共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Three years of studies on some Indian Himalayan rivers in Jammu & Kashmir, Himachal Pradesh, and Sikkim revealed the presence
of Didymosphenia geminata (Lyngbye) M. Schmidt, a large diatom, hitherto unreported from these areas. This is first report on the occurrence of this
diatom in some Indian Himalayan rivers: Kishanganga in Jammu & Kashmir, Ravi in Himachal Pradesh in Western Himalaya and in
Teesta river and its two tributaries, Lachen Chhu and Lachung Chhu from Sikkim in the Eastern Himalaya. D. geminata is the most abundant taxon in both suspended and benthic algal communities in these rivers. The species exhibits wide ecological
amplitude, allowing it to inhabit both cold and warm waters. We also recorded the exotic brown trout, Salmo
trutta
fario in these Himalayan rivers. However, in Central Himalayan rivers, Alaknanda, Bhilangana, Mandakini and Dhauliganga in Uttarakhand,
where this diatom was absent the trout were absent too. Our studies indicate that D. geminata may extend its distribution range to other Himalayan rivers, hitherto uninhabited by the diatom, depending on the mode of
introduction of exotic trout in these rivers. 相似文献
3.
Corydalis hamata Franch. is described and illustrated. Variation within the species and relationships with related species are discussed. Corydalis pseudohamata Fedde is reinstated as a species. 相似文献
4.
Seven species of the genus Cosmospora collected in Japan are reported in this article. Among them, Cosmospora japonica is described as a new species. Cosmospora henanensis, C. rishbethii, and C. triqua, all of which are known only from their type localities, are added to the Japanese mycobiota. The other species, C. chaetopsinaecatenulatae, C. diminuta, and C. peponum, are new records for Japan. Additional distribution records are given for Cosmospora species hitherto known in Japan. 相似文献
5.
Interspecific competition amongst parasitoids is important in shaping the evolution of life‐history strategies in these insects as well as community structure. Competition for hosts may occur between adult female parasitoids (‘extrinsic’ competition) or their progeny (‘intrinsic’ competition). Here, we examined intrinsic competition between two solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis in cocoons of a primary parasitoid, Cotesia glomerata. Each species was allowed to sting hosts previously parasitized by the other at 24 h time intervals over the course of 144 h (6 days). When hosts were attacked simultaneously, neither species was dominant although the species to attack first won most encounters when it had a 24–48 h head start. However, after this time there was dramatic shift in the outcome with G. agilis dominating in all hosts > 72‐h old, regardless of which species had parasitized C. glomerata first. G. agilis larvae, which initially had competed with L. nana for control of C. glomerata resources, began attacking the larvae of L. nana, whereas L. nana rejected hosts with older G. agilis larvae or pupae. Effects of multiparasitism also affected the development time and adult mass of the winning parasitoid. Our results reveal a shift in the trophic status of G. agilis from C. glomerata (in younger hosts) to L. nana (in older hosts), the first time such a phenomenon has been reported in parasitoids. 相似文献
6.
Martyn Rix 《Curtis's Botanical Magazine》2004,21(3):189-192
Summary. A rare bramble from the eastern Himalaya, Rubus calophyllus C.B. Clarke is illustrated. Its distribution and habitat are described and related species are discussed. 相似文献
7.
Marcos José da Silva Allan Carlos Pscheidt Inês Cordeiro 《Nordic Journal of Botany》2016,34(3):364-369
Microstachys crassifolia, a new species from Chapada dos Veadeiros region in the State of Goias, central Brazil, is here described and illustrated. Its habit and general morphology resembles that of M. nana Silva & Esser, an endemic species from the State of Paraná, southern Brazil. Both species are hemicryptophytes from grasslands, with a well‐developed underground system, glabrous leaves and reddish inflorescences and fruits, but M. crassifolia has fleshy leaves without glands while M. nana has membranaceous leaves with pateliform, submarginal glands. 相似文献
8.
Two endangered new species of Marsdenia R. Br. (Asclepiadoideae, Apocynaceae) from the semi-arid region of Brazil are described and illustrated: M. breviramosa (south-western Bahia) and M. nana (northern Minas Gerais). They are shrubs closely related to M. zehntneri and, like that species, are also associated with calcareous outcrops. The former can be recognised by linear leaves arranged
in small, compact shoots and the latter is a subshrub less than 50 cm high whose flowers are unique because of the adaxially
villous corolla and long-rostrate gynostegium. 相似文献
9.
