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1.
Many fungi behave as endophytes in grasses. Unlike the well known Epichloë/Neotyphodium species, most other endophytes are not capable of systemic colonization of plant organs, or seed transmission. The species diversity of the non-systemic endophytic mycobiota of grasses is large, dominated by ascomycetes. The relative abundance of species is very unequal, a few dominant taxa like Acremonium, Alternaria, Cladosporium, Epicoccum and Penicillium spp., occur in many grasses and locations. In contrast, many rare species are isolated only once in endophyte surveys. The possible ecological functions of endophytes are diverse, and often unknown. Latent pathogens represent a small fraction of endophytic mycobiotas, indicating that many non-pathogenic fungal taxa are able to enter plants overriding defence reactions. Some dominant species behave as latent saprotrophs, sporulating when the host tissue dies. Endofungal viruses and bacteria occur among endophytic species, but their effect in their hosts is largely unknown.  相似文献   

2.
Climate change in Africa poses a serious threat to many ecosystems and livelihoods, making them vulnerable to climate-related risks. Gum and resin bearing tree species as the genus Boswellia are the main economic and livelihood sources in most dryland areas of Africa. We use species distribution models to find critical sites where Boswellia species may no longer occur in the future. Our models identify potential regions that could benefit from their cultivation and promote conservation efforts for the species to thrive. We projected models to new CMIP6 scenarios and different dispersal profiles. Despite the prevailing aridity already imposed on the species, Boswellia distribution shows a dramatic reduction. Future investments in Boswellia restoration and strategies to promote sustainable extraction of resources may be key to sustain populations and Boswellia dominated forests in many parts of the African continent.  相似文献   

3.
The genus Cordia (Boraginaceae) is made up of a great many species widely distributed in tropical and subtropical regions of the world. The leaves ofCordia myxa, as also those of many other species of the same genus, have been utilized in the traditional medicine of many countries for the treatment of a variety of diseases. Observed by light microscope and by scanning electron microscope the histological characteristics of the leaf ofCordia francisci, C. martinicensis, C. serratifolia andC. ulmifolia, species grown in Sicily, compared also with those of the leaves ofC. myxa originating from Africa, are described in detail. It has been possible to reveal some morphological elements that allow leaf identification and the differentiation of the drugs examined.  相似文献   

4.
Birds and figs are conspicuous members of the tropical and subtropical ecosystems. Because they are easily observed and very speciose, their relationships have been well studied in many areas, and the figs are considered a keystone resource for many bird species which are efficient fig seed dispersers. Taiwan has a relatively high endemism rate for many taxa (17% of bird species) but because of its high human population density, most lowland habitats are heavily developed, of which much of it covered by dense urban habitation. To establish the importance of urban figs for birds, we focused our surveys mostly on three common urban fig species (Ficus caulocarpa, F. microcarpa and F. subpisocarpa). We observed trees with ripening figs from July 2013 to December 2016 in order to determine the composition of the fig-consuming bird community. In addition, we added all the information available in the scientific literature and birdwatchers' observations which we could find. In total, we observed 42 bird species consuming 18 fig species. The bird diversity in urban areas was non-negligible even during winter. Therefore, there are two reasons why figs are important for Taiwan's bird avifauna: in cities, the tree diversity is generally low so that figs provide a stable food resource; and since figs are fruiting all year-round, they are one of the few reliable resources available during winter when many migrant birds overwinter in Taiwan. Already crucial for many species in tropical and subtropical forests, fig trees may also be essential for urban birds in tropical and subtropical regions.  相似文献   

