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 15 毫秒
1.
Summary The distinctive peridial appendages ofArthroderma were of little value for the delimitation of species. The peridial appendages as well as the conidia of certain species were so similar as to be value-less for the delimitation of species. Further, morphological and physiological variation was found to be as great within, as between, species. The usual morphological methods for classifying species were, therefore, inadequate and the concept of biological species was considered.The following points were found to favor the applicability of biological species concepts. Nine of ten species were heterothallic which assured crossing. A gene pool, the result of sexual reproduction and an essential requirement of a biological species, was maintained. This was evidenced by complete fertility between isolates of the same species from diverse geographic areas. Finally, no hybridization between species was evident in over one hundred attempted crosses.Strains which were readily compatible and produced viable ascospores were considered to be members of the same species. Conversely, incompatible strains were differentiated into separate species. In this way over fifty strains from more than one hundred isolations were found to be members of ten species. Six of the species correlated with species previously described on morphological bases, and confirmed their validity. Four species were considered to be new. All four were previously confused withA. quadrifidum orA. cuniculi because they possessed similar types of conidia. Once separated on an incompatibility basis, they were found to possess characteristics of distinct species. The only reliable method for their differentiation, however, was found to be interspecific incompatibility.Several strains, some pathogens, were crossed with soil borne species ofArthroderma. Some mated but others did not. Several incompatible strains possessedArthroderma-like appendages and partial compatibility was indicated. Partial compatibility also occurred in certain interspecific crosses.  相似文献   

2.
杨欣兰  潘瑛子  巴桑 《生态学报》2022,42(8):3216-3227
为揭示我国西藏高原湖泊原生动物群落结构特征及垂直分布格局,于2017年11月及2018年5月和9月,在巴松措中心分7层设置采样点,利用25号浮游生物网采集原生动物。采用活体观察和固定染色相结合的方法,共鉴定到原生动物195种(其中春季86种,夏季93种,秋季80种),隶属于2门11纲24目43科59属。其中以肉鞭门种类较丰富,砂壳类纤毛虫占优势。垂直分布的物种组成和群落结构复杂表现为:表层>中层>底层,物种多样性、丰富度和优势度指数表现为:表层>中层>底层,均匀度指数大多数为1;季节分布的物种组成和群落结构群复杂程度表现为:夏季>春季>秋季,物种多样性、丰富度指数表现为:夏季>秋季>春季,优势度指数表现为:夏季>秋季>春季,均匀度指数表现为:秋季>春季>夏季;优势物种和群落结构都会随水深的增加而减少。总体呈现出物种多样性较低、均匀度较高,具有明显的时空异质性。  相似文献   

3.
Weavers build domed, long-lasting nests that may also be adopted by other species for breeding, probably reducing the energetic costs of nest building to varying degrees. In an extensive literature search, 57 species were found to have at least one record of adopting a weaver nest. There is one known obligate nest user, the Pygmy Falcon Polihierax semitorquatus. Four species were classed as near obligate nest adopters. Four species were listed as common, 10 as occasional, and 38 species as rare nest adopters. Other than the falcon and lovebirds Agapornis species, these nest adopters are passerines. Of the 57 species of nest adopters, 35 species had confirmed eggs and/or chicks found in the weaver nests. Most nest adopter species were in the Estrildidae family (20 species), with three estrildids classed as near obligates. This was followed by the Muscicapidae family, species that build cup nests. By building their cup nests inside weaver nests, there is likely protection from adverse weather and predators. Overall, there appeared to be a large diversity of nest adopter species for the traditional savanna living weavers (Ploceus, Bubalornis, Anaplectes, Plocepasser and Philetairus).  相似文献   

4.
在室内查阅标本和查阅文献资料的基础上,结合野外实际调查,对秦岭地区紫堇属植物及其地理分布进行全面修订。结果表明:秦岭地区共有紫堇属植物28种,其中5种为秦岭特有种。地理分布格局研究表明:8种为秦岭广布种,7种为秦岭西部分布种,7种为秦岭中部分布种,1种为秦岭东部分布种,3种为秦岭中部和西部分布种,2种为中部和东部分布种。根据修订,给出了秦岭紫堇属植物分种检索表。  相似文献   

