Molecular phylogeography and species distribution modelling evidence of 'oceanic' adaptation for Actinidia eriantha with a refugium along the oceanic-continental gradient in a biodiversity hotspot.

BACKGROUND: Refugia is considered to be critical for maintaining biodiversity; while discerning the type and pattern of refugia is pivotal for our understanding of evolutionary processes in the context of conservation. Interglacial and glacial refugia have been studied throughout subtropical China. However, studies on refugia along the oceanic-continental gradient have largely been ignored. We used a liana Actinidia eriantha, which occurs across the eastern moist evergreen broad-leaved forests of subtropical China, as a case study to test hypotheses of refugia along the oceanic-continental gradient and 'oceanic' adaptation. RESULTS: The phylogeographic pattern of A. eriantha was explored using a combination of three cpDNA markers and 38 nuclear microsatellite loci, Species distribution modelling and dispersal corridors analysis. Our data showed intermediate levels of genetic diversity [haplotype diversity (hT) = 0.498; unbiased expected heterozygosity (UHE) = 0.510] both at the species and population level. Microsatellite loci revealed five clusters largely corresponding to geographic regions. Coalescent time of cpDNA lineages was dated to the middle Pliocene (ca. 4.03 Ma). Both geographic distance and climate difference have important roles for intraspecific divergence of the species. The Zhejiang-Fujian Hilly Region was demonstrated to be a refugium along the oceanic-continental gradient of the species and fit the 'refugia in refugia' pattern. Species distribution modelling analysis indicated that Precipitation of Coldest Quarter (importance of 44%), Temperature Seasonality (29%) and Mean Temperature of Wettest Quarter (25%) contributed the most to model development. By checking the isolines in the three climate layers, we found that A. eriantha prefer higher precipitation during the coldest quarter, lower seasonal temperature difference and lower mean temperature during the wettest quarter, which correspond to 'oceanic' adaptation. Actinidia eriantha expanded to its western distribution range along the dispersal corridor repeatedly during the glacial periods. CONCLUSIONS: Overall, our results provide integrated evidence demonstrating that the Zhejiang-Fujian Hilly Region is a refugium along the oceanic-continental gradient of Actinidia eriantha in subtropical China and that speciation is attributed to 'oceanic' adaptation. This study gives a deeper understanding of the refugia in subtropical China and will contribute to the conservation and utilization of kiwifruit wild resources in the context of climate change.

Primula sunhangii (Primulaceae): a new species from Hubei, Central China.

This report provides a description of Primula sunhangii from the Shennongjia Forestry District, Hubei Province in Central China, which is categorized as a new species of the primrose family. Primula sunhangii is morphologically similar to P. involucrata Wall. ex Duby in terms of its simple umbel, efarinose, and prolonged bracts. However, P. sunhangii is distinguished by its glabrous sepal, short petiole (compare with blade) and cylindrical calyx and capsule. Molecular phylogenetic analysis based on nuclear and cpDNA genes demonstrates that P. sunhangii and P. involucrata are closely related. Combining genetic and morphological data, the recognition of P. sunhangii as a unique new species is supported.

Geum sunhangii (Rosaceae), a new species from Hubei Province, China.

Geum sunhangii - first discovered in Shennongjia National Nature Reserve, Hubei Province, China - is described as a new species of Rosaceae. Compared to all known Chinese Geum species, the new species differs by possessing jointed styles, imbricate petals and a reniform radical leaf terminal leaflet. Most significantly, the jointed style is curved at an obtuse or a right angle. In addition, the inclusion of this species within the genus Geum was supported by phylogenetic analysis using the sequence data of a nuclear ribosomal internal transcribed spacer (nrITS) and a chloroplast trnL-trnF intergenic spacer. The new species was found to be closely related to G. rivale and G. aleppicum.

Silene sunhangii (Caryophyllaceae), a new species from China.

Silene sunhangii, a new species of Caryophyllaceae known from only three populations in Hubei and Hunan provinces of central China, is described. Both morphological and molecular data were used to assess the taxonomic status and relationships of this species. Morphologically, S. sunhangii is most similar to S. platyphylla Franch. from which it differs most readily in having 3-veined elliptical leaves without pubescence, tasseled catacorolla, pale purple to red petals without a linear lobe or narrow tooth and lanceolate, bifid to one third. A phylogenetic analysis based on nuclear ITS region identified the new species as a well-supported, independent lineage. Our new species is nested within a grade that encompasses species representing a polyphyletic Silene sect. Physolychnis (Benth.) Bocquet. Both the genetic and morphological data support the recognition of Silene sunhangii as a distinct species, although there is inconsistency between these two datasets as to the relationships of the new species.

Molecular Phylogeography and Ecological Niche Modeling of Sibbaldia procumbens s.l. (Rosaceae).

The phylogeographical analysis and ecological niche modeling (ENM) of the widely distributed Northern Hemisphere Sibbaldia procumbens s.l. can help evaluate how tectonic motion and climate change helped shape the current distribution patterns of this species. Three chloroplast regions (the atpI-atpH and trnL-trnF intergenic spacers and the trnL intron) were obtained from 332 (156 from present study and 176 from the previous study) individuals of S. procumbens s.l. An unrooted haplotype network was constructed using the software NETWORK, while BEAST was used to estimate the divergence times among haplotypes. ENM was performed by MAXENT to explore the historical dynamic distribution of S. procumbens s.l. The haplotype distribution demonstrates significant phylogeographical structure (N ST > G ST; P < 0.01). The best partitioning of genetic diversity by SAMOVA produced three groups, while the time to the most recent common ancestor of all haplotypes was estimated to originate during the Miocene, with most of the haplotype diversity having occurred during the Quaternary. The MAXENT analysis showed S. procumbens s.l. had a wider distribution range during the last glacial maximum and a narrower distribution range during the last interglacial, with predictions into the future showing the distribution range of S. procumbens s.l. shrinking.

