Molecular phylogenetics and historical biogeography of Hawaiian Dryopteris (Dryopteridaceae)

The fern genus Dryopteris (Dryopteridaceae) is represented in the Hawaiian Islands by 18 endemic taxa and one non-endemic, native species. The goals of this study were to determine whether Dryopteris in Hawai'i is monophyletic and to infer the biogeographical origins of Hawaiian Dryopteris by determining the geographical distributions of their closest living relatives. We sequenced two chloroplast DNA fragments, rbcL and the trnL-F intergenic spacer (IGS), for 18 Hawaiian taxa, 45 non-Hawaiian taxa, and two outgroup species. For individual fragments, we estimated phylogenetic relationships using Bayesian inference and maximum parsimony. We performed a combined analysis of both cpDNA fragments employing Bayesian inference, maximum parsimony, and maximum likelihood. These analyses indicate that Hawaiian Dryopteris is not monophyletic, and that there were at least five separate colonizations of the Hawaiian Islands by different species of dryopteroid ferns, with most of the five groups having closest relatives in SE Asia. The results suggest that one colonizing ancestor, perhaps from SE Asia, gave rise to eight endemic taxa (the glabra group). Another colonizing ancestor, also possibly from SE Asia, gave rise to a group of five endemic taxa (the exindusiate group). Dryopteris fusco-atra and its two varieties, which are endemic to Hawai'i, most likely diversified from a SE Asian ancestor. The Hawaiian endemic Nothoperanema rubiginosum has its closest relatives in SE Asia, and while the remaining two species, D. wallichiana and D. subbipinnata, are sister species, their biogeographical origins could not be determined from these analyses due to the widespread distributions of D. wallichiana and its closest non-Hawaiian relative.     

Spore fitness components do not differ between diploid and allotetraploid species of Dryopteris (Dryopteridaceae)

BACKGROUND AND AIMS: Although allopolyploidy is a prevalent speciation mechanism in plants, its adaptive consequences are poorly understood. In addition, the effects of allopolyploidy per se (i.e. hybridization and chromosome doubling) can be confounded with those of subsequent evolutionary divergence between allopolyploids and related diploids. This report assesses whether fern species with the same ploidy level or the same altitudinal distribution have similar germination responses to temperature. The effects of polyploidy on spore abortion and spore size are also investigated, since both traits may have adaptive consequences. METHODS: Three allotetraploid (Dryopteris corleyi, D. filix-mas and D. guanchica) and three related diploid taxa (D. aemula, D. affinis ssp. affinis and D. oreades) were studied. Spores were collected from 24 populations in northern Spain. Four spore traits were determined: abortion percentage, size, germination time and germination percentage. Six incubation temperatures were tested: 8, 15, 20, 25 and 32 degrees C, and alternating 8/15 degrees C. KEY RESULTS: Allotetraploids had bigger spores than diploid progenitors, whereas spore abortion percentages were generally similar. Germination times decreased with increasing temperatures in a wide range of temperatures (8-25 degrees C), although final germination percentages were similar among species irrespective of their ploidy level. Only at low temperature (8 degrees C) did two allotetraploid species reach higher germination percentages than diploid parents. Allotetraploids showed faster germination rates, which would probably give them a competitive advantage over diploid parents. Germination behaviour was not correlated with altitudinal distribution of species. CONCLUSIONS: The results of this study suggest that (i) relative fitness of allopolyploids at sporogenesis does not differ from that of diploid parents and (ii) neither does allopolyploidization involve a change in the success of spore germination.     

Genetic variation in the allotetraploid Dryopteris corleyi (Dryopteridaceae) and its diploid parental species in the Iberian Peninsula

Studies on genetic diversity help us to unveil the evolutionary processes of species and populations and can explain several traits of diploid-polyploid complexes such as their distributions, their breeding systems, and the origin of polyploids. We examined the allozyme variation of Dryopteris aemula and D. oreades, diploid ferns with highly fragmented habitats, and the allotetraploid D. corleyi to (1) analyze the putative relationship between both diploids and the tetraploid, (2) compare the levels of genetic variation among species and determine their causes, and (3) assess the breeding system of these taxa. The allozymic pattern of D. corleyi confirms that it derived from D. aemula and D. oreades. The lack of genetic diversity in D. aemula, a species of lowland habitats, may be due to genetic drift associated with the contraction of populations in the last glaciation. By contrast, the alpine D. oreades had moderate intrapopulation genetic variation, which may derive from the expansion of populations during the last glaciation. In the latter species, low interpopulational variation suggested effective gene flow (spore exchange), and genotype frequencies in Hardy-Weinberg equilibrium indicated cross-fertilization of gametophytes. Evolutionary history appears to be an essential element in the interpretation of genetic variation of highly fragmented populations.     