5.
Species traits which facilitate introduction and predominance have been quantitatively ranked using interval arithmetic to search for common patterns among 113 marine macroalgae introduced in Europe. Three main categories were used: dispersal, establishment and ecological impact. These were further subdivided into more specific categories, a total of 13. Introduced species were compared with the same number of native species randomized from the same families as the introduced. Invasive species (i.e. species having a negative ecological or economical impact) were also compared with non-invasive introductions, separately for the three algal groups. In many categories, as well as when adding all species, the introduced species ranked more hazardous than the native species and the invasive species ranked higher than the non-invasive ones. The ranking within the three main categories differed, reflecting different strategies between the species within the three algal groups. When all categories (excluding salinity and temperature) were summed, the top five risk species, all invasive, were, in descending order, Codium fragile spp.tomentosoides, Caulerpa taxifolia, Undaria pinnatifida, Asparagopsis armata and Grateloupia doryphora, while Sargassum muticum ranked eight and Caulerpa racemosa ten. Fifteen of the twenty-six species listed as invasive were among the twenty highest ranked.  相似文献   

6.
《农业工程》2019,39(4):306-320
The District Charsadda has a wide diversification with nature beauty and greenery. The area has rich biodiversity and natural resources. The District is geographically organized into two primary parts: Hashtnagar and Do Aaba. Research was carried out during 2017–18, in blooming season to collect different taxa from the area. The study depicted 253 taxa floristically with 189 genera and 71 families in which 4 families were pteridiophytes, 3 were gymnosperms and 64 were angiospermic families included 11 Monocot and 53 Dicot. The number of taxa per family varies from 1 to 56. Poaceae was the leading family in term of number of genera and species with 36 genera (19.04%) and 56 species (22.13%) followed by Asteraceae with 15 genera (7.936%) and 17 species (6.719%). The important groups in terms of species percentage were Dicots with a share of (53 species) followed by Monocots (11 species), Pteridophytes (5 species) and Gymnosperms (4 species). Herbaceous layer consists of 173 species (68.37%) followed by trees 46 species (18.18%), 25 species (9.881%) were shrub, 8 species (3.162%) were climbers and only 1 species (0.395%) was parasitic in the area. Biological spectrum depicted that Therophytes (126 species, 49.80%) and Microphyll (78 species, 30.83%) were the leading life form and leaf size classes. Ethnobotanical study proved that majority of species 164 were used as fodder/forage, 27 species were fruits, 28 species were vegetables, 28 species ornamental, 47 species fuel, 66 species were medicinals, 21 species used as timber, 8 species for thatching, 29 species for insect attractant and only 4 species used as spices (condiments) while some species have no local use in research area like Dryopteris stewartii, Equisetum arvense L., Marsilea L., Eichhornia crassipes (Mart.) Solms, and Potamogeton nodosus Poir. This is the first ever record of the area, no prior work exists in this regard. This work might help for future intensive and extensive researches.  相似文献   

7.
We addressed whether ridges, which are ecologically distinct from slopes, harbor specialized plant assemblages with a high representation of endemic species. We surveyed pteridophytes in 28 plots each of 400 m2 in ridge and slope forests at 2,430–2,660 m at three different localities in southeastern Ecuador. Data analysis was based on those 147 species with reliable determinations and excluded 14 undetermined species. Range sizes were expressed as the latitudinal distance between the northern- and southernmost collections, and species were then assigned to range-size quartiles, with the 1st quartile including the 25% most widespread species, etc. Differences in species richness per range-size quartile were determined using G-tests and differences in abundance using ANOVAs. The recorded 147 fern species were represented by 21,800 individuals, including 106 terrestrial (7,300 individuals) and 98 epiphytic species (14,500). Ridges had fewer species than slopes, and there was no higher representation of localized species on ridges. Overall, widespread species were weakly (R²?=?0.03) but significantly more abundant than localized species. Ridges had significantly higher abundances of terrestrial – but not of epiphytic – species compared to slopes, especially among the widespread species of the 1st range-size quartile. The contribution of ridge habitats to overall pteridophyte diversity and as habitats for endemics in our study region is low. Methodologically, the separation of species into range-size classes in an ecological study is novel and effective, as statistically significant patterns were found only for species belonging to the 1st or 4th quartiles.  相似文献   