5.
Accurate delimitation of species is a critical first step in protecting biodiversity. Detection of distinct species is especially important for groups of organisms that inhabit sensitive environments subject to recent degradation, such as creeks, springs, and rivers in arid or semi-desert regions. The genus Dionda currently includes six recognized and described species of minnows that live in clear springs and spring-fed creeks of Texas, New Mexico (USA), and northern Mexico, but the boundaries, delimitation, and characterization of species in this genus have not been examined rigorously. The habitats of some of the species in this genus are rapidly deteriorating, and many local populations of Dionda have been extirpated. Considering the increasing concerns over degradation of their habitat, and pending a more detailed morphological revision of the genus, we undertook a molecular survey based on four DNA regions to examine variation over the range of the genus, test species boundaries, and infer phylogenetic relationships within Dionda. Based on analyses of two mitochondrial (cytb and D-loop) and two nuclear (Rag1 and S7) DNA regions from specimens collected throughout the range of Dionda, we identified 12 distinct species in the genus. Formerly synonymized names are available for two of these species, and four other species remain undescribed. We also redefine the known range of six species. The limited distribution of several of the species, coupled with widespread habitat degradation, suggests that many of the species in this genus should be targets for conservation and recovery efforts.  相似文献   

6.
Biological invasions represent a serious threat for the conservation of biodiversity in many ecosystems. While many social insect species and in particular ant species have been introduced outside their native ranges, few species have been successful at invading temperate forests. In this study, we document for the first time the relationship between the abundance of the introduced ant, Pachycondyla chinensis, in mature forests of North Carolina and the composition, abundance and diversity of native ant species using both a matched pair approach and generalized linear models. Where present, P. chinensis was more abundant than all native species combined. The diversity and abundance of native ants in general and many individual species were negatively associated with the presence and abundance of P. chinensis. These patterns held regardless of our statistical approach and across spatial scales. Interestingly, while the majority of ant species was strongly and negatively correlated with the abundance and presence of P. chinensis, a small subset of ant species larger than P. chinensis was either as abundant or even more abundant in invaded than in uninvaded sites. The large geographic range of this ant species combined with its apparent impact on native species make it likely to have cascading consequences on eastern forests in years to come, effects mediated by the specifics of its life history which is very different from those of other invasive ants. The apparent ecological impacts of P. chinensis are in addition to public health concerns associated with this species due to its sometimes, deadly sting.  相似文献   

7.
海链藻(Thalassiosira)与圆筛藻(Coscinodiscus)的形态学比较研究   总被引:1,自引:0,他引:1  
李扬 《植物研究》2009,29(3):282-288
海链藻属(Thalassiosira)和圆筛藻属(Coscinodiscus)的种类繁多,是硅藻门中的大属和代表属。两者的形态学特征具有较多相似之处,易混淆鉴定。通过光学显微镜和电镜观察,比较研究了海链藻和圆筛藻种类的形态学特征。海链藻种类除了具有1~2个唇形突之外,还具有数量较多的支持突,少数种类具有闭合突;筛膜位于壳面内侧;中孔在壳面外侧。而圆筛藻种类只具有数量众多的唇形突,且其中两个较大;筛膜位于壳面外侧;中孔在壳面内侧。由于两属形态学特征的区别只有在电镜下才能清晰观察到,因此尚有较多的分类修订工作需要进行。  相似文献   

8.
Phrynosomatid lizards are among the most common and diverse groups of reptiles in western North America, Mexico, and Central America. Phrynosomatidae includes 136 species in 10 genera. Phrynosomatids are used as model systems in many research programs in evolution and ecology, and much of this research has been undertaken in a comparative phylogenetic framework. However, relationships among many phrynosomatid genera are poorly supported and in conflict between recent studies. Further, previous studies based on mitochondrial DNA sequences suggested that the most species-rich genus (Sceloporus) is possibly paraphyletic with respect to as many as four other genera (Petrosaurus, Sator, Urosaurus, and Uta). Here, we collect new sequence data from five nuclear genes and combine them with published data from one additional nuclear gene and five mitochondrial gene regions. We compare trees from nuclear and mitochondrial data from 37 phrynosomatid taxa, including a “species tree” (from BEST) for the nuclear data. We also present a phylogeny for 122 phrynosomatid species based on maximum likelihood analysis of the combined data, which provides a strongly-supported hypothesis for relationships among most phrynosomatid genera and includes most phrynosomatid species. Our results strongly support the monophyly of Sceloporus (including Sator) and many of the relationships within it. We present a new classification for phrynosomatid lizards and the genus Sceloporus, and offer a new tree with branch lengths for use in comparative studies.  相似文献   

