首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 21 毫秒
1.
Some remarkable mosses, as a result of the study of both recent collections and a review of herbarium specimens, are reported in this paper. They are: Anomodon rugelii (Müll.Hal.) Keissl., new record from southern Italy, a moss very rare in the Mediterranean region and considered threatened in many European countries; Blindia acuta (Hedw.) Bruch & Schimp. and Dichodontium palustre (Dicks.) M. Stech, both new records from Sicily, are very rare mosses in Italy. Moreover, a new locality in Sicily for the little-known species Tortula bolanderi (Lesq. & James) M. Howe is reported.  相似文献   

2.
Paramesopsocus lu n. gen., n. sp. and Paramesopsocus adibi n. sp. are respectively described from the Early Cretaceous amber of Lebanon and from the Late Jurassic limestone of Karatau (Kazakhstan). They are placed within the suborder Psocomorpha, and in the Mesozoic extinct family Paramesopsocidae n. fam. A cladistic phylogeny for Psocomorpha is given including our fossil taxa. The discovery of these new taxa demonstrates the necessity of a deep cladistic redefinition of the currently admitted major subdivisions of this suborder.  相似文献   

3.
Analysis of 66 samples from DSDP Site 263 (Cores 263-4R-4 to 263-29R-4) reveals a unique faunal composition with a predominance of agglutinated taxa, many of them previously unrecorded from any other DSDP and ODP Indian Ocean sites. A total of 66 agglutinated and 31 calcareous taxa are documented and five new species are described: Hippocrepina gracilis n.sp., “Textulariopsiselegans n.sp., Aaptotoichus challengeri n.sp., “Gaudryinopsispseudobettenstaedti n.sp. and “Gaudryinacuvierensis n.sp. Three assemblages are recognized based on changes in the composition of dominant taxa and occurrences of stratigraphically important species: (1) a high-diversity Valanginian to Barremian Bulbobaculites-Recurvoides Assemblage (Cores 263-29R to -18R), comprised of numerous elongate agglutinated forms, rare nodosariids, and variable numbers of tubes and ammodiscids; (2) a moderately diverse Aptian to Albian Rhizammina-Ammodiscus-Glomospira Assemblage (Cores 26318R to -7R) with highly fluctuating numbers of the nominate taxa and Haplophragmoides, Trochammina, Verneuilinoides spp., and Vemeuilina howchini; (3) a very low diversity Albian or younger Assemblage (Cores 263-6R to -4R) containing sparse agglutinated foraminifera, rare nodosariids and rotaliids. We interpret the assemblages as shelf to lower slope and consider them to reflect a deepening palaeobathymetry as the Cuvier margin subsided after the initial breakup of East Gondwana during the Valanginian. Our interpretation is in sharp contrast with initial palaeodepth estimates of less than 100 m, as well as with original chronostratigraphic interpretations based on foraminifera and nannofossils which correlated the base of the recovered interval with the Aptian. The absence of many cosmoplitan forms, despite high diversity, suggests strong faunal differentiation in the Austral realm or endemisn within the Cuvier Basin during the Early Cretaceous.  相似文献   

4.
5.
Abstract

Teleosauroids were a clade of semi-marine crocodylomorphs that attained near-global distribution during the Jurassic Period. They were particularly common during the Toarcian (Early Jurassic) and are well documented throughout the UK and Germany. However, Toarcian teleosauroids discovered in Luxembourg have been little studied and rarely discussed in the scientific literature. Here we present a comprehensive catalogue of Luxembourg thalattosuchian specimens, including nine teleosauroids (all from the Toarcian) and five Thalattosuchia indeterminate (four from the Toarcian and one from the Bajocian), many of which are noted in the literature for the first time. We describe these specimens and identify two distinct genera (Steneosaurus and Platysuchus) as present in the sample as well as three, or possibly four, distinct species. This represents a high diversity of teleosauroid taxa (both common and rare forms) from the Toarcian rarely seen elsewhere in the world.  相似文献   