8.
Capsule?Of 26 species of wintering waterbirds, 18 showed an increase in numbers, five showed a decrease and two showed no change.

Aim?To assess long-term trends in the numbers and distribution of the 26 most abundant wintering waterbird species in the Czech Republic.

Methods?We used International Waterbird Census data from between 48 and 639 wetland sites which had been counted annually in the Czech Republic from 1966 to 2008. From these data long-term changes in numbers and distributions were determined. Log-linear Poisson regression analysis was used to estimate missing data using trim software. The distribution of each species was described as the ratio of the number of sites occupied by that species to the total number of sites investigated.

Results?Increasing trends were found for 18 species, five species were found to be declining, one species was stable and two species were found with uncertain trends. Wintering distributions (the ratio of sites occupied by a given species to the total number of sites counted) increased in 16 species and decreased in two species, broadly correlated with the species changes in numbers.

Conclusion?In most species changes in numbers as well as changes in distribution followed the Western Palearctic population trends. Those species which increased were mainly piscivores and included geese, ducks and gulls. Scarcer species also exhibited an increase in numbers. The changes in numbers (both positive and negative) were more frequent among species associated with running water, whereas species which showed uncertain trends were more frequently recorded on standing water, which is more affected by variable weather conditions.  相似文献   

9.
An assessment of the DNA barcodes of Indian freshwater fishes   总被引:1,自引:0,他引:1  
Freshwater fishes in India are poorly known and plagued by many unresolved cryptic species complexes that masks some latent and endemic species. Limitations in traditional taxonomy have resulted in this crypticism. Hence, molecular approaches like DNA barcoding, are needed to diagnose these latent species. We have analyzed 1383 barcode sequences of 175 Indian freshwater fish species available in the databases, of which 172 sequences of 70 species were generated. The congeneric and conspecific genetic divergences were calculated using Kimura's 2 parameter distance model followed by the construction of a Neighbor Joining tree using the MEGA 5.1. DNA barcoding principle at its first hand approach, led to the straightforward identification of 82% of the studied species with 2.9% (S.E = 0.2) divergence between the nearest congeners. However, after validating some cases of synonymy and mislabeled sequences, 5% more species were found to be valid. Sequences submitted to the database under different names were found to represent single species. On the other hand, some sequences of the species like Barilius barna, Barilius bendelisis and Labeo bata were submitted to the database under a single name but were found to represent either some unexplored species or latent species. Overall, 87% of the available Indian freshwater fish barcodes were diagnosed as true species in parity with the existing checklist and can act as reference barcode for the particular taxa. For the remaining 13% (21 species) the correct species name was difficult to assign as they depicted some erroneous identification and cryptic species complex. Thus, these barcodes will need further assay and inclusion of barcodes of more specimens from same and sister species.  相似文献   

10.
魏滨  闫淑珍  陈双林 《广西植物》2016,36(2):137-144
为了揭示鼎湖山自然保护区黏菌的物种组成及物种多样性在不同生境的异同,该研究选择6个不同海拔高度的样地,从中收集地面基物和树皮基物进行湿室培养,通过物种鉴定和发生数量统计分析物种的组成和多样性。结果表明:共计获得6目8科18属49种黏菌,其中绒泡菌目(Physarales)最多(17种),其次为团毛菌目15种、发网菌目(Stemonitales)11种、无丝菌目(Lieeales)4种、鹅绒菌目(Ceratiomyxales)和刺轴菌目(Eehinosteliales)分别各1种。主要优势种为灰团网菌(Arcyria cinerea)(RA=27.03%)和垫形双皮菌(Diderma effusum)(RA=21.14%)。随着海拔的升高,黏菌物种多样性逐渐降低,Shannon-Wiener多样性指数最低值出现在海拔300 m处,为1.66±0.12;而其优势集中性指数最高,为0.25±0.05。两个样地的海拔高度相距越大,共有的物种数越少相似性指数越低。雨季共获得黏菌33种,旱季共获得黏菌40种,共有种为22种,相似性系数为60.27%,旱季基物上发生的黏菌Shannon-Wiener多样性指数显著高于雨季。地面基物上的黏菌物种数为39种,高于树皮基物的26种,且两者的Shannon-Wiener多样性指数具有显著性差异,表明黏菌对地面基物的偏好性大于树皮基物。  相似文献   

11.
The fungal genus Ulocladium consists mostly of saprotrophic species and can readily be isolated from dead vegetation, rotten wood, paper, textiles and other cellulose containing materials. Thus, they must produce cellulolytic and hemicellulolytic enzymes. In this study fifty Ulocladium strains from ten different species were tested for enzyme activities on 14 different azurine-cross-linked (AZCL) substrates and analyzed by multivariate analysis. The tested strains of Ulocladium were found to produce a broad enzyme profile. Most species in Ulocladium were able to produced high amounts of enzymes that degraded amylose, arabinoxylan, β-glucan, cellulose and xylan; however, variations between species as well as between individual strains in each species were seen. Overall, the enzyme profiles were found to be species specific, but also source of isolation impacted the enzymes produced. The results suggest that species identity as well as isolation source must be considered when screening microorganisms for enzymes.  相似文献   

12.
山东聊城雀形目鸟类及其生态分布   总被引:3,自引:1,他引:2  
报道了山东省聊城境内雀形目鸟类的分布 ,共记录到 1 4科 5 9种。其中留鸟 1 3种 ;其它繁殖鸟 1 5种 ;冬候鸟 9种 ;旅鸟 2 2种。近 1 0年来调查资料显示 ,该区鸟类的物种数及多数种类的数量在不同季节和不同年份呈不稳定分布 :约 60 %的鸟类的数量趋于减少 ;少数种类基本稳定 (三道眉草等 )或呈增长趋势 (灰喜鹊等 )。 [蒙古 ]百灵、文须雀为山东省分布新纪录  相似文献   

13.
Three species of Rhytismatales on Berberis were found from Sichuan and Yunnan provinces in China. Two of them were described as new species to science, namely Hypoderma minteri and Lophodermium johnstonii. The third one was a known species, Hypoderma berberidis. The phylogenetic relationships of these species within the Rhytismatales were analyzed based on internal transcriber spacer ribosomal DNA. The results showed that the species of the Rhytismatales on Berberis, unlike most species on pines, were not closely related. Three ITS sequences from GenBank, named there as Lirula macrospora, were used in this study, but were found to be from misidentified sources. A key to species of Rhytismatales on Berberis worldwide is also given.  相似文献   

14.
《Ostrich》2013,84(3):259-264
Mixed-species foraging flocks were studied at Kichwa Tembo Camp on the edge of the Masai Mara National Reserve in Kenya between July and September 2004. Observations were made on 29 mixed-species flocks, in which 24 species participated. African Paradise-Flycatcher Terpsiphone viridis, Black-backed Puffback Dryoscopus cubla, Grey-backed Camaroptera Camaroptera brachyura, Collared Sunbird Hedydipna collars and Cabanis's Greenbul Phyllastrephus cabanisi were the most common participants in mixed-species flocks, as well as among the most frequently encountered bird species overall. The Black-backed Puffback was identified as the nuclear species in flocks due to their abundance and frequency with which they were followed by other species. Mixed-species flocks represent another niche dimension in this diverse bird community, but few of these species could be described as flock specialists; most of the birds observed in mixed-species flocks in this study were opportunistic attendant species, including the African Pygmy-Kingfisher Ispidina picta, not previously described as joining mixed-species flocks.  相似文献   

15.
Capsule Expert‐based classification of bird species as habitat specialists and as generalists agrees with objective measures of species’ habitat requirements based on large‐scale monitoring data.

