Interaction dynamics between saprobic lignicolous fungi and Armillaria in controlled environments: Exploring the potential for competitive exclusion of Armillaria on peach

Armillaria root rot, caused by Armillaria tabescens and Armillaria mellea, is a major cause of premature tree death in peach orchards in the southeastern United States. The root systems of infected trees can become entirely colonized by Armillaria, serving as an inoculum source for adjacent trees and providing massive inoculum levels in replant situations. If dead or dying trees could be colonized by an effective competitor of Armillaria before their removal, the extent of root colonization by the pathogen could be reduced, thus decreasing the threat to adjacent trees and/or subsequent plantings. Interactions between five species of saprobic lignicolous fungi (Ganoderma lucidum, Hypholoma fasciculare, Phanerochaete velutina, Schizophyllum commune, and Xylaria hypoxylon) and the two Armillaria species were examined in controlled conditions to provide proof of concept for competitive exclusion of Armillaria from peach roots. On agar-coated glass slides, all five potential antagonists induced detrimental reactions in >58% of the Armillaria hyphae observed, with the majority resulting in hyphal swelling or granulation. On poplar wood blocks, all antagonists consistently either overgrew Armillaria colonies or—in the case of S. commune—engaged in deadlock reactions; in all cases, the viability of Armillaria colonies was reduced to <30% of that of unchallenged controls. When inoculated simultaneously onto opposite ends of peach root segments, all antagonists consistently reduced growth and viability of Armillaria on and under the bark, whereby reduction of pathogen growth underneath the bark, Armillaria’s primary ecological niche, was most pronounced for G. lucidum, S. commune, and X. hypoxylon. When root segments were allowed to be colonized entirely by Armillaria before being inoculated with the antagonists, the latter were able to overgrow the pathogen on the root surface but unable to pre-empt it from underneath the bark. In summary,G. lucidum, S. commune, and X. hypoxylon caused strong hyphal and mycelial interference reactions and the most pronounced reductions in growth of Armillaria above and below the bark, indicating that they would be the most promising candidates for field-scale evaluations to restrict colonization of dead or dying peach trees by Armillaria in the orchard.     

Species identity of geographically distinct populations of the glassy-winged sharpshooter parasitoid Gonatocerus ashmeadi: morphology, DNA sequences, and reproductive compatibility

Gonatocerus ashmeadi is a common and seemingly widespread egg parasitoid of Homalodisca coagulata, the glassy-winged sharpshooter (GWSS). Location records for G. ashmeadi indicate its natural range to be the southeastern USA and northeastern Mexico (which coincides with the presumed native range of GWSS), and possibly southern and central California (CA) (the adventive range of GWSS). The purpose of our work was to determine whether G. ashmeadi in the USA and northeastern Mexico is one species or a complex of reproductively incompatible sibling species. We used three approaches to determine the species identity of different G. ashmeadi populations: (1) reassessment of key morphological features using scanning electron microscopy (SEM) to determine if subtle morphological differences exist between G. ashmeadi populations which could indicate species differences; (2) to determine if molecular differences exist between G. ashmeadi populations collected from different regions by comparing mitochondrial and ribosomal DNA sequences; (3) mating compatibility studies to determine if different populations of G. ashmeadi are reproductively isolated, or if mating occurs, whether offspring are viable thereby defining species groups on the basis of successful interbreeding. Results from these three areas (morphology, DNA sequences, and reproductive compatibility) have been evaluated collectively; leading us to the conclusion that G. ashmeadi as it is currently viewed is a valid species and not an aggregate of morphologically indistinguishable cryptic species.     

