a monophyletic group distinct from other genera of the Rhus complex, and the phylogeny does not fully corroborate classification at the sectional level. Two temperate disjunct lineages were detected, one from section Toxicodendron and the other between the eastern North American Toxicodendron vernix and the eastern Asian Toxicodendron vernicifluum. Their divergence times were estimated to be 13.46 (7.95–19.42) and 7.53 (2.76–12.86) mya, respectively. The disjunction between section Griffithii (taxa from warm temperate to tropical Asia) and Toxicodendron striatum (from the neotropics) was supported and their divergence time was estimated to be 20.84 (11.16–30.52) mya in the early Miocene. Our biogeographic results and the paleontological data support the Bering land bridge as the most likely route to explain the temperate disjunctions, yet the tropical disjunction in Toxicodendron seems to be best explained by the North Atlantic land bridge hypothesis (Nie et al., 2009).

      Mitchella: It is a small genus of the Rubiaceae with only two species. It is the only herbaceous semishrub of the family showing a disjunct distribution in eastern Asia and eastern North America, extending to Central America. Its phylogeny and biogeographical diversification remain poorly understood. In this study, we conducted phylogenetic and biogeographical analyses for Mitchella and its close relative Damnacanthus based on sequences of the nuclear internal transcribed spacer (ITS) and four plastid markers (rbcL, atpB-rbcL, rps16 and trnL-F). Mitchella is monophyletic, consisting of an eastern Asian M. undulata clade and a New World M. repens clade. Our results also support Mitchella as the closest relative to the eastern Asian Damnacanthus. The divergence time between the two intercontinental disjunct Mitchella species was dated to 7.73 Mya, with a 95% highest posterior density (HPD) of 3.14-12.53 Mya, using the Bayesian relaxed clock estimation. Ancestral area reconstructions suggest that the genus originated in eastern Asia. The semishrub Mitchella appears to have arisen from its woody ancestor in eastern Asia and then migrated to North America via the Bering land bridge in the late Miocene (Huang et al., 2013).

       Magnoliaceae: Three nuclear genes (PHYA, LFY, and GAI1) revealed that 12 major groups largely consistent with the recent taxonomic revision at the sectional and subsectional level. However, relationships at deeper nodes of the subfamily Magnolioideae remained poorly resolved, perhaps due to an early radiation of the subfamily. Bayesian dating suggested that a complicated divergent evolution of Magnolioideae began around the early Eocene (54.57mya), concordant with paleoclimatic and fossil evidence. Intercontinental disjunctions of Magnoliaceae in the Northern Hemisphere originated during at least two geologic periods. The more recent one occurred after the middle Miocene, producing two well-recognized temperate disjunct lineages between eastern Asia and eastern North America. The second may have occurred no later than the Oligocene, with ancient separations between or within tropical and relict temperate lineages (Nie et al., 2008).

       Our results supported the hypothesis that north temperate disjunctions were relicts of the Boretropical flora once widely distributed in the Northern Hemisphere. The disjunct pattern was formed in multiple times in the whole Tertiary, with migration more relatated to Beringia forboth temperate and pantropical taxa rather than North Atlantic land bridge. Herbs usually had a divergence time after middle Miocene, while those of woody taxa no later than the Miocene. North temperate disjuncts are also younger than pantropical ones. Long distance dispersal played a similar important role as varcariance. This study also suggested multiple origins of the eastern Asian flora, represented by both ancient Sino-Japanese and young Sino-Himalayan elements. In the Tertiary, large extinction had been occurred in the Northern Hemisphere. The complex disjunct pattern in eastern Asia – North America might directly lead to the complicate origin and source of Sino-Himalayan elements. Morphological stasis or convergence is common in disjunct taxa, which indicates a long stable and similar habitat among relitct floras in the Northern Hemisphere.