Aims To compare habitat specialization of 137 common bird species breeding in the Czech Republic using three different measures and to test their relationships to species’ abundance and habitat associations.

Methods Data on bird abundance and surveyed habitats were collected through a standardized monitoring scheme of common breeding species in the Czech Republic. From these data we calculated a quantitative species specialization index (SSI). Canonical correspondence analysis (CCA) was applied to calculate species’ habitat niche breadth and the level of association of each species to the main habitats. A panel of 11 local bird experts classified each species as habitat generalist or habitat specialist.

Results Species classified as habitat specialists by expert opinion showed higher habitat specialization according to the SSI, as well as according to CCA‐based habitat niche breadth. These species were also more closely associated with one of the main habitat types. These relationships were significant even after controlling for abundance.

Conclusions As expert opinion accords with the level of species’ habitat specialization expressed using two quantitative objective measures, we suggest that these characteristics reflect real interspecific variation in the breadth of habitat requirements in birds. Interspecific differences in habitat specialization are not caused solely by the variability in abundance among species.  相似文献   

16.
In this study, 121 wild edible plants used as food in Anatolia were surveyed to determine the plant parts used and their detailed preparation methods. The results of this study show that the plants may be boiled, fried in fat, and eaten raw or as rolled vegetables. They may also be consumed as pickles, fruits, sweets and spices, and drunk as cold and hot drinks. Thirty species (8 genera) were identified as belonging to the Lamiaceae family, 15 species (15 genera) belong to the Asteraceae family, 13 species (5 genera) belong to the Rosaceae family, 8 species (7 genera) belong to the Brassicaceae family, 6 species (3 genera) belong to the Orchidaceae family and 5 species (5 genera) belong to the Apiaceae family. The genera represented by the highest number of species in the study are as follows:Sideritis L. is represented by 13 species, Origanum L. by 7 species,Rubus L. by 5 species,Thymus L. by 4 species andRumex L. by 4 species.  相似文献   

17.
Erwin’s method for estimating total global species richness assumes some host‐specificity among the canopy arthropods. This study examined possible host habitat specialization in two major groups of soil arthropods, the oribatid and mesostigmatid mites, by sampling beneath three tree species: Eucalyptus pilularis Smith, Eucalyptus propinqua Deane and Maiden and Allocasuarina torulosa (Aiton) L. Johnson. The sample sites were in the Lansdowne State Forest, New South Wales, Australia and the three tree species were selected on the basis of their known differential effects on soil. Sampling was conducted over three seasons, and 79 oribatid and 34 mesostigmatid species were identified from 25 196 and 3634 individuals, respectively. Tree species had little effect on mite species composition with only three oribatid species and no mesostigmatid species identified as host‐habitat specialists using a niche breadth measure. Of mite species found under E. pilularis, E. propinqua and A. torulosa trees, 2%, 1% and 0% were defined as host‐habitat specialists, respectively. In contrast, tree species had significant and consistent effects on mite community structure, which differed in relative abundance of the oribatid species, their size class distributions and species rankings. In the mesostigmatid communities, there was a difference in the ranking of the mite species among tree species. Although it was demonstrated that tree species have an impact on the soil environment, the differences between tree species were insufficient to change species composition. The low degree of host‐habitat specialization suggested that other factors were more important for determining mite species composition at a site, and soil mite host‐habitat specialization may not make a large contribution to estimates of total global species richness using methods such as those proposed by Erwin (1982) .  相似文献   

18.
Invasion by alien organisms is a common worldwide phenomenon, and many alien species invade native communities. Invasion by alien species is especially likely to occur on oceanic islands. To determine how alien species become integrated into island plant–insect associations, we analyzed the structure of tree–beetle associations using host plant records for larval feeding by wood-feeding beetles (Coleoptera: Cerambycidae) on the oceanic Ogasawara Islands in the northwestern Pacific Ocean. The host plant records comprised 109 associations among 28 tree (including 8 alien) and 26 cerambycid (including 5 alien) species. Of these associations, 41.3% involved at least one alien species. Most native cerambycid species feed on host trees that have recently died. Alien trees were used by as many native cerambycid species (but by significantly more alien cerambycid species) as were native trees. Native cerambycid species used as many alien tree species (but significantly more native tree species) as did alien cerambycids. Thus, we observed many types of interactions among native and alien species. A network analysis revealed a significant nested structure in tree–cerambycid associations regardless of whether alien species were excluded from the analysis. The original nested associations on the Ogasawara Islands may thus have accepted alien species.  相似文献   

19.
Grun , Paul . (Pennsylvania State U., University Park.) Early stages in the formation of internal barriers to gene exchange between diploid species of Solanum. Amer. Jour. Bot. 48(1): 79–89. Illus. 1961.—Internal barriers restricting development of F1 hybrids in crosses among closely related diploid species of Solanum belonging to the series Tuberosa and Commersoniana were studied to determine the early stages in development of barriers to gene exchange. Both of the parental series (species complexes) are native to South America, the Tuberosa occurring along the length of the Andes, while the Commersonia occur at lower altitudes in Argentina, Paraguay, and Bolivia. They are distinguished by a fair number of morphological characters. Following crossings between the species of each series and between species of the different series comparisons were made of the number of berries formed per attempted cross, seed per berry, percentage seed germination, and F1 vigor and pollen fertility. Although the species used were closely enough related that all could readily be hybridized, berry and seed set following crosses between species of different series were on the average lower than they were following crosses between species of the same series. These barriers are just forming and are expressed in a varying manner, so that there were significant differences between species of the same series, and even between clones of the same species in barrier expression. The barriers of some of the species were expressed only when they were tested as female or as male parent. The inter-series F1 seeds germinated as well as did those of the parent species and the hybrids had a normal vigor and pollen fertility.  相似文献   

20.
We examined palatability of 37 species of nonencrusting macroalgae from the Antarctic Peninsula. This represents approximately 30% of the entire antarctic macroalgal flora and 75% of the 49 nonencrusting species we collected. Organic extracts from most species were also prepared and mixed into artificial foods. We examined palatability using feeding bioassays with three common, macroalga‐consuming animals (an omnivorous antarctic rockfish, Notothenia coriiceps; an omnivorous sea star, Odontaster validus; and a herbivorous amphipod, Gondogenia antarctica). Thallus pieces from 23 of 34 macroalgal species tested with the fish (68%) were rejected. Of the 23 species rejected as thallus, organic extracts of 16 were bioassayed using the fish with 9 (56%) unpalatable. Thallus pieces from 21 of 36 macroalgal species tested with the sea star (58%) were rejected. Of the 21 species rejected as thallus, organic extracts of 20 were bioassayed using the sea stars and 14 (70%) were unpalatable. Overall, 28 of the 37 species assayed as thallus (76%) were rejected by either or both the fish and sea stars. The amphipod assay was not suitable for use with thallus but was utilized with organic extracts of 23 macroalgal species that were rejected as thallus by either or both the fish and sea stars. Of these, 14 (61%) of the species' extracts were rejected by the amphipods. Unpalatability was highest among the brown algae examined with only an ephemeral, ectocarpoid species not rejected as thallus out of 10 species tested. Of the remaining nine brown algal species, six of seven tested were also unpalatable as extracts, including all the ecologically dominant, perennial species in the area. We conclude that unpalatability to herbivores is common in antarctic macroalgae and that chemical defenses may play an important role in the unpalatability of many algal species (NSF OPP9814538, OPP9901076).  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