The fern genus Tectaria has generally been placed in the family Tectariaceae or in subfamily Tectarioideae (placed in Dennstaedtiaceae, Dryopteridaceae or Polypodiaceae), both of which have been variously circumscribed in the past. Here we study for the first time the phylogenetic relationships of the associated genera Hypoderris (endemic to the Caribbean), Cionidium (endemic to New Caledonia) and Pseudotectaria (endemic to Madagascar and Comoros) using DNA sequence data. Based on a broad sampling of 72 species of eupolypods I (= Polypodiaceae sensu lato) and three plastid DNA regions (atpA, rbcL and the trnL-F intergenic spacer) we were able to place the three previously unsampled genera. Our results show that Cionidium, like Ctenitopsis, Fadyenia, Hemigramma and Quercifilix, is embedded in Tectaria, and the monophyly of Tectaria is therefore corroborated only if these segregate genera are included. Hypoderris is sister to Tectaria brauniana and together they are sister to Triplophyllum, which was found to be monophyletic. Despite their morphological similarity with Tectaria, the genera Pleocnemia and Pseudotectaria were placed in Dryopteridoideae. Polypodiaceae subfamily Tectarioideae (former family Tectariaceae) is hereby defined to include Arthropteris, Hypoderris, Pteridrys, Tectaria and Triplophyllum. Aenigmopteris may also belong here, but this genus remains unsampled.

Hainan, the second largest island of China, has the most extensive and best preserved tropical forests of this country. A network of 68 protected areas (54 of them are terrestrial) provides in situ conservation for the unique ecosystems of the island. We: (1) discuss an updated check-list of seed-plant species that are endemic to Hainan, (2) evaluate the extent to which the endemic flora has been the subject of molecular studies, and (3) investigate the conservation status of these species. We recognize 397 endemic species on the island, 271 of which are reported in the protected areas, and 144 of which have been Red-Listed (85 assigned to the Critically Endangered (40) or Endangered (45) IUCN categories). The families with the highest number of endemics are Rubiaceae (33 species), Lauraceae (27 species), and Poaceae (26 species). The island has only seven endemic genera, all of which are unispecific. Compared with other tropical islands, Hainan has a low number of endemics but our preliminary observations suggest that the island has a highly disharmonic flora when compared with that from the mainland. Nevertheless, most of the major clades of the seed-plant tree of life with representatives in China also have endemic species on the island. We argue that the low levels of endemism reflect the continental nature of Hainan and the fact that several areas of the island have not been fully inventoried. We were unable to find a single molecular systematic study focusing exclusively on the Hainan endemics; however, 24 of the endemic species have been included in phylogenetic studies targeting particular genera or families. Future research/conservation actions for the endemic flora of Hainan should focus in developing: (1) a red-list that assesses all 397 endemic species, (2) comprehensive floristic studies for the protected areas, (3) molecular phylogenetic and conservation genetic studies with a primary focus on the endemics, (4) studies to understand what ecological interactions are important in the biology of the endemic species, and (5) eco-geographical studies to identify Important Biodiversity Zones of endemism within Hainan and therefore potential new protected areas.

Whole-genome duplications (WGDs) are widespread in plants and frequently coincide with global climatic change events, such as the Cretaceous–Tertiary (KT) extinction event approximately 65 million years ago (mya). Ferns have larger genomes and higher chromosome numbers than seed plants, which likely resulted from multiple rounds of polyploidy. Here, we use diploid and triploid material from a model fern species, Ceratopteris thalictroides, for the detection of WGDs. High-quality RNA-seq data was used to infer the number of synonymous substitutions per synonymous site (Ks) between paralogs; Ks age distribution and absolute dating approach were used to determine the age of WGD events. Evidence of an ancient WGD event with a Ks peak value of approximately 1.2 was obtained for both samples; however, the Ks frequency distributions varied significantly. Importantly, we dated the WGD event at 51–53 mya, which coincides with the Paleocene-Eocene Thermal Maximum (PETM), when the Earth became warmer and wetter than any other period during the Cenozoic. Duplicate genes were preferentially retained for specific functions, such as environment response, further support that the duplicates may have promoted quick adaption to environmental changes and potentially resulted in evolutionary success, especially for pantropical species, such as C. thalictroides, which exhibits higher temperature tolerance.

Global conservation of plant biodiversity on tropical islands is a major priority, as approximately one third of all endangered plant species are insular endemics. Checklists can be an important first step in determining conservation priorities on islands. Hainan, the largest island in the Indo-Burma Biodiversity Hotspot, and therefore an international focus for conservation, has the most extensive and best preserved tropical forests in China. In this study we enumerate the endemic seed plants of Hainan Island. The checklist was prepared by consulting:(1) several bibliographic/taxonomic data base resources, (2) relevant taxonomic treatments and floras, and (3) plant taxonomists who are actively working with Chinese plants. The checklist also contains information concerning conservation status, the occurrence of Hainan endemics in four protected areas on the island, and available molecular phylogenies. An additional checklist of the species that were until recently thought to be endemic to Hainan, but are no longer considered to be, is also presented. In a separate paper in this issue of Botanical Review the patterns of endemism on Hainan Island are discussed.

