Fine-level mycorrhizal specificity in the Monotropoideae (Ericaceae): specificity for fungal species groups

The Monotropoideae (Ericaceae) are non-photosynthetic angiosperms that obtain fixed carbon from basidiomycete ectomycorrhizal fungi. In previous work, we showed that each plant species is associated with a single genus or a set of closely related genera of ectomycorrhizal fungi. Here we show that the level of specificity is much higher. We used a molecular phylogenetic approach to contrast specificity patterns among eight plant lineages and three fungal genera. We relied on fungal nuclear internal transcribed spacer (nrITS) sequence data obtained from 161 basidiocarps and 85 monotropoid roots representing 286 sampled plants screened using restriction length polymorphisms. From the phylogenetic placement of fungal symbionts in fungal phylograms, we found that three basal (Sarcodes, Pterospora, Pleuricospora) and one derived lineage (Allotropa) of plants target narrow clades of closely related species groups of fungi, and four derived lineages (Monotropa hypopithys species group, Pityopus) target more distant species groups. Within most plant lineages, geography and photobiont association constrain specificity. Specificity extended further in Pterospora andromedea, in which sequence haplotypes at the plastid trn L-F region of 73 plants were significantly associated with different fungal species groups even in sympatry. These results indicate that both the macro- and microevolution of the Monotropoideae are tightly coupled to their mycorrhizal symbionts.     

Comparative analysis of the reproductive ecology of Monotropa and Monotropsis: Two mycoheterotrophic genera in the Monotropoideae (Ericaceae)

Studies of mycoheterotrophs, defined as plants that obtain carbon resources from associated mycorrhizal fungi, have fundamentally contributed to our understanding of the importance and complexity of symbiotic ecological interactions. However, to date, the reproductive ecology of these organisms remains empirically understudied, with existing literature presenting hypotheses about traits including a generalist pollination syndrome and autogamous self-pollination. To address this gap in our knowledge of the reproductive ecology of mycoheterotrophic plants, we comparatively analyzed three species of two monotropoid genera, Monotropa and Monotropsis. During three consecutive years of field observations and manipulations of four populations of Monotropa uniflora, seven of M. hypopitys (both red and yellow color forms), and two of Monotropsis odorata, we investigated flowering phenology, pollination ecology, breeding system, floral herbivory, and reproductive effort and output. Contrary to previous predictions, our results revealed that taxa are largely outcross-pollinated and specialized toward Bombus pollinators. Additionally, species differ in breeding system, timing and duration of reproductive development, fluctuations in reproductive effort and output, and fitness impacts of herbivory. This study is the first thorough investigation of the reproductive ecology of mycoheterotrophic species and provides insight into possible limitations in reproductive traits imposed by a mycoheterotrophic life history.     

Unusual patterns of hybridization involving a narrow endemic Rhododendron species (Ericaceae) in Yunnan, China

? Premise of the study: One potential threat to rare species is genetic swamping caused by hybridization, but few studies have quantified this threat. Rhododendron cyanocarpum is a narrow endemic species that occurs sympatrically with potentially interfertile congeners throughout its range within Yunnan, China. We searched the entire distribution of R. cyanocarpum for hybrids and examined the patterns of hybridization to assess potential threat from hybridization. ? Methods: In a comprehensive field survey, we detected only one instance of hybridization involving R. cyanocarpum, with R. delavayi, at Huadianba near Dali. Material of both species and putative hybrids was examined using morphology, chloroplast DNA, nuclear ribosomal DNA, and Bayesian analysis of AFLP profiles. ? Key results: Of 10 putative hybrids, two were F(1)(')s and at least seven were F(2)(')s. Four backcrosses to R. delavayi were detected among material with R. delavayi-like morphology within the hybrid zone. Backcrosses to R. cyanocarpum were not detected. Therefore F(2)(')s outnumbered all other classes within the hybrid zone, a situation not previously confirmed for plants and extremely rare generally. Hybridization was asymmetrical, with R. delavayi as the maternal parent in all but one of the hybrids detected. ? Conclusions: Although natural hybridization is common in Rhododendron, it is rare in R. cyanocarpum and is apparently not accompanied by backcrossing toward R. cyanocarpum. Hence, there is no immediate risk of genetic swamping, unless habitat disturbance increases and changes the patterns of hybridization. Our study is the first to report a plant hybrid zone dominated by F(2) hybrids. This pattern might contribute to species barrier maintenance.     

Extreme specificity in epiparasitic Monotropoideae (Ericaceae): widespread phylogenetic and geographical structure

The Monotropoideae (Ericaceae) are nonphotosynthetic plants that obtain fixed carbon from their fungal mycorrhizal associates. To infer the evolutionary history of this symbiosis we identified both the plant and fungal lineages involved using a molecular phylogenetic approach to screen 331 plants, representing 10 of the 12 described species. For five species no prior molecular data were available; for three species we confirmed prior studies which used limited samples; for five species all previous reports are in conflict with our results, which are supported by sequence analysis of multiple samples and are consistent with the phylogenetic patterns of host plants. The phylogenetic patterns observed indicate that: (i) each of the 13 plant phylogenetic lineages identified is specialized to a different genus or species group within five families of ectomycorrhizal Basidiomycetes; (ii) mycorrhizal specificity is correlated with phylogeny; (iii) in sympatry, there is no overlap in mature plant fungal symbionts even if the fungi and the plants are closely related; and (iv) there are geographical patterns to specificity.     

中国杜鹃花属的叶表皮特征及其系统学意义

通过光学显微镜和扫描电镜对国产杜鹃花属Rhododendron6个亚属48种4变种植物的叶表皮特征进行观察,结果表明叶表皮的鳞片、腺体、表皮毛的有无和气孔器的类型具有一定的系统学意义。光学显微镜下可见：叶表皮细胞形状为多边形、不规则形,垂周壁式样为较平直、浅波状和波状．气孔器普遍存在于下表皮,上表皮未见气孔器分布,其类型均为无规则形。杜鹃亚属subgen．Rhododendron叶表皮具有鳞片,在扫描电镜下可见气孔器散生于指状突起之间,有别于无鳞类杜鹃花。常绿杜鹃亚属subgen．Hymenanthes和映山红亚属subgen．Tsutsusi有多种不同叶表皮类型;除了凯里杜鹃R．westlandii和弯蒴杜鹃R．henryi形态较特殊之外,马银花亚属subgen．Azaleastrum的马银花组sect．Azaleastrum和长蕊杜鹃组sect．Choniastrum微形态区别不明显。羊踯躅亚属subgen．Pentanthera的羊踯躅R．molle叶表皮有表皮毛,无腺体,气孔器密生,外拱盖形状不对称,外围有多层波形条纹突起可与其他亚属区分：而叶状苞亚属subgen．Therorhodion的叶状苞杜鹃R．redowskianum保卫细胞有明显的T型加厚,与其他亚属种类明显不同,与分子系统发育研究得到的“叶状苞亚属是杜鹃花属的基部类群”的结果吻合。本研究还依据叶表皮微形态特征讨论了一些近缘种类的关系。     

Leaf epidermal features of Rhododendron (Ericaceae)from China and their systematic significance

Rhododendron is the largest genus within the subfamily Rhododendroideae, which has about 1000 known species in the world and more than 500 species in China. Since the genus was established by Linnaeus, its infrageneric relationships have been well studied by many taxonomists on the basis of morphological characters and molecular data. In 1996, Chamberlain et al. proposed a new system of Rhododendron with eight subgenera, i.e., Azaleastrum, Candidastrum, Hymenanthes, Mumeazalea, Pentanthera, Rhododendron, Therorhodion, and Tsutsusi. In this paper, micromorphological characters of leaf epidermis in 4 varieties, 48 species, 6 subgenera of Rhododendron from China were examined using light microscopy (LM) and scanning electron microscopy (SEM). Leaf epidermal features are described and micromorphological types are distinguished here according to morphological characters such as scale, gland, foliar trichome and stomatal apparatus of leaf epidermis. It is shown that the leaf epidermal cells are usually irregular or polygonal in shape. The patterns of anticlinal walls are straight, arched or undulate. The stomatal apparatuses are anomocytic and are usually found on abaxial, not adaxial, epidermis. The results also show that: (1) the lepidote rhododendron (i.e., subgen. Rhododendron), which has both scales and papillae on leaf epidermis, differs distinctly from the elepidote rhododendron; (2) three types of leaf epidermis are identified in subgen. Hymenanthes (i.e., R. fortunei-type, R. chihsinianum-type and R. simiarum-type), whereas four in subgen. Tsutsusi (i.e., R. mariesii-type, R. simsii-type, R. mariae-type and R. flosculum-type); (3) except for R. westlandii and R. henryi, the species of subgen. Azaleastrum show similar morphological characters, i.e., dense stomatal apparatuses surrounded by ringed or discontinuous striates; (4) R. molle of subgen. Pentanthera differs from the species of other subgenera on morphological characters such as foliar trichomes, dense stomatal apparatuses with asymmetrical outer stomatal rims surrounded by undulate-striates, and no gland; (5) only R. redowskianum is found with distinct T-pieces at the polar region of guard cells in Rhododendron. The results support the conclusion inferred from molecular systematic studies that subgen. Therorhodion is the basal clade of Rhododendron. Finally, the relationships between the closely related species are also discussed on the basis of leaf epidermal features.     

Agapetes yingjiangensis (Ericaceae), a new epiphytic species of A. ser. Longifiles from Yunnan,China

Agapetes yingjiangensis (Ericaceae), a new species from Yingjiang County, Yunnan Province, China is described and illustrated. This new species is somewhat similar to A. mannii Hemsl., but differs in having brown‐hirsute young branches, acute mucronate apex of the leaf blade and sparsely hirsute pedicel, calyx tube and corolla. A key to Chinese species with small (less than 2.5 cm) entire leaves in Agapetes sect. Agapetes ser. Longifiles is included.     

中国云南兜兰属（兰科）一新种

20 0 0年 6～ 7月间 ,我们在云南文山、昆明和广西平南等地发现 ,该地生长或栽培的所谓“紫纹兜兰”已经相继开花。而在深圳市梧桐山的紫纹兜兰野生群落每年要到 1 0～ 1 2月左右才开花 ,这就引起我们的注意 ,并对两种不同产地和不同花期的实体进行了较为深入的比较。紫纹兜兰Ｐ .ｐｕｒｐｕｒａｔｕｍ (Ｌｉｎｄｌ.)Ｓｔｅｉｎ的模式标本采自香港 ,在民间被称为“香港小姐”。据说今天在香港地区已较难觅到其芳踪了。 1 990年夏天我们在靠近香港新界的梧桐山上发现了野生的紫纹兜兰居群。它生长在以杜鹃花科、山茶科等植物占优势的乔灌木群…     

A new species of Chirita (Gesneriaceae) from Yunnan,China

A new species of Gesneriaceae, Chirita maguanensis Z.Y.Li, H.Jiang & H.Xu, is described from Southern Yunnan, China. It is similar to C. eburnea Hance in its large, fleshy, white and parallel‐veined bracts, but differs by having broad and oblique leaves with a repand–crenate or crenate margin, suborbicular bracts, membranous, white calyx, purple corolla‐tube, 2‐parted lower lip of stigma and lower disc. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 269–273.     

A new species of Calanthe (Orchidaceae) from Yunnan, China

A new species of Orchidaceae, Calanthe fugongensis X. H. Jin & S. C. Chen, is described and illustrated. The new species is morphologically reminiscent of C. hancockii Rolfe, from which it differs by having hamate lateral lobes, and an elliptical middle lobe with three rectangular lamellae.     

Rhododendron kuomeianum (Ericaceae), a new species from northeastern Yunnan (China), based on morphological and genomic data

Rhododendron kuomeianum Y.H. Chang, J. Nielsen & Y.P. Ma, a new species of Rhododendron (Ericaceae) within subsect. Maddenia in sect. Rhododendron from Yiliang County, NE Yunnan, China, is described and illustrated. The new species is similar to R. valentinianum, but it can be easily distinguished by its sparse scales on the abaxial surface of the leaf blade, fewer flowers per inflorescence and white corolla with pale red margins. There are also differences in the widths of calyx lobes, leaf blade shape and indumentum characteristics of the petiole between the new species and Rhododendron linearilobum. We confirmed that R. kuomeianum is a new species closely related to R. valentinianum and R. changii with phylogenomic studies of 10 species within this subsection based on restriction site-associated DNA sequencing (RAD-seq) data. These phylogenomic analyses also clarified additional taxonomic problems in this subsection previously raised by morphological analysis. Our findings make a strong case for using next-generation sequencing to explore phylogenetic relationships and identify new species, especially in plants groups with complicated taxonomic problems.     

Molecular phylogeny of the Monotropoideae (Ericaceae) with a note on the placement of the Pyroloideae

Mycotrophism occurs in two ericaceous subfamilies, the Monotropoideae and the Pyroloideae. However, three aspects of the evolution of these subfamilies remain equivocal; 1) morphological, biochemical, and molecular analyses have failed to establish that the Monotropoideae is monophylectic; 2) the relationships among members of the Monotropoideae remain unresolved; 3) it is unclear whether the Pyroloideae should be included as a subfamily within the Ericaceae or treated as a separate family. To address these topics a phylogeny was constructed using a portion of the 28S ribosomal RNA gene from 22 members of the Ericaceae. Results indicate that the present Monotropoideae is polyphyletic; one species, Monotropsis ordata, is more closely related to members of the Vaccinioideae than to the rest of the Monotropoideae. This arrangement is supported by consideration of mycorrhizal type, consequently multiple origins of mycotrophic parasitism must be assumed. The relationships depicted within the Monotropoideae are nearly congruent with those depicted in Copeland's (1941) phylogeny, and morphological or biochemical characters are identified which support the relationships depicted by the molecular tree which do not agree with the morphological tree. In addition, the data indicate, although not strongly, that the Pyroloideae should be included within the Ericaceae.     

A new species of Comarostaphylis (Ericaceae,Arbuteae) from Tamaulipas,Mexico

Comarostaphylis sharpii is described from the vicinity of Rancho del Cielo near Gómez Farías in the Sierra de Guatemala of southwestern Tamaulipas, Mexico. It occurs in a narrow zone of Humid Pine-Oak Forest at elevations between 1200 and 2100 m.     

中国贵州杜鹃属两新种

报道了中国贵州杜鹃属植物2新种--枇杷叶杜鹃(Rhododendron eriobotryoides Xiang Chen & Jia Y.Huang)和金波杜鹃(R.jinboense Xiang Chen & X.Chen).枇杷叶杜鹃与皱叶杜鹃(R.denudatum)相似,但本种叶背毛被较薄而稀疏,花丝基部密被微柔毛,花柱通体被腺体.金波杜鹃与短脉杜鹃(R.brevinerve)相似,但前者的叶长圆状椭圆形,叶片上卷呈U形,花序具较多花,花冠较长,花丝基部密被微柔毛,子房密被绒毛.目前,仅发现2新种各有1个含数株的种群,资源量十分稀少,依据IUCN红色名录标准均属于极危物种(CR),需要加以重点保护.     

A distinctive new species of Viola (Violaceae) from Yunnan, China

A new species of Viola (Violaceae) from north-western Yunnan, China, is described and illustrated. Viola dimorphophylla Y. S. Chen & Q. E. Yang sp. nov. is endemic to Zhongdian County, north-western Yunnan, and is very easily distinguishable from all other Chinese species of the genus by having obviously dimorphic leaves, with the basal ones being long petiolate, undivided and widely cordate, and the cauline ones sessile, linear and verticillate.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 115–119.     

Mycorrhizal fungal community composition in seven orchid species inhabiting Song Mountain,Beijing, China

Mycorrhizal fungi play an important role in the germination and growth of orchids essentially influencing their survival,abundance, and spatial distribution. In this study, we investigated the composition of the mycorrhizal fungal community in seven terrestrial orchid species inhabiting Song Mountain, Beijing, China, using Illumina MiSeq high-throughput sequencing. The mycorrhizal communities in the seven orchids were mainly composed of members of the Ceratobasidiaceae, Sebacinales, and Tulasnellaceae, while a number of ectomycorrhizal fungi belonging to the Russulaceae, Tricholomataceae, Thelephoraceae, and Cortinariaceae were occasionally observed. However, the dominant fungal associates and mycorrhizal community differed significantly among the orchid species as well as subhabitats. These findings confirm the previous observation that sympatric orchid species show different preferences for mycorrhizal fungi, which may drive niche partitioning and contribute to their cooccurrence.