A new Dryopteris (Pteropsida: Dryopteridaceae) species from south-central Africa

Dryopteris katangaensis , a new species endemic to the Katango–Zambian centre of endemism (Congo-Zambezi watershed) in Zambia and the Democratic Republic of Congo is described and illustrated. The morphological differences between the new species and D. schimperiana are discussed, and the ferns endemic to the Katango–Zambian Centre are reviewed.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 237–242.     

Anatomy of six species of Dryopteris ferns (Dryopteridaceae) from Mexico

Rhizome and foliar anatomy of the Mexican Dryopteris Adans. species were studied and compared with other Dryopteridaceae and other fern families to identify anatomical features with diagnostic value. The anatomy of rhizome, stipe, and blade is similar in species of the Dryopteris patula complex. The cells with un-lignified, thickened wall, with cap or U-shape around the meristeles belong to the collenchyma, in contrast with other fern families. Dryopteris wallichiana (Spreng.) Hyl. is anatomically distinguished from the other studied species by having more layers of sclerenchyma and meristeles on the stipe, and by the lack of sclereid nests on the rhizome. Dryopteris rossii C. Chr. and D. maxonii Underw. & C. Chr. are characterized by the presence of crystals on the periphery of rhizome nests. D. maxonni and D. wallichiana lack blade glands.     

湖南鳞毛蕨属(鳞毛蕨科)一新种

描述了鳞毛蕨属一新种,即吉首鳞毛蕨Dryopteris jishouensis G.X.Chen et D.G.Zhang.吉首鳞毛蕨与稀羽鳞毛蕨Dryopteris sparsa(Buch.-Ham.ex D.Don)O.Ktze.相似,区别在于本新种形体较小,通常高5³6cm,羽片近对生或互生,裂片边缘全缘且顶端钝圆而无尖齿,囊群盖边缘啮蚀状.     

Spore morphology of the genus Dryopteris Adans. (Dryopteridaceae) in Korea

Spore morphology of the Korean members of the genus Dryopteris was examined by scanning electron microscopy. In particular, spores of D. hangchowensis, D. woodsiisora, D. saxifragivaria, and D. subexaltata were examined here for the first time. Three perispore types were recognized on the basis of the shape of macro-ornamentations on perispore: these include rugate, echinate, and spinose. The rugate perispore type appeared to be the most common in the genus, and probably represents plesiomorphic condition in the genus Dryopteris. The echinate perispore type is found in D. expansa, and spinose perispore type in D. formosana. The results of this study demonstrate that the perispore characteristics, particularly the shape of macro-ornamentation and surface texture, have diagnostic value at the species level. Indeed, most of the Dryopteris taxa in Korea could be distinguished by their perispore characters. In addition, spores of sexual diploid individuals of D. saxifraga were much smaller than those of agamosporous triploid individuals, supporting the contention that the size of spores in ferns is generally related to ploidy levels.     

Phylogeny, divergence times, and historical biogeography of New World Dryopteris (Dryopteridaceae)

? Premise of the study: Dryopteris is a large, cosmopolitan fern genus ideal for addressing questions about diversification, biogeography, hybridization, and polyploidy, which have historically been understudied in ferns. We constructed a highly resolved, well-supported phylogeny for New World Dryopteris and used it to investigate biogeographic patterns and divergence times. ? Methods: We analyzed relationships among 97 species of Dryopteris, including taxa from all major biogeographic regions, with analyses based on 5699 aligned nucleotides from seven plastid loci. Phylogenetic analyses used maximum parsimony, maximum likelihood, and Bayesian inference. We conducted divergence time analyses using BEAST and biogeographic analyses using maximum parsimony, maximum likelihood, Bayesian, and S-DIVA approaches. We explored the monophyly of subgenera and sections in the most recent generic classification and of geographic groups of taxa using Templeton tests. ? Key results: The genus Dryopteris arose ca. 42 million years ago (Ma). Most of the Central and South American species form a well-supported clade which arose 32 Ma, but the remaining New World species are the result of multiple, independent dispersal and vicariance events involving Asia, Europe, and Africa over the last 15 Myr. We identified six long-distance dispersal events and three vicariance events in the immediate ancestry of New World species; reconstructions for another four lineages were ambiguous. ? Conclusions: New World Dryopteris are not monophyletic; vicariance has dominated the history of the North American species, while long-distance dispersal prevails in the Central and South American species, a pattern not previously seen in plants.     