6.
Abstract

A newly discovered track in the Chinle Group north of Moab, Utah, is attributable to the ichnogenus Atreipus, an ichnotaxon that is relatively common in eastern North America (Newark Supergroup) but very rare in the Late Triassic of the western part of the continent. This is only the second report of the genus from the Chinle Group. Atreipus has been attributed to a silesaurid dinosauriform, and dinosauriform taxa are relatively abundant by skeletal material in the Late Triassic of western North America, but track evidence in the same units is dominated by ichnotaxa attributed to dinosaurs. The rarity of Atreipus is currently an anomaly in the region.  相似文献   

7.
8.
Abstract

The present study focused on the bryoflora of watercourses of the Tiber River basin watercourses (Central Italy). A total of 20 bryophyte species, which included 14 mosses and 6 liverworts, were collected at 32 river stations. Most species were recorded at stations of the watercourses' upper sections, which have rocky substrate and where there is cool and well oxygenated running water, with low trophic load. Only few species, such as Leptodictyum riparium, Cinclidotus fontinaloides and Riccia fluitans, were also found at stations of the middle and lower sections, which are characterized by slow-flowing, turbid, warm and eutrophic waters. Some species are widely distributed, among which Fontinalis antipyretica ssp. antipyretica and Platyhypnidium riparioides, while others are very rare, such as Cinclidotus aquaticus, Dialytrichia mucronata and R. fluitans. Some of the collected species are new regional records (Hygroamblystegium fluviatile, D. mucronata), regional confirmations of rare taxa in Italy (C.aquaticus) or confirmations of old regional reports (Hygroamblystegium tenax, C. fontinaloides, Aneura pinguis).  相似文献   

9.
Abstract

The new gammarideans Photis nigrocula, P. phaeocula, and Halice sublittoralis are described from grab samples taken from the North Arm of Port Pegasus, where they appear to be the most abundant amphipods on the sandy-mud substrate. They are illustrated and compared with closely related taxa.  相似文献   

10.
Abstract

A contribution to the fossil Silicoflagellates of the late Miocene in Central Italy. - A microscopic analysis of fourteen diatomite samples from a Messinian (late Miocene) stratigraphic series, in central-eastern Italy, has been carried out in order to verify the presence of Silicoflagellates. The skeletons of eight taxa were found in good condition and identified. The most abundant and continuous in the stratigraphic series examined are Dictyocha fibula and Distephanus speculum, also known in the present-day seas; Cannopilus sphaericus, a very rare and interesting species extinct in the Miocene, is limited to only two samples. On the basis of the Silicoflagellates found, it is possible to suggest that they lived in an open sea with 30–40‰ salinity and a temperature of 10–20°C. A very similar situation is present nowadays in the middle-western Adriatic Sea.  相似文献   

11.
Dugan  F. M.  Lupien  S. L. 《Mycopathologia》2003,156(1):31-40
Asymptomatic seeds of forage and weedy grasses from germplasm accessions and from uncultivated sites in eastern Washington and western Idaho were assayed for the presence of quiescent filamentous fungi. Asymptomatic culm nodes of the same species were similarly assayed. The predominant taxa isolated were strains of dematiaceous hyphomycetes, principally strains of Alternaria and Cladosporium. A. infectoria was the species most frequently isolated from seed. A. tenuissima was common and A. alternata was rare. Aspergillus, Penicillium and Fusarium were very rare or absent in stored germplasm. Pathogenic coelomycetes were common in asymptomatic node samples, occasionally present in asymptomatic field seed, but were not detected in germplasm accessions. Previous reports of frequent occurrence of A. alternata in grass seed are probably the results of misidentification of various small-spored Alternarias, especially A. infectoria, as A. alternata.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