Molecular characterization of strawberry pathogen Gnomonia fragariae and its genetic relatedness to other Gnomonia species and members of Diaporthales

Gnomonia fragariae is a poorly studied ascomycete belonging to Diaporthales. Originally G. fragariae was considered a saprophyte occurring on dead tissues of strawberry plants. Recently this fungus was found in Latvia and Sweden, and it was proven to be the cause of severe root rot and petiole blight of strawberry. Thirteen isolates of this pathogen and several other Gnomonia species occurring on rosaceous hosts were characterized by molecular analysis using nucleotide sequences of partial LSU rRNA gene and the total ITS region. The homologous regions from relevant diaporthalean taxa available in the GenBank were also included and compared with the taxa sequenced in this study. Phylogenetic analyses revealed that G. fragariae, G. rubi, and Gnomonia sp. (CBS 850.79) were genetically different from G. gnomon, the type species of the genus, and other members of Gnomoniaceae. The analyses showed that G. fragariae and Hapalocystis were genetically very closely related, forming a phylogenetic clade, which is possibly presenting a new family in the Diaporthales. Morphological comparisons of the Gnomonia species on the basis of commonly used criteria for the taxonomy of Diaporthales, so far did not reveal any evident features for the polyphyletic status of Gnomonia.     

不同平茬年限人工柠条林光合特性及土壤水分的响应变化

平茬是荒漠草原老化人工柠条林营林抚育的重要措施,为系统认识柠条平茬后连续的生理与生态响应过程及其变化规律,该研究设置对比观测样地,以未平茬柠条(WPC)为对照,以平茬后连续生长1～5年(PC1～PC5)的柠条为处理,对各样地柠条净光合速率、蒸腾速率、气孔导度、胞间CO2浓度、水分利用效率等光合生理特征及其土壤含水量分布的影响进行测定分析。结果表明:(1)平茬处理对柠条生理特性的影响因平茬年限的增加而异,其中PC1和PC2柠条的净光合速率和蒸腾速率较WPC略有提高,PC1柠条处于补偿生长的活跃期,水分利用效率明显高于其他平茬处理,PC2柠条的水分利用效率开始下降;PC3和PC4的柠条蒸腾速率、净光合速率和气孔导度显著上升,且PC4处理下达到最大值,相应水分利用效率也逐步回升;PC5的柠条几乎不存在补偿性生长,净光合速率、蒸腾速率和水分利用效率开始回落,逐渐接近WPC;平茬措施对PC1与PC5柠条胞间CO2浓度大小的影响较大。(2)PC1的土壤水分含量在0～100cm土层因受冠层截留大幅减小的影响而低于其他年限平茬处理;PC2的土壤水分略有改善,PC3、PC4的土壤含水量显著提高,PC5的土壤水分状况则逐渐接近于WPC。(3)随平茬年限的增加,柠条光合特性与土壤含水量间存在一定的动态互馈关系,其中PC1的土壤水分略有下降,柠条生长减缓;PC2土壤含水量逐步恢复;PC3土壤含水量增长幅度开始下降,柠条的各项生理指标上升;PC4柠条的光合生理指标、土壤含水量都达到了最高值;PC5柠条的各项指标开始下降。研究发现,PC4处理是柠条光合生理和土壤水分响应变化的拐点,可参考作为平茬柠条优化管理的一个时间节点。     

Susceptibility of Helicoverpa zea and Heliothis virescens (Lepidoptera: Noctuidae) to Vip3A insecticidal protein expressed in VipCot™ cotton

Susceptibility of laboratory and field colonies of Helicoverpa zea (Boddie) and Heliothis virescens F. to Vip3A insecticidal protein was studied in diet incorporation and diet overlay assays from 2004 to 2008. Responses of field populations were compared to paired responses of University of Arkansas laboratory susceptible H. zea (LabZA) and H. virescens (LabVR) colonies. After 7 d of exposure, observations were made on number of dead larvae (M) and the number of larvae alive but remaining as first instars (L1). Regression estimates using M (LC₅₀) and M plus L1 (MIC₅₀) data were developed for laboratory and field populations. Susceptibility of laboratory and field populations exposed to Vip3A varied among different batches of protein used over the study period. Within the same batch of Vip3A protein, susceptibilities of laboratory colonies of both species (LabZA and LabVR) were similar. Field colonies were significantly more susceptible to Vip3A than the respective reference colonies of both species. Within field populations, susceptibility to Vip3A varied up to 75-fold in H. zea and 132-fold in H. virescens in LC₅₀ estimates. Variabilities in MIC₅₀s were up to 59- and 11-fold for H. zea and H. virescens, respectively.     

中间锦鸡儿WRKY75基因对拟南芥耐受盐和ABA能力的影响

该研究从旱生灌木中间锦鸡儿中克隆得到1个CiWRKY75基因。序列分析显示,CiWRKY75开放阅读框长570bp,编码189个氨基酸,含有1个WRKYGQK基序和1个C2H2型锌指结构,属于第二类WRKY转录因子。亚细胞定位显示,CiWRKY75定位于细胞核。实时荧光定量PCR检测表明,CiWRKY75基因的表达受盐胁迫和ABA诱导。在拟南芥中过量表达CiWRKY75后,与野生型拟南芥相比,转基因株系种子的萌发率在盐胁迫下降低,并且对盐胁迫的耐受能力明显减弱;ABA处理下,2个转基因株系的种子萌发率(10.3%、9.6%)较野生型(25.9%)明显降低。研究表明,CiWRKY75是中间锦鸡儿对盐和ABA响应的重要调控因子。     

Characterisation of cell wall polysaccharides, arabinogalactans-proteins (AGPs) and phenolics of Cola nitida, Cola acuminata and Garcinia kola seeds

Many Cola plant species are endemic to West and Central Africa. Cola acuminata and Cola nitida are used as masticatory when fresh, while the dried nuts are used for beverages and pharmaceutical purposes in Europe and North America. Garcinia kola seeds, that serve as a substitute for the true kola nuts, are used in African traditional medicine for the treatment of various diseases, including colic, headache and liver cirrhosis. Seeds extracts of G. kola are also known for their anti-inflammatory, antimicrobial and antiviral properties. To gain information on the chemical properties of the kolas, we have isolated and analyzed cell wall polysaccharides, arabinogalactan-proteins and phenolic substances from the seeds of the three kola species. The sugar composition of cell wall material of C. acuminata, C. nitida and G. kola revealed that Gal (up to 30%), Ara, GalA and Glc as the predominant monosaccharides, representing approximately 90% by mol of the total hydrolysable sugar present in this material. In Ammonium oxalate cell wall fraction, GalA was found to be the major sugar present in all kola species. In the alkali-soluble fraction, there were significant differences in the level of Glc and Gal. The level of Glc was high in C. acuminata and C. nitida while the level of Gal and Xyl were high in C. nitida and G. cola. Isolation and quantification of arabinogalactan-proteins demonstrate that G. kola seeds contained four to eight times more of these proteoglycans than the seeds of the other two species. Finally, analysis of soluble phenolic substances shows that caffeine and catechin were largely represented in C. acumina and C. nitida seeds, with caffeine accounting for 50% of all soluble phenolics. These findings indicate that the three Kola seeds are highly enriched in pectins and proteoglycans and that C. acuminata and C. nitida can be used as a possible source of caffeine and catechin.     

平茬密度对荒漠草原人工柠条林间生境的影响

合理平茬对柠条林更新复壮及科学利用具有重要意义。以宁夏荒漠草原6 m带距人工柠条林（中间锦鸡儿,Caragana intermedia）林间草原为研究对象,研究了全平（QP）、隔一带平茬两带（G1P2）、隔一带平茬一带（G1P1）、隔两带平茬一带（G2P1）、未平茬（WP）五种密度（间距）平茬后柠条林间植被和土壤性状、小气候和土壤风蚀特征等变化。结果表明：（1）G2P1处理下林间植被物种总数、密度、高度和地上生物量最高,物种丰富度、多样性指数以G1P1、G2P1较高。（2）0-40 cm土壤容重以G1P1、G2P1较低,但机械组成无明显变化规律;土壤有机质、速效钾、全氮和速效氮以G2P1最高,但速效磷G1P1最高;土壤平均含水量以G2P1较高,达到8.33%,G1P2和WP最低,WP水分垂直变异系数最大。（3）处理间气温和风速无显著差异;风蚀量以QP、G1P2和WP较高,G1P1与G2P1较小。研究认为,适宜的密度平茬对人工柠条林间生境有改善作用,宁夏荒漠草原人工柠条林平茬时可采取隔两带平茬一带的方式。     

Interaction between uranium and the cytochrome c 3 of Desulfovibrio desulfuricans strain G20

Cytochrome c₃ of Desulfovibrio desulfuricans strain G20 is an electron carrier for uranium (VI) reduction. When D. desulfuricans G20 was grown in medium containing a non-lethal concentration of uranyl acetate (1 mM), the rate at which the cells reduced U(VI) was decreased compared to cells grown in the absence of uranium. Western analysis did not detect cytochrome c₃ in periplasmic extracts from cells grown in the presence of uranium. The expression of this predominant tetraheme cytochrome was not detectably altered by uranium during growth of the cells as monitored through a translational fusion of the gene encoding cytochrome c₃ (cycA) to lacZ. Instead, cytochrome c₃ protein was found tightly associated with insoluble U(IV), uraninite, after the periplasmic contents of cells were harvested by a pH shift. The association of cytochrome c₃ with U(IV) was interpreted to be non-specific, since pure cytochrome c₃ adsorbed to other insoluble metal oxides, including cupric oxide (CuO), ferric oxide (Fe₂O₃), and commercially available U(IV) oxide.An erratum to this article can be found at     

The potential of Ulocladium botrytis for biological control of Orobanche spp.

A strain of Ulocladium botrytis isolated from diseased Orobanche crenata shoots caused disease on the parasitic weed in pathogenicity tests. The potential of the fungus to be developed as a mycoherbicide for Orobanche spp. was further investigated. Although the fungus significantly decreased O. crenata germination in vitro by 80%, it did not generally lead to a decreased number of O. crenata shoots or tubercles in inoculated root chambers or pots. However, the number of diseased or dead tubercles and underground shoots was significantly increased compared to the noninoculated treatments. Postemergence inoculation of O. crenata shoots with a conidial suspension resulted in the death of almost all inoculated plants 14 days after application under greenhouse conditions. In preliminary host-range studies, the pathogen caused disease on Orobanche cumana on sunflower whereas on Orobanche aegyptiaca shoots parasitizing tomato only minimal disease symptoms could be detected after postemergence inoculation. Based on the results of our investigations, we conclude that Ulocladium botrytis has only a limited potential to be used as a biocontrol agent against Orobanche spp.     

The introduction and release of Chiasmia inconspicua and C. assimilis (Lepidoptera: Geometridae) for the biological control of Acacia nilotica in Australia

Two geometrid moths Chiasmia inconspicua and Chiasmia assimilis, identified as potential biological control agents for prickly acacia Acacia nilotica subsp. indica, were collected in Kenya and imported into quarantine facilities in Australia where laboratory cultures were established. Aspects of the biologies of both insects were studied and CLIMEX® models indicating the climatically favourable areas of Australia were developed. Host range tests were conducted using an approved test list of 74 plant species and no-choice tests of neonate larvae placed on both cut foliage and potted plants. C. inconspicua developed through to adult on prickly acacia and, in small numbers, Acacia pulchella. C. assimilis developed through to adult on prickly acacia and also in very small numbers on A. pulchella, A. deanei, A. decurrens, and A. mearnsii. In all experiments, the response on prickly acacia could be clearly differentiated from the responses on the non-target species. Both insects were approved for release in Australia. Over a three-year period releases were made at multiple sites in north Queensland, almost all in inland areas. There was no evidence of either insect’s establishment and both colonies were terminated. A new colony of C. assimilis was subsequently established from insects collected in South Africa and releases of C. assimilis from this new colony were made into coastal and inland infestations of prickly acacia. Establishment was rapid at one coastal site and the insect quickly spread to other infestations. Establishment at one inland area was also confirmed in early 2006. The establishment in coastal areas supported a CLIMEX model that indicated that the climate of coastal areas was more suitable than inland areas.     

复轮生暗孢小克银汉霉新变种及其与原变种之间的配合

多年前分离自湖北神农架林中采回的一份土样的一株小克银汉霉Cu137最近经我们研究定名为复轮生暗孢小克银汉霉新变种(Cunninghamella phaeospora Boedijn var.multiverticillata var. nov.)。它与暗孢小克银汉霉原变种(Cunninghamella phaeospora Boedijnvar. phaeospora)的异同在于:(1)两者均具有单轴分枝、分枝单生或成对的孢子枝,不同的是新变种的孢子枝除单轴分枝外还可轮状分枝,或单轴与轮状混合分枝,轮状分枝可多达3轮,每轮由3-8分枝组成,原变种则完全不形成轮状分枝;(2)两者的孢子枝主轴上的顶生泡囊均具各种形状并略呈棱角状,但新变种的侧枝上的饱囊常常是棒形的,原变种的侧枝上的饱囊则很少棒形;(3)新变种的假根很发达,可自菌丝、匍匐菌丝、孢子枝、泡囊等部位发生,而原变种的假根一般不很发达,而且只从菌丝或甸旬菌丝发生;(4)两者的小型孢子囊在形状、大小、刺等方面一致,但新变种的小型孢子囊无色至淡褐色,原变种的小型孢子囊则为淡褐色至深褐色;(5)新变种的菌落白色,至多在老后污白色至极浅的淡褐色,原变种的菌落自始即为深灰色。除暗孢小克银汉霉原变种外,同属中还有另外三个分类群与复轮生暗孢小克银汉霉较为接近:印度小克银汉霉(Cunninghamella indica Baijal & B. S. Mehrotra)与印度刺孢小克银汉霉[Cunninghamella echinulata(Thaxt.) Thaxt. ex Blakeslee var. indica Baijal & B. S. Mehrotra]因菌落白色及孢子枝分枝棒形,轮生小克银汉霉(Cunninghamella verticillaata Paine)因孢子枝具数轮轮生分枝而与复轮生暗孢小克银汉霉这个新变种有一定的相似。但是,新变种无论是顶生泡囊还是侧生泡囊的直径都较上述三个分类群小得多;新变种的顶生饱囊往往不规则形状且略带棱角,而上述三个分类群则不是这样。还有,新变种的孢子枝分枝方式与印度小克银汉霉的颇为不同,新变种的小型孢子囊比印度刺孢小克银汉霉的小得多,其小型孢子囊主要球形至近球形,与轮生小克银汉霉的椭圆形至卵形也不一样。此外,新变种的假根系统极其发达,与同属中任何一种均不相同。将复轮生暗孢小克银汉霉新变种Cu137(+)与暗孢小克银汉霉原变种的一株分离自香港山边土壤的Cu 136(一)配合时只形成配子囊,但与原变种的模式菌株CBS 692.68(-)配合时则可形成少量的接合孢子囊。为了获得更多的接合孢子囊以观察它们是否可育的,我们将Cu 137和CBS 692.68同时接种到许多培养皿上,然后制片观察。用姆指轻轻、重复压盖玻片,可使接合孢子囊破裂以观察其内含物。结果,从100个以上的接合孢子囊中,仅在其中4个发现有接合孢子的形成,其余的都是空的和不育的。由于原变种尚未发现(+)配合型菌株,新变种则未发现(-)配合型菌株,原变种与原变种之间及新变种与新变种之间配合形成的有性型尚未获得,而且全世界均未见有报道,无法和新变种与原变种之间配合形成的有性型相比较,因此目前尚不能肯定新变种与原变种之间形成的有性型在形态上是否能代表这个种的有性型。但是,尽管如此,暗孢小克银汉霉的这两个变种之间配合形成的有性型的形态仍然是很有特征性的,足以把它与其它种的已知有性型相区别。     