Studies on the Alocasia clade (Araceae) of Peninsular Malaysia I: Alocasia farisii sp. nov. from limestone in Kelantan
下载免费PDF全文
![点击此处可从《Nordic Journal of Botany》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alocasia farisii Zulhazman, Norzielawati & P. C. Boyce is described and illustrated from Karst limestone in Kelantan as the first recorded Peninsular Malaysian species of the hitherto wholly Bornean Alocasia princeps complex, within which A. farisii most closely resembles the southwest Sarawak limestone‐obligated Alocasia reversa N. E. Br. 相似文献
10.
11.
在近期缅甸北部的植物考察中,一种菌类寄生植物矮生喜荫草(Sciaphila nana Blume)被发现和确认。矮生喜荫草代表缅甸被子植物一新记录科,霉草科植物。矮生喜荫草主要特征为花单性同株、雄花内轮花被片顶端具有柄的门把状物、花被片6、3个雄蕊、花药4室。 相似文献
12.
Hiroshi Takahashi 《Journal of plant research》1987,100(2):185-203
The floral and pollination biology of three closely related species,Tricyrtis flava, T. nana andT. ohsumiensis, were comparatively investigated. The primary pollinator wasBombus diversus in all the three species observed, andAmegilla sp. also acted forT. ohsumiensis. The flowers ofT. flava andT. ohsumiensis bloom for two days and are protandrous. Thus autogramy seems to be prevented in these species when the larger bees forage
on them, though geitonogamy may also occur. On the other hand,T. nana appears to be a primarily self-pollinating species. The flowers of this species open only during one day and are homogamy.
The stigmata seem to receive much pollen of their own flower by the visit of bumblebees. Moreover, many flowers ofT. nana fruited without any visit of pollinators.T. nana has many features characterizing the autogamous derivatives. 相似文献
13.
Aletris simpliciflora R. Li & S. D. Zhang, a new species of Nartheciaceae from southwest Xizang, China, is described and illustrated. It is similar, and apparently closely related, to A. nana S. C. Chen, but differs by having usually solitary flower, pubescent bract and bracteole, and distinct filaments ca 1.2 mm long. 相似文献
14.
Tuguo Tateoka 《Journal of plant research》1977,90(2):103-128
Morphological and pollen studies were made for the collections belonging toCalamagrostis langsdorffii, C. Sachalinensis, C. longiseta, C. nana and various intermediates between these species from central Honshu, the chromosome numbers of which were reported in a previous
paper (Tateoka, 1976). Additional collections made from the Akaishi Range in 1976 were also subjected to the present work.
The intermediates showed 0%, or nearly 0%, pollen stainability and a mosaic of morphological features of putative parental
taxa which can be estimated to occur for F1 hybrids. This estimation was sustained by a comparison with the pattern of character expressions for the artificially raised
F1 hybrids of various European species ofCalamagrostis as reported by Nygren (1962). These results as well as field observations strongly suggested that the intermediates may be
wholly or almost wholly F1 hybrids. The hybrids were sometimes found in abundance within a limited area, but seemed to have little capacity to migrate
from the places where they originated. The following combinations, which were not previously recorded, were disclosed:C. longiseta×C. sachalinensis, C. langsdorffii×C. nana, C. langsdorffii×C. longiseta, C. longiseta×C. nana. Possibilities of introgression in these hybridizing species were discussed. The hybrids were tetraploids except one hexaploid
which was discovered in a mixed population ofC. nana, C. longiseta and their putative F1 hybrids at the tetraploid level. The hexaploid in question, which seemed to have resulted from the participation of an unreduced
gamete, was very similar morphologically toC. nana subsp.hayachinensis distributed in the mountain far distant from central Honshu. Geographical distributions of the hybrid plants were surveyed
through examination of the herbarium specimens. 相似文献
15.