12.
13.
Interspecific hybridization and polyploidy are pivotal processes in plant evolution and speciation. The fate of new hybrid and polyploid taxa is determined by their ability to reproduce either sexually or asexually. Hybrids and allopolyploids with odd chromosome numbers are frequently sterile but some establish themselves through asexual reproduction (vegetative or apomixis). This allows novel genotypes to become established by isolating them from gene flow and leads to complex patterns of variation. The genus Sorbus is a good example of taxonomic complexity arising from the combined effects of hybridization, polyploidy and apomixis. The Avon Gorge in South‐west Britain contains the greatest diversity of Sorbus in Europe, with three endemic species and four putative endemic novel hybrids among its 15 native Sorbus taxa. We used a combination of nuclear microsatellite and chloroplast DNA markers to investigate the evolutionary relationships among these Sorbus taxa within the Avon Gorge. We confirm the genetic identity of putative novel taxa and show that hybridization involving sexual diploid species, primarily S. aria and S. torminalis and polyploid facultative apomictic species from subgenus Aria, has been responsible for generating this biodiversity. Importantly our data show that this creative evolutionary process is ongoing within the Avon Gorge. Conservation strategies for the rare endemic Sorbus taxa should therefore consider all Sorbus taxa within the Gorge and must strive to preserve this evolutionary process rather than simply the individual rare taxa that it produces.  相似文献   

14.
Understanding of the biology of rarity is central to the conservation of some endangered species. Rare taxa are often reported to be specialized, but they are usually poorly studied. The Ethiopian wolf (Canis simensis) is endemic to the Ethiopian highlands and in two major populations, Bale and Arsi in the southern range of the species, it preys almost exclusively upon diurnal rodents all year round, mainly molerats Tachyoryctes macrocephalus and common molerats T. splendens, respectively. Where these large rodents are absent or rare, wolves are expected to rely more heavily on nocturnal rats or livestock. Prey remains in 161 scats from five newly studied populations confirmed that wolves are indeed specialist rodent hunters elsewhere, and that their narrow diets are dominated by diurnal Murinae rats (60–83% of prey occurrences). Swamp rats Otomys typus were the main prey, followed by grass rats Arvicanthis abyssinicus. Common molerats, Lophuromys rats and nocturnal Stenocephalemys spp. constituted the variable portion of the diets, and their proportional contributions varied across populations in relation to elevation and latitude. Towards the north, where the climate is drier and human populations more dense, wolves predate more frequently on rat‐sized prey, including nocturnal species, with implications for the survival of small populations in the Northern Highlands.  相似文献   

15.
Seventy-five bryozoan species were picked from shallow bottom sediments (0–33 m depths) at five sites in the northern Red Sea: El Fanader, Hurghada Harbour, Makkadi Bay, Al Qweh Lagoon and El-Humrawen. Crisia specimens (Cyclostomata) are common and exhibit different variations. Six species were recognised among the specimens collected: Crisia eburnea (Linnaeus), Crisia elongata (Milne-Edwards), Crisia hornesi Reuss, Crisia sertularoides (Audouin), Crisia tenuis MacGillivray and Crisia hurghadaensis n. sp. The present paper deals with these Crisia species; other bryozoan taxa recovered will be published later. Biogeographic study reveals that three of these species are cosmopolitan, and represented by common to abundant occurrences (C. elongata, C. eburnea and C. hornesi). Two species are local endemics, and represented by only rare occurrences (C. sertularoides and C. hurghadaensis n. sp.). One species (C. tenuis) is Indo-Pacific, and is recorded here for the first time in equatorial waters.  相似文献   

16.
In this work, they compared patterns of abundant and rare picoeukaryotic sub‐communities in the epipelagic waters (surface and 40–75 m depth subsurface layers) of the East and South China Seas across seasons via 454 pyrosequencing of the V4 region of 18S rDNA. They also examined the relative effects of environmental filtering, dispersal limitations and seasonality on community assembly. Their results indicated that (i) in the surface layer, abundant taxa are primarily influenced by dispersal limitations and rare taxa are primarily influenced by environmental filtering, whereas (ii) in the subsurface layer, both abundant and rare sub‐communities are only weakly influenced by environmental filtering but are strongly influenced by dispersal limitations. Moreover, (iii) abundant taxa exhibit stronger temporal variability than rare taxa. They also found that abundant and rare sub‐communities display similar spatial richness patterns that are negatively correlated with latitude and chlorophyll a and positively correlated with temperature. In summary, environmental filtering and dispersal limitations have different effects on abundant and rare picoeukaryotic sub‐communities in different layers. Thus, depth appears as an essential variable that governs the structuring patterns of picoeukaryotic communities in the oceans and should be thoroughly considered to develop a more comprehensive understanding of oceanic microbial assemblages.  相似文献   