Biology, host range, and risk assessment supporting release in Africa of Falconia intermedia (Heteroptera: Miridae), a new biocontrol agent for Lantana camara

The ornamental hybrid shrub, Lantana camara L. (lantana), is a serious environmental weed and has been targeted for biological control in South Africa since 1961. The established biocontrol agents cause insufficient levels of damage and additional natural enemies are required to reduce the invasiveness of this weed. The lantana mirid, Falconia intermedia (Distant), is a promising new agent that was imported from the Caribbean for life history and host-range studies. The nymphs and adults are leaf-suckers that cause chlorotic speckling, which reduces the photosynthetic capacity of the plant. Biological studies indicate that F. intermedia has considerable biocontrol potential, in that it has a high intrinsic rate of increase, the potential for multiple generations a year, highly mobile adults, and a high level of damage per individual. Host-specificity trials indicated that the lantana mirid has a narrow host range, with L. camara being the most suitable host, but several indigenous African species in the closely related genus Lippia are suitable alternative host plants. Under multiple-choice conditions, adults showed a significant and strong oviposition preference for L. camara over the Lippia species. A risk assessment of potential nontarget effects indicated that three Lippia species could sustain damage levels in the field. The relatively low probability of damage to indigenous species was considered a justified trade-off for the potentially marked impact on L. camara. The regulatory authorities accepted the results of this study and F. intermedia was released against L. camara in South Africa in April 1999.     

中间锦鸡儿CiMYB68基因克隆及表达分析

该研究以中间锦鸡儿(Caragana intermedia)为材料,利用RACE技术克隆了CiMYB68基因的全长序列。对CiMYB68的基因组DNA和cDNA全长分析显示,CiMYB68基因无内含子,开放阅读框为852bp,编码284个氨基酸。预测CiMYB68基因编码的蛋白质等电点为8.95,分子量约为31 459.4Da。序列比对和系统进化分析表明,该蛋白和大豆的GmMYB68一致性最高,达到67%。构建了CiMYB68基因与GFP融合表达质粒,激光共聚焦显微镜观察发现,融合蛋白定位于细胞核。用实时荧光定量PCR技术对在不同胁迫条件下CiMYB68基因的表达检测结果表明,在干旱和低温处理下CiMYB68均受到不同程度的诱导,暗示CiMYB68基因可能与中间锦鸡儿响应逆境胁迫有关。     

Genetic characterizations of Cryptosporidium spp. and Giardia duodenalis in humans in Henan, China

Cryptosporidium and Giardia infections are common causes of diarrhea worldwide. To better understand the transmission of human cryptosporidiosis and giardiasis in Henan, China, 10 Cryptosporidium-positive specimens and 18 Giardia-positive specimens were characterized at the species/genotype and subtype levels. Cryptosporidium specimens were analyzed by DNA sequencing of the small subunit rRNA and 60 kDa glycoprotein genes. Among those genotyped, nine belonged to C. hominis and one C. felis, with the former belonging to three subtype families: Ia, Ib, and Id. The three Ib subtypes identified, IbA16G2, IbA19G2, and IbA20G2, were very different from the two common Ib subtypes (IbA9G3 and IbA10G2) found in other areas of the world. The distribution of Giardia duodenalis genotypes and subtypes was assessed by sequence analysis of the triosephosphate isomerase (tpi) gene. The assemblages A (eight belonging to A-I and four A-II) and B (belonging to six new subtypes) were found in 12 and six specimens, respectively. More systematic studies are needed to understand the transmission of Cryptosporidium and G. duodenalis in humans in China.     