Reticulate evolution on a global scale: a nuclear phylogeny for New World Dryopteris (Dryopteridaceae)

Reticulate, or non-bifurcating, evolution is now recognized as an important phenomenon shaping the histories of many organisms. It appears to be particularly common in plants, especially in ferns, which have relatively few barriers to intra- and interspecific hybridization. Reticulate evolutionary patterns have been recognized in many fern groups, though very few have been studied rigorously using modern molecular phylogenetic techniques in order to determine the causes of the reticulate patterns. In the current study, we examine patterns of branching and reticulate evolution in the genus Dryopteris, the woodferns. The North American members of this group have long been recognized as a classic example of reticulate evolution in plants, and we extend analysis of the genus to all 30 species in the New World, as well as numerous taxa from other regions. We employ sequence data from the plastid and nuclear genomes and use maximum parsimony (MP), maximum likelihood (ML), Bayesian inference (BI), and divergence time analyses to explore the relationships of New World Dryopteris to other regions and to reconstruct the timing and events which may have led to taxa displaying reticulate rather than strictly branching histories. We find evidence for reticulation among both the North and Central/South American groups of species, and our data support a classic hypothesis for reticulate evolution via allopolyploid speciation in the North America taxa, including an extinct diploid progenitor in this group. In the Central and South American species, we find evidence of extensive reticulation involving unknown ancestors from Asia, and we reject deep coalescent processes such as incomplete lineage sorting in favor of more recent intercontinental hybridization and chloroplast capture as an explanation for the origin of the Latin American reticulate taxa.     

Phylogenetics of Chinese Dryopteris (Dryopteridaceae) based on the chloroplast rps4-trnS sequence data

Dryopteris is one of the largest and most taxonomically complex fern genera in the Dryopteridaceae, with 127 species occurring throughout temperate, sub-temperate, subtropical, and tropical China. Investigations of the evolutionary relationships of a subset of these Chinese Dryopteris species, using DNA sequence-based methods, specifically tested the monophyly of the genus and the validity of the previous subgeneric classifications. Sixty species of Dryopteris, four closely related non-Dryopteris and three species of Arachniodes, were used as outgroup taxa. The rps4-trnS region of the chloroplast genome was sequenced in these species for the first time. Both maximum parsimony (MP) and neighbor-joining (NJ) analyses identified six polyphyletic clades that contained Dryopteris species. These results were supported by a Bayesian analysis of the same data set. The phylogenetic patterns strongly suggest the polyphyletic status of Dryopteris; the monophyletic groupings of the species do not correspond with either Fraser-Jenkins [In: Bull Brit Mus (Nat Hist) Bot 14(3):183–218, 1986} or Wu (In: Flora Reipublica Popularis Sinicae Tomus 5 (1) pp 1–241, 2000] subgeneric classification of Dryopteris, except in a few specific cases. This work represents the first molecular systematic analyses of Chinese Dryopteris, and we propose the next steps necessary to recognize new subgenera of the genus.     

Morphological and chromosomal variation of the Dryopteris varia (L.) Kuntze complex (Dryopteridaceae) in Korea

The Dryopteris varia complex is highly variable in morphology, resulting in taxonomic confusion in delimiting taxon boundaries and determining relationships. We have examined the variation in morphology, chromosome number and mode of reproduction of the Korean members of the D. varia complex to clarify their taxonomic identities. Landmark analysis of the leaf blades and pinnae and the principal components analysis of 31 morphological characters revealed seven entities within the D. varia complex in Korea; these comprise D. varia s. str., D. pacifica, D. sacrosancta, D. bissetiana, D. saxifraga, D. saxifragivaria, and the Suak population which is considered to be a new taxon. Mitotic chromosome counts and examination of reproduction modes indicated that D. bissetiana in Korea appears to be agamosporous with diploid (2n = 82) or triploid (2n = 123) chromosome numbers. However, D. saxifraga is sexual diploid or agamosporous triploid, and the other taxa are agamosporous triploid. Dryopteris bissetiana, D. saxifraga and D. saxifragivaria are similar in major morphological characteristics, but show differences in attachment and shape of rachis scales. The results also suggest that agamosporous triploid D. saxifragivaria was probably derived from hybridization between sexual diploid D. saxifraga and D. bissetiana.     