Jeffrey A. Harvey 《Evolutionary ecology》2008,22(2):153-166
In most animals, the optimal phenotype is determined by trade-offs in life-history traits. Here, I compare development and
reproductive strategies in two species of solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis, attacking pre-pupae of their primary parasitoid host, Cotesia glomerata. Parasitoid larvae of both species exploit a given amount of host resources with similar efficiency. However, adults exhibit
quite different reproductive strategies. Both species are synovigenic, and female wasps emerge with no mature eggs. However,
G. agilis must first host-feed to produce eggs, while L. nana does not host-feed but mobilizes internal resources carried over from larval feeding to initiate oogenesis. Further, G. agilis is wingless, produces large eggs, has a long life-span, and generates only small numbers of progeny per day, whereas these
traits are reversed in L. nana. Given unlimited hosts, the fecundity curve in L. nana was “front-loaded,” whereas in G. agilis it was depressed and extended over much of adult life. In L. nana (but not G. agilis), wasps provided with honey but no hosts lived significantly longer than wasps provided with both honey and hosts. Differences
in the fecundity curves of the two hyperparasitoids are probably based on differing costs of reproduction between them, with
the wingless G. agilis much more constrained in finding hosts than the winged L. nana. Importantly, L. nana is known to be a specialist hyperparasitoid of gregarious Cotesia species that pupate in exposed locations on the food plant, whereas Gelis sp. attack and develop in divergent hosts such as parasitoid cocoons, moth pupae and spider egg sacs. Consequently, there
is a strong match between brood size in C. glomerata and egg production in L. nana, but a mismatch between these parameters in G. agilis. 相似文献
16.
Sinningia lutea (Gesneriaceae) is described and illustrated as a new species from the Pampa Biome, in Southern Brazil. In the literature, this species has hitherto been confused with S. allagophylla from which it can be easily separated using a set of floral and vegetative features (especially corolla color and size and leaf shape). An artificial key to separate S. lutea from S. allagophylla and S. curtiflora (another sympatric species, with some morphological similarities) is presented. Some ecological remarks on the differential distribution of S. lutea and S. allagophylla are also made. 相似文献
17.
Comparative analyses of plastid and AFLP data suggest different colonization history and asymmetric hybridization between Betula pubescens and B. nana
下载免费PDF全文
![点击此处可从《Molecular ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pernille Bronken Eidesen Inger Greve Alsos Christian Brochmann 《Molecular ecology》2015,24(15):3993-4009
Birches (Betula spp.) hybridize readily, confounding genetic signatures of refugial isolation and postglacial migration. We aimed to distinguish hybridization from range‐shift processes in the two widespread and cold‐adapted species B. nana and B. pubescens, previously shown to share a similarly east–west‐structured variation in plastid DNA (pDNA). We sampled the two species throughout their ranges and included reference samples of five other Betula species and putative hybrids. We analysed 901 individual plants using mainly nuclear high‐resolution markers (amplified fragment length polymorphisms; AFLPs); a subset of 64 plants was also sequenced for two pDNA regions. Whereas the pDNA variation as expected was largely shared between B. nana and B. pubescens, the two species were distinctly differentiated at AFLP loci. In B. nana, both the AFLP and pDNA results corroborated the former pDNA‐based hypothesis that it expanded from at least two major refugia in Eurasia, one south of and one east of the North European ice sheets. In contrast, B. pubescens showed a striking lack of geographic structuring of its AFLP variation. We identified a weak but significant increase in nuclear (AFLP) gene flow from B. nana into B. pubescens with increasing latitude, suggesting hybridization has been most frequent at the postglacial expansion front of B. pubescens and that hybrids mainly backcrossed to B. pubescens. Incongruence between pDNA and AFLP variation in B. pubescens can be explained by efficient expansion from a single large refugium combined with leading‐edge hybridization and plastid capture from B. nana during colonization of new territory already occupied by this more cold‐tolerant species. 相似文献
18.