A comparative study on the antimutagenic properties of aqueous extracts of Aspalathus linearis (rooibos), different Cyclopia spp. (honeybush) and Camellia sinensis teas

Antimutagenic activity of aqueous extracts of the South African herbal teas, Aspalathus linearis (rooibos) and Cyclopia spp. (honeybush) was compared with that of Camellia sinensis (black, oolong and green) teas in the Salmonella mutagenicity assay using aflatoxin B₁ (AFB₁) and 2-acetylaminofluorene (2-AAF) as mutagens. The present study presents the first investigation on antimutagenic properties of C. subternata, C. genistoides and C. sessiliflora. The herbal teas demonstrated protection against both mutagens in the presence of metabolic activation, with the exception of “unfermented” (green/unoxidised) C. genistoides against 2-AAF, which either protected or enhanced mutagenesis depending on the concentration. Antimutagenic activity of “fermented” (oxidised) rooibos was significantly (P < 0.05) less than that of Camellia sinensis teas against AFB₁, while for 2-AAF it was less (P < 0.05) than that of black tea and similar (P > 0.05) to that of oolong and green teas. Antimutagenic activity of unfermented C. intermedia and C. subternata exhibited a similar protection as fermented rooibos against AFB₁. Against 2-AAF, fermented rooibos exhibited similar protective properties than unfermented C. intermedia and C. sessiliflora. Unfermented rooibos was less effective than the C. sinensis teas and fermented rooibos, but had similar (P > 0.05) antimutagenicity to that of fermented C. sessiliflora against AFB₁ and fermented C. subternata against 2-AAF. Fermented C. intermedia and C. genistoides exhibited the lowest protective effect against 2-AAF, while fermented C. intermedia exhibited the lowest protection when utilising AFB₁ as mutagen. Aspalathin and mangiferin, major polyphenols in rooibos and Cyclopia spp., respectively, exhibited weak to moderate protective effects when compared to the major green tea catechin, (−)epigallocatechin gallate (EGCG). Antimutagenic activity of selected herbal tea phenolic compounds indicated that they contribute towards (i) observed antimutagenic activity of the aqueous extracts against both mutagens and (ii) enhancement of the mutagenicity of 2-AAF by unfermented C. genistoides. Antimutagenic activity of the South African herbal teas was mutagen-specific, affected by fermentation and plant material, presumably due to changes and variation in phenolic composition.     

Phylogeny and biogeography of Chinese and Australasian Polystichum ferns as inferred from chloroplast trnL-F and rps4-trnS sequence data

Polystichum, one of the largest genera of ferns, occurs worldwide with the greatest diversity in southwest China and adjacent regions. Although there have been studies of Chinese Polystichum on its traditional classification, geographic distributions, and even a few on its molecular systematics, its relationships to other species outside China remain little known. Here, we investigated the phylogeny and biogeography of the Polystichum species from China and Australasia. The evolutionary relationships among 42 Polystichum species found in China (29 taxa) and Australasia (13 taxa) were inferred from phylogenetic analyses of two chloroplast DNA sequence data sets: rps4-trnS and trnL-F intergenic spacers. The divergence time between Chinese and Australasian Polystichum was estimated. The results indicated that the Australasian species comprise a monophyletic group that is nested within the Chinese diversity, and that the New Zealand species are likewise a monophyletic group nested within the Australasian species. The divergence time estimates suggested that Chinese Polystichum migrated into Australasia from around 40 Ma ago, and from there to New Zealand from about 14 Ma. The diversification of the New Zealand Polystichum species began about 10 Ma. These results indicated that Polystichum probably originated in eastern Asia and migrated into Australasia: first into Australia and then into New Zealand.