17.
Based on morphological and molecular data, calcareous dinoflagellates (Thoracosphaeraceae, Peridiniales) are a monophyletic group comprising the three major clades Ensiculifera/Pentapharsodinium, Thoracosphaera/Pfiesteria, and Scrippsiella sensu lato. We used stratigraphically well‐documented first occurrences of particular archeopyle types to constrain relaxed Bayesian molecular clocks applied to nuclear rRNA sequences of 18 representatives of the three main clades. By comparing divergence estimates obtained in differently calibrated clocks with first stratigraphic occurrences of taxa not themselves used as constraints, we identified plausible divergence times for several subclades of calcareous dinoflagellates. The initial diversification of extant calcareous dinoflagellates probably took place in the Late Jurassic, with the three main clades all established by the Cretaceous. The two mesoepicystal operculum types observed in calcareous dinoflagellates probably evolved independently from simple apical archeopyles. Based on our taxon sample, the K/T boundary had relatively little effect on the diversity of the group, with several lineages dating to before 65 mya (million years ago). The first stratigraphic occurrences of key taxa, such as Thoracosphaera and Calciodinellum (not themselves used as constraints), are in agreement with the molecular time estimates. Conflicts that involve “Calciodinellumlevantinum, Leonella, Pentapharsodinium, Pernambugia, and the Scrippsiella trochoidea species complex may be due to inaccurate assignment of fossils because of high morphological homoplasy and insufficient knowledge of the extant diversity of calcareous dinoflagellates.  相似文献   

18.
Desmids from 12 freshwater resources in the northern part of Thailand were investigated during 2002 to 2003. A total of 91 taxa were found. They belonged to 17 genera: Actinotaenium, Spirotaenia, Netrium, Gonatozygon, Pleurotaenium, Closterium, Euastrum, Micrasterias, Cosmarium, Cosmocladium, Stuarastrum, Staurodesmus, Xanthidium, Teilingia, Spondylosium, Hyalotheca and Desmidium. The water qualities in all the water resources were classified as oligotrophic to meso-eutrophic by trophic status. The taxa that could possibly be used as bioindicators of trophic state were Staurastrum gutwinskii, Spondylosium pandurifoemae, Cosmarium capitulum, C. mediosrobiculatum var. egranutum, S. tortum, Closterium gracile var. elongatum, C. kuetzingii and Closterium dianae var. dianae. The most frequently found taxa were Staurastrum limneticum var. burmense, S. tetracerum var. tetraerum, Pleurotaenium trabecula, Closterium ehrenbergii var. ehrenbergii and C. kuetzingii. The rare taxa in this study were Actinotaenium sp. Spirotaenia condensata, Pleurotaenium burmense var. dacchense and Micrasterias apiculata. Forty-one taxa of desmids were identified as new records for Thailand. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.  相似文献   

19.
20.
Abstract

Some taxa of Sicilian Helichrysum related to sect. Stoeachadina have an uncertain systematic position; moreover, they are rare and endangered. In order to preserve these taxa in a genebank, a strategy to keep their genetic variation as high as possible is required. The high informative content of AFLP markers was used to assess genetic variations within and between populations and their relationships. The results show that all populations are genetically similar, even though there are two distinct groups: the first is the population referred to H. pendulum, and the second is represented by other populations belonging to several different specific and intraspecific taxa. The H. pendulum population is homogeneous, and characterised by the lowest genetic variation among all the populations considered. The second group shows a greater variation as evidenced by the presence of three subgroups: (i) populations referred to H. panormitanum var. panormitanum and H. panormitanum var. stramineum, (ii) populations referred to H. errerae var. errerae and H. errerae var. messerii, (iii) a population referred to H. hyblaeum, which, despite morphological and chorological differences, is similar to the other populations of the second group from a genetic stand point. Each population of the above-mentioned taxa has local fragment markers whose frequency is useful to determine how many plants should be sampled in order to collect the seeds necessary to preserve the population's genetic diversity in a genebank.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号