Nian Wang James S. Borrell William J. A. Bodles Anasuya Kuttapitiya Richard A. Nichols Richard J. A. Buggs 《Molecular ecology》2014,23(11):2771-2782
Past reproductive interactions among incompletely isolated species may leave behind a trail of introgressed alleles, shedding light on historical range movements. Betula pubescens is a widespread native tetraploid tree species in Britain, occupying habitats intermediate to those of its native diploid relatives, B. pendula and B. nana. Genotyping 1134 trees from the three species at 12 microsatellite loci, we found evidence of introgression from both diploid species into B. pubescens, despite the ploidy difference. Surprisingly, introgression from B. nana, a dwarf species whose present range is highly restricted in northern, high‐altitude peat bogs, was greater than introgression from B. pendula, which is morphologically similar to B. pubescens and has a substantially overlapping range. A cline of introgression from B. nana was found extending into B. pubescens populations far to the south of the current B. nana range. We suggest that this genetic pattern is a footprint of a historical decline and/or northwards shift in the range of B. nana populations due to climate warming in the Holocene. This is consistent with pollen records that show a broader, more southerly distribution of B. nana in the past. Ecological niche modelling predicts that B. nana is adapted to a larger range than it currently occupies, suggesting additional factors such as grazing and hybridization may have exacerbated its decline. We found very little introgression between B. nana and B. pendula, despite both being diploid, perhaps because their distributions in the past have rarely overlapped. Future conservation of B. nana may partly depend on minimization of hybridization with B. pubescens, and avoidance of planting B. pendula near B. nana populations. 相似文献
19.
Lilja Karlsdóttir Ægir Th. Thórsson Margrét Hallsdóttir Adalsteinn Sigurgeirsson Thröstur Eysteinsson 《Grana》2013,52(2):78-84
Subfossil pollen from two co‐existing Betula species in Iceland, B. nana and B. pubescens, is frequently found in sediments and peat. Interpretation of the findings often depends on the ability to differentiate between the two species according to pollen size and structure. Fresh pollen samples were prepared from 70 individual trees/shrubs which had been identified to species by chromosome number. Grain diameters and pore depths were measured and ratios of grain diameter to pore depth (D/P ratios) were calculated. The mean grain diameters of pollen from diploid B. nana and tetraploid B. pubescens were 20.42 and 24.20?µm, whereas mean pore depths were 2.20 and 2.81?µm respectively. Mean D/P ratios were therefore 9.55 for B. nana and 8.85 for B. pubescens. The difference between species was statistically significant for all three pollen parameters. Grain diameter appeared to be the most useful parameter, as only about 20% of the samples were in the overlapping region of the species distributions. Pollen size (grain diameter) was also positively correlated to tree morphology, which was evaluated using species‐specific botanical characters. Pollen samples from different locations/populations in Iceland varied slightly in mean size and ratio. The size difference between pollen of B. nana and B. pubescens in this study is less than other papers have reported, which may be due to the effect of introgressive hybridisation between the two birch species in Iceland. 相似文献
20.
Two new species in the Chaetoceros socialis complex (Bacillariophyta): C. sporotruncatus and C. dichatoensis,and characterization of its relatives,C. radicans and C. cinctus
下载免费PDF全文
![点击此处可从《Journal of phycology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chetan C. Gaonkar Wiebe H. C. F. Kooistra Carina B. Lange Marina Montresor Diana Sarno 《Journal of phycology》2017,53(4):889-907
The diatom genus Chaetoceros is one of the most abundant and diverse phytoplankton in marine and brackish waters worldwide. Within this genus, Chaetoceros socialis has been cited as one of the most common species. However, recent studies from different geographic areas have shown the presence of pseudo‐cryptic diversity within the C. socialis complex. Members of this complex are characterized by curved chains (primary colonies) aggregating into globular clusters, where one of the four setae of each cell curves toward the center of the cluster and the other three orient outwards. New light and electron microscopy observations as well as molecular data on marine planktonic diatoms from the coastal waters off Chile revealed the presence of two new species, Chaetoceros sporotruncatus sp. nov. and C. dichatoensis. sp. nov. belonging to the C. socialis complex. The two new species are similar to other members of the complex (i.e., C. socialis and C. gelidus) in the primary and secondary structure of the colony, the orientation pattern of the setae, and the valve ultrastructure. The only morphological characters that can be used to differentiate the species of this complex are aspects related to resting spore morphology. The two newly described species are closely related to each other and form a sister clade to C. gelidus in molecular phylogenies. We also provide a phylogenetic status along with the morphological characterization of C. radicans and C. cintus, which are genetically related to the C. socialis complex. 相似文献