2. Global Biogeography

     Ampelopsis clade: The Ampelopsis and its close allies of the grape family Vitaceae contains ca. 43 species disjunctly distributed in Asia, Europe, North America, South America, Africa, and Australia, and is a rare example to study both the Northern and the Southern Hemisphere intercontinental disjunctions. We reconstruct the temporal and spatial diversification of the Ampelopsis clade to explore the evolutionary processes that have resulted in their intercontinental disjunctions in six continents. The Bayesian molecular clock dating and the likelihood ancestral area analyses suggest that the Ampelopsis clade most likely originated in North America with its crown group dated at 41.2 Ma (95% HPD 23.4 - 61.0 Ma) in the middle Eocene. Two independent Laurasian migrations into Eurasia are inferred to have occurred in the early Miocene via the North Atlantic land bridges. The ancestor of the Southern Hemisphere lineage migrated from North America to South America in the early Oligocene. The Gondwanan-like pattern of intercontinental disjunction is best explained by two long-distance dispersals: once from South America to Africa estimated at 30.5 Ma (95% HPD 16.9 - 45.9 Ma), and the other from South America to Australia dated to 19.2 Ma (95% HPD 6.7 - 22.3 Ma). The global disjunctions in the Ampelopsis clade are best explained by a diversification model of North American origin, two Laurasian migrations, one migration into South America, and two post-Gondwanan long-distance dispersals. These findings highlight the importance of both vicariance and long distance dispersal in shaping intercontinental disjunctions of flowering plants (Nie et al., 2012).

      Paederia: Pantropical intercontinental disjunction is a common biogeographical pattern in flowering plants exhibiting a discontinuous distribution primarily in tropical Asia, Africa and the Americas. Only a few plant groups with this pattern have been investigated at the generic level with molecular phylogenetic and biogeographical methods. Paederia (Rubiaceae) is a pantropical genus of 31 species of woody lianas, with the greatest species diversity in continental Asia and Madagascar and only two species from tropical America. The aim of this study was to reconstruct the biogeographical history of Paederia based on phylogenetic analyses to explore how the genus attained its pantropical distribution. Maximum parsimony and Bayesian inference were used for phylogenetic analyses using sequences of five plastid markers (the rbcL gene, rps16 intron, trnT-F region, atpB-rbcL spacer and psbA-trnH spacer). Biogeographical inferences were based on a Bayesian uncorrelated lognormal relaxed molecular clock together with both Bayesian and likelihood ancestral area reconstructions. The data suggest an early diverged Asian lineage sister to the clade of the remaining species consisting of a predominantly Asian sub-clade and a primarily Malagasy sub-clade. Paederia is inferred to have originated in the Oligocene in tropical continental Asia. It then reached Africa in the early to middle Miocene, most probably via long-distance dispersal across the Indian Ocean. The two Neotropical species are inferred to have derived independently in the late Miocene from ancestors of Asia and East Africa, respectively. The results demonstrate the importance of post-Boreotropical long-distance dispersals (across three major oceans) in shaping the global pantropical disjunction in some plants, such as Paederia, with small, winged diaspores adapted to long-distance dispersal by various agents including wind, ocean currents or birds. Overland migration is less likely to explain its palaeotropical disjunction between Asia and Africa (Nie et al., 2013).


3. Polyploidy in the Hengduan Moutains and Tibetan Plateau

      The Hengduan Mountain region is located at the eastern end of the Himalayan range and in the southeastern corner of the Qinghai-Tibet Plateau in eastern Asia. It is probably the richest temperate region in the world biologically, with about 8000 species recorded from the 500,000 km2 region. A high rate of polyploidy was expected in the Hengduan Mountains because of the unusually high species diversity and endemism, the widespread alpine environment in this region, and the importance of polyploidy in plant evolution. Chromosome numbers for 552 taxa of native Hengduan angiosperms were obtained from published literature. If the criterion of infrageneric polyploidy is used (i.e., the possession of three or more basic chromosome sets in a nucleus), the frequency of polyploidy is only 22%. It is 37% and 58% if taxa with haploid chromosome number n =14 or more, or n = 11 or more are considered to be polyploids, respectively. Several highly diversified groups such as Aconitum and Delphinium also show a low proportion of polyploidy (18.6% and 0%, respectively) in the Hengduan Mountains. Examples from other large plant groups (e.g., Saxifraga, Ligularia, and Cremanthodium) and endemic genera (e.g., Solms-laubachia, Tibetia, and Nomocharis) again indicated that polyploidy, especially infrageneric polyploidy, may have played a minor role in the evolutionary diversification of these plants in the Hengduan Mountains.

     However, there are many other cases that polyploidy is more frequent for plants in alpine areas of the eastern Himalayas and Hengduan Mountains region, such as Aconitum subgenus Lycoctonum, Buddleja, and Anaphalis. A diffuse pattern would be expected for chromosome evolution of plants from this region, but the problem is that which one (polyploidy or diploidy) has played relatively more important role. Comprehensive cytological data from a great number and diversity of plants from this region should be gathered for a better understanding of chromosomal evolution on a floristic level.




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