Phytoremediation is a potentially suitable technology for taking up large amounts of N and P during plant growth and the removal of plant material, thereby avoiding eutrophication. We compared the capacity of nine different aquatic plant species for removing total P (TP), total N (TN), and NH4+-N from raw domestic sewage wastewater collected from a living area located in Guangzhou city, China, and different concentrations of artificial wastewater. The experiments were performed in two stages, namely screening and modification. In the screening stage, four plant species were identified from the nine grown in raw domestic sewage water for 36 days. In the modification stage, the TN and TP removal ability of different plant combinations were determined in artificial wastewater at different N/P concentrations. After having been grown in monocultures for 46 days, Ipomoea aquatica (90.6% and 8.8%) and Salvinia natans (67.3% and 14.2%) obtained the highest TP removal efficiency in lightly and highly polluted wastewater, respectively. The combination of S. natans and Eleocharis plantagineiformis effectively removed TP and TN from lightly polluted water, suggesting that this combination is suitable for phytoremediation of eutrophic wastewater.

No abstract

Diversification between islands and ecological radiation within islands are postulated to have occurred in the Euphorbia species (sect. Aphyllis subsect. Macaronesicae) on the Canary Islands. In this study, the biogeographical pattern of 11 species of subsect. Macaronesicae and the genetic differentiation among five species were investigated to distinguish the potential mode and mechanism of diversification and speciation. The biogeographical patterns and genetic structure were examined using statistical dispersal-vicariance analysis, Bayesian phylogenetic analysis, reduced median-joining haplotype network analysis, and discriminant analysis of principal components. The gene flow between related species was evaluated with an isolation-with-migration model. The ancestral range of the species of subsect. Macaronesicae was inferred to be Tenerife and the Cape Verde Islands, and Tenerife-La Gomera acted as sources of diversity to other islands of the Canary Islands. Inter-island colonization of E. lamarckii among the western islands and a colonization of E. regis-jubae from Gran Canaria to northern Africa were revealed. Both diversification between islands and radiation within islands have been revealed in the Euphorbia species (sect. Aphyllis subsect. Macaronesicae) of the Canary Islands. It was clear that this group began the speciation process in Tenerife-La Gomera, and this process occurred with gene flow between some related species.

BackgroundThere are different opinions about the relationship of two disjunctively distributed varieties Adiantum reniforme L. var. sinense Y.X.Lin and Adiantum reniforme L. Adiantum reniforme var. sinense is an endangered fern only distributed in a narrowed region of Chongqing city in China, while Adiantum reniforme var. reniforme just distributed in Canary Islands and Madeira off the north-western African coast. To verify the relationship of these two taxa, relative phylogenetic analyses, karyotype analyses, microscopic spore observations and morphological studies were performed in this study. Besides, divergence time between A. reniforme var. sinense and A. reniforme var. reniforme was estimated using GTR model according to a phylogeny tree constructed with the three cpDNA markers atpA, atpB, and rbcL.ResultsPhylogenetic results and divergence time analyses--all individuals of A. reniforme var. sinense from 4 different populations (representing all biogeographic distributions) were clustered into one clade and all individuals of A. reniforme var. reniforme from 7 different populations (all biogeographic distributions are included) were clustered into another clade. The divergence between A. reniforme var. reniforme and A. reniforme var. sinense was estimated to be 4.94 (2.26-8.66) Myr. Based on karyotype analyses, A. reniforme var. reniforme was deduced to be hexaploidy with 2n = 180, X = 30, while A. reniforme var. sinense was known as tetraploidy. Microscopic spore observations suggested that surface ornamentation of A. reniforme var. reniforme is psilate, but that of A. reniforme var. sinense is rugate. Leaf blades of A. reniforme var. sinense are membranous and reniform and with several obvious concentric rings, and leaves of A. reniforme var. reniforme are pachyphyllous and coriaceous and are much rounder and similar to palm.ConclusionAdiantum reniforme var. sinense is an independent species rather than the variety of Adiantum reniforme var. reniforme. As a result, we approve Adiantum nelumboides X. C. Zhang, nom. & stat. nov. as a legal name instead of the former Adiantum reniforme var. sinense. China was determined to be the most probable evolution centre based on the results of phylogenetic analyses, divergence estimation, relative palaeogeography and palaeoclimate materials.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0361-9) contains supplementary material, which is available to authorized users.