Complete plastome sequencing from Toona (Meliaceae) and phylogenomic analyses within Sapindales.

PREMISE OF THE STUDY: Toona (Meliaceae, Sapindales) is a small genus of five species of trees native from southern and eastern Asia to New Guinea and Australia. Complete plastomes were sequenced for three Toona species to provide a basis for future plastome genetic studies in threatened species of Toona. In addition, plastome structural evolution and phylogenetic relationships across Sapindales were explored with a larger data set of 29 Sapindales plastomes (including members of six out of nine families). METHODS: The plastomes were determined using the Illumina sequencing platform; the phylogenetic analyses were conducted using maximum likelihood by RAxML. RESULTS: The lengths of three Toona plastomes range from 159,185 to 158,196 bp. A total of 113 unique genes were found in each plastome. Across Sapindales, plastome gene structure and content were largely conserved, with the exception of the contraction of the inverted repeat region to exclude ycf1 in some species of Rutaceae and Sapindaceae, and the movement of trnI-GAU and trnA-UGC to a position outside the inverted repeat region in some Rutaceae species. DISCUSSION: The three Toona plastomes possess the typical structure of angiosperm plastomes. Phylogenomic analysis of Sapindales recovered a mostly strongly supported phylogeny of Sapindales, including most of the backbone relationships, with some improvements compared to previous targeted-gene analyses.

Complete plastid genome sequencing of Trochodendraceae reveals a significant expansion of the inverted repeat and suggests a Paleogene divergence between the two extant species.

The early-diverging eudicot order Trochodendrales contains only two monospecific genera, Tetracentron and Trochodendron. Although an extensive fossil record indicates that the clade is perhaps 100 million years old and was widespread throughout the Northern Hemisphere during the Paleogene and Neogene, the two extant genera are both narrowly distributed in eastern Asia. Recent phylogenetic analyses strongly support a clade of Trochodendrales, Buxales, and Gunneridae (core eudicots), but complete plastome analyses do not resolve the relationships among these groups with strong support. However, plastid phylogenomic analyses have not included data for Tetracentron. To better resolve basal eudicot relationships and to clarify when the two extant genera of Trochodendrales diverged, we sequenced the complete plastid genome of Tetracentron sinense using Illumina technology. The Tetracentron and Trochodendron plastomes possess the typical gene content and arrangement that characterize most angiosperm plastid genomes, but both genomes have the same unusual ∼4 kb expansion of the inverted repeat region to include five genes (rpl22, rps3, rpl16, rpl14, and rps8) that are normally found in the large single-copy region. Maximum likelihood analyses of an 83-gene, 88 taxon angiosperm data set yield an identical tree topology as previous plastid-based trees, and moderately support the sister relationship between Buxaceae and Gunneridae. Molecular dating analyses suggest that Tetracentron and Trochodendron diverged between 44-30 million years ago, which is congruent with the fossil record of Trochodendrales and with previous estimates of the divergence time of these two taxa. We also characterize 154 simple sequence repeat loci from the Tetracentron sinense and Trochodendron aralioides plastomes that will be useful in future studies of population genetic structure for these relict species, both of which are of conservation concern.

Population genetic structure of two Medicago species shaped by distinct life form, mating system and seed dispersal.

BACKGROUND AND AIMS: Life form, mating system and seed dispersal are important adaptive traits of plants. In the first effort to characterize in detail the population genetic structure and dynamics of wild Medicago species in China, a population genetic study of two closely related Medicago species, M. lupulina and M. ruthenica, that are distinct in these traits, are reported. These species are valuable germplasm resources for the improvement of Medicago forage crops but are under threat of habitat destruction. METHODS: Three hundred and twenty-eight individuals from 16 populations of the annual species, M. lupulina, and 447 individuals from 15 populations of the perennial species, M. ruthenica, were studied using 15 and 17 microsatellite loci, respectively. Conventional and Bayesian-clustering analyses were utilized to estimate population genetic structure, mating system and gene flow. KEY RESULTS: Genetic diversity of M. lupulina (mean H(E)=0.246) was lower than that of M. ruthenica (mean H(E)=0.677). Populations of M. lupulina were more highly differentiated (F(ST)=0.535) than those of M. ruthenica (F(ST)=0.130). For M. lupulina, 55.5% of the genetic variation was partitioned among populations, whereas 76.6% of the variation existed within populations of M. ruthenica. Based on the genetic data, the selfing rates of M. lupulina and M. ruthenica were estimated at 95.8% and 29.5%, respectively. The genetic differentiation among populations of both species was positively correlated with geographical distance. CONCLUSIONS: The mating system differentiation estimated from the genetic data is consistent with floral morphology and observed pollinator visitation. There was a much higher historical gene flow in M. ruthenica than in M. lupulina, despite more effective seed dispersal mechanisms in M. lupulina. The population genetic structure and geographical distribution of the two Medicago species have been shaped by life form, mating systems and seed dispersal mechanisms.