中国云南鳞毛蕨属(鳞毛蕨科)13种植物的染色体数目

报道了中国云南产鳞毛蕨科Dryopteridaceae鳞毛蕨属Dryopteris Adanson 13种植物的染色体数目。其中4个种：多雄拉鳞毛蕨D．alpestris（2n=82）、哈巴鳞毛蕨D．habaensis（2n=82）、脉纹鳞毛蕨D．lachoongensis（2n=82）和永自鳞毛蕨D．yungtzeensis（2n=82）的染色体数目为首次报道;无融合三倍体的川西鳞毛蕨Dryopteris rosthornii、无融合四倍体的大羽鳞毛蕨D．wallichiana以及无融合二倍体的栗柄鳞毛蕨D．yoroii为3个新发现的细胞类型。细胞学研究结果支持高山鳞毛蕨组sect．CaespitosaeS．G Lu应该为鳞毛蕨属内一个独立的组;中国喜马拉雅地区的鳞毛蕨属植物中存在着大量的无融合二倍体细胞类型。对蕨类植物中同一植株产生不同倍性孢子的现象进行了讨论。     

Origin of Dryopteris shibipedis (Dryopteridaceae), a fern species extinct in the wild

Dryopteris shibipedis was once treated as an extinct species in the Red List (2007) by the Japanese Ministry of the Environment, but 'rediscovered' in the Tsukuba Botanical Garden. To clarify its origin, using 'overlooked' cultivated stocks we analyzed nuclear PgiC intron sequences. As the PgiC genotype of D. shibipedis can be explained by a combination of alleles of D. kinkiensis and those of D. pacifica, the hypothesis of hybrid origin of the species is supported.     

New species in the fern genus Dryopteris (Dryopteridaceae) from the islands in the Gulf of Guinea (West Africa)

Three new species of Dryopteris, D. cicatricata J.P. Roux and D. caperata J.P. Roux from São Tomé and D. aurantiaca J.P. Roux from Annobón are described. All three taxa appear to be local endemics. A key to the Dryopteris species occurring on the islands in the Gulf of Guinea is provided.     

Electrophoretic evidence for homoeologous chromosome pairing in the apogamous fern species<Emphasis Type="Italic"> Dryopteris nipponensis</Emphasis> (Dryopteridaceae)

Segregation of genotypes through homoeologous chromosome pairing in the apogamous species Dryopteris nipponensis was tested by electrophoretic analysis. Of 284 progeny examined (250 gametophytes and 34 sporophytes), from the parental sporophyte with the Pgi-2 genotype abc, five showed different genotypes from that of the parent (three aac, one bbc and one bcc). This is the first evidence for genetic segregation in the progeny of apogamous fern species. Electronic Publication     

Morphogenesis of the sexual phase of six Mexican species of the Dryopteris (Dryopteridaceae), Part II]

The development of the sexual phase of six Mexican species of Dryopteris is described and compared. Spores of all studied species are monolete, ellipsoid and have a rugose surface; the perine is folded, brown to dark brown, with a tubercled outline. Germination pattern is of the Vittaria-type and the development pattern of the prothallia is of the Aspidium-type. Gametangia are of the common type for the leptosporangiate advanced ferns. First leaves of the sporophytes appear 258-265 after sowing and apparently in Dryopteris pseudo-filix-mas the sporophyte have an apogamic origin (80 days). To make a comparative analysis of gametophytic characteristics in the twelve Mexican species and conclude of germination is of the Vittaria-type and development pattern prothallial is of the Aspidium-type, and unicelular trichomes on margin and superficial gametophytic to yield irregular aspect are characteristics to yield unit and characteristic to genera to conform Dryopteridaceae family (sensu Moran 1995) with the exception of Didymochlaena genus.     

A revision of Dryopteris sect. Diclisodon (Dryopteridaceae) based on morphological and molecular evidence with description of a new species

Dryopteris sect. Diclisodon is a small section of ferns with about 12 species mainly distributed in East Asia. Here, we carried out morphological and phylogenetic analyses of this section. A new species from southwest China, D. gaoligongensis, is described and illustrated. Dryopteris gaoligongensis resembles D. indonesiana and D. sparsa, but differs by having a creeping rhizome and large 4-pinnate fronds. We also show that D. glabrior Ching & Z.Y. Liu is a distinct species; however, because it is a later homonym of D. glabrior Copel., it should be renamed D. renchangiana. We conclude that a species previously known as D. nitidula, also an illegitimate homonym, should be recognized with a new name, D. sinonepalensis. We resolve the phylogenetic position of D. yoroii as sister to other sampled species of D. sect. Diclisodon. Our phylogenetic analyses confirm the distinctiveness of D. gaoligongensis, D. renchangiana, and D. sinonepalensis. A key to species of D. sect. Diclisodon in China is provided.