9.
Biogeography of polypores distributed in the Malesian region is reviewed. Some of the species reported from this region are pantropical or paleotropical and widely distributed along the equator. Several species are restricted to lowland areas of Malesia and adjacent regions, and can be classified as Asian or Asian-Oceanian tropical species. Some species have only been recorded from lowland areas of Malesia at present, but detailed distributions are unclear for many of them. Some lowland Malesian species are also distributed in temperate areas of East Asia; among them, few species are circumglobal in the Northern Hemisphere, whereas many others are tropical species showing continuous distributions up to the warm temperate areas of East Asia. Species recorded from highland areas of Malesia include tropical species common to lowland Malesia, temperate species common to temperate Asia, and endemic species in highland areas of Malesia and adjacent regions. Regarding the factors that delimitate distribution of the Malesian polypores, I discuss polypore host preference, response to physical environmental factors, and dispersal ability. Systematics and ecological characteristics are briefly discussed for selected Malesian polypores: Corneroporus subcitrinus, Paratrichaptum accuratum, Postia stellifera and Roseofavolus eos.  相似文献   

10.
The electrophoretic mobilities of the cytoplasmic ribosomal proteins of several species of plants were compared using two-dimensional electrophoresis. The total number of proteins as well as the number of acidic and basic proteins in individual species varied markedly. Of the species examined, Triticum aestivum had the highest number of basic cytoplasmic ribosomal proteins and Hordeum vulgare had less than half as many. However, marked similarities were noted in the electrophoretic mobilities of many of the proteins, especially for wheat, rye, and barley and for peas and beans. There was a statistically significant positive correlation between the numbers of basic proteins in the species and their chromosome number.  相似文献   

11.
The reproductive systems of fourCardamine species were compared.C. flexuosa ssp.flexuosa, a self-pollinated winter annual in fallow paddy fields, produces numerous small seeds.C. flexuosa ssp.fallax, a self-pollinated year-long annual in gardens and roadsides, also produces many small seeds.C. impatiens, a self-pollinated annual in forest margins, similarly produces numerous small seeds.C. scutata is a self-pollinated perennial in ill-drained paddy fields and creeks; its vegetative reproduction is not predominant, and it produces relatively many seeds.C. lyrata, a cross-pollinated perennial with self-incompatibility in ill-drained paddy fields and creeks, produces fewer and heavier seeds, but it does produce many ramets. Moreover, in seed-dispersal mechanisms and germination behavior of fourCardamine species several adaptive characteristics to their habitats are found. These observations on the reproductive systems of fourCardamine species apparently present different characteristics of life-history strategy for each of them.  相似文献   

12.
13.
Factors shaping the distribution and abundance of species include life‐history traits, population structure, and stochastic colonization–extinction dynamics. Field studies of model species groups help reveal the roles of these factors. Species of Caenorhabditis nematodes are highly divergent at the sequence level but exhibit highly conserved morphology, and many of these species live in sympatry on microbe‐rich patches of rotten material. Here, we use field experiments and large‐scale opportunistic collections to investigate species composition, abundance, and colonization efficiency of Caenorhabditis species in two of the world''s best‐studied lowland tropical field sites: Barro Colorado Island in Panamá and La Selva in Sarapiquí, Costa Rica. We observed seven species of Caenorhabditis, four of them known only from these collections. We formally describe two species and place them within the Caenorhabditis phylogeny. While these localities contain species from many parts of the phylogeny, both localities were dominated by globally distributed androdiecious species. We found that Caenorhabditis individuals were able to colonize baits accessible only through phoresy and preferentially colonized baits that were in direct contact with the ground. We estimate the number of colonization events per patch to be low.  相似文献   

14.
Approximately 70 species of Bactrocera fruit flies (Diptera: Tephritidae) are polyphagous economic pests that attack many important agricultural crops. Several of these Bactrocera species are also highly invasive, and many countries operate continuous, large-scale trapping programs to detect incipient infestations. Detection programs rely heavily on traps baited with male lures, with males of some species responding to raspberry ketone (RK; or its synthetic analogue cue-lure [CL]) and males of other species responding to methyl eugenol (ME). These lures (plus naled, an insecticide) are currently applied as liquids, although this procedure is time-consuming and may expose workers to health risks. Recent field tests, conducted largely in Hawaii, have shown that traps baited with a solid formulation (termed a wafer) that contains both RK and ME (plus dichlorvos, an insecticide) capture as many or more B. dorsalis (Hendel) and B. cucurbitae (Coquillett) males as traps baited with the standard liquid lures. While these results are promising, a more complete evaluation of the solid formulation requires testing in a region with a diverse assemblage of Bactrocera species, since interspecific variation in male response to lures has been reported. The objective of the present investigation was to assess the relative effectiveness of liquid versus solid formulations of male lures in Malaysia, a country known to harbor a large assemblage of Bactrocera species. Based on a 12-week sampling period, we found that, contrary to the Hawaiian results, traps baited with the wafer captured significantly fewer males than traps baited with liquid lures for all five ME-responding taxa analyzed and for one of the three RK/CL-responding species analyzed. Possible explanations for the discrepancy between these and earlier findings are offered.  相似文献   

15.
The widespread cyanolichen genus Peltigera comprises many insufficiently known poorly delimited and/or undescribed species. Phylogenetic analysis of 252 Peltigera specimens from a wide range of habitat types in Estonia revealed 31 putative taxa (OTUs). Multivariate analysis revealed habitat-specific segregation between the Peltigera species along a gradient from humid eutrophic forests to dry oligotrophic forests and grasslands and along a soil pH gradient from alkaline soils of alvar grasslands to acidic soils of conifer forests. The diversity of Peltigera was the highest on roadsides and dunes and the lowest in alvar habitats which, however, supported the unique assemblage of undescribed Peltigera taxa. Deciduous broad-leaved forests, too, included several undescribed or rare and red-listed species. The results demonstrate that in Estonia many Peltigera species have narrow habitat requirements and are at present threatened by habitat loss and degradation.  相似文献   

16.
By analyzing the genomic sequences of 12 Bacteroidales species, we found that all intestinal species have numerous polysaccharide biosynthesis loci, many with promoters that we demonstrate undergo DNA inversion. This feature is not conserved in the Bacteroidales order as a whole, as oral species do not share these genetic features.  相似文献   

17.
Competition among males for mates may partially explain the predominant dispersal of juvenile male California ground squirrels (Spermophilus beecheyi). I tested the generality of this hypothesis by comparing dispersal patterns in many species of mammals. In most polygynous and promiscuous species of mammals, juvenile males are the predominant dispersers. In most monogamous species of mammals, juvenile males and juvenile females are predominant dispersers with little distinction as to sex. While many factors may influence dispersal, achieving outcrossing and advantages in competition for mates are most likely to explain predominant dispersal by juvenile males in many mammal species.  相似文献   

18.
Human landscape modification has led to habitat fragmentation for many species. Habitat fragmentation, leading to isolation, decrease in patch size and increased edge effect, is observed in fen ecosystems that comprise many endangered plant species. However, until now it has remained unclear whether habitat fragmentation per se has a significant additional negative effect on plant species persistence, besides habitat loss and degradation. We investigated the relative effect of isolation, habitat size, and habitat edge compared to the effect of habitat degradation by including both ‘fragmentation variables’ and abiotic variables in best subsets logistic regression analyses for six fen-plant species. For all but one species, besides abiotic variables one or more variables related to fragmentation were included in the regression model. For Carex lasiocarpa, isolation was the most important factor limiting species distribution, while for Juncus subnodulosus and Menyanthes trifoliata, isolation was the second most important factor. The effect of habitat size differed among species and an increasing edge had a negative effect on the occurrence of Carex lasiocarpa and Pedicularis palustris. Our results clearly show that even if abiotic conditions are suitable for certain species, isolation of habitat patches and an increased habitat edge caused by habitat fragmentation affect negatively the viability of characteristic fen plant species. Therefore, it is important not only to improve habitat quality but also to consider spatial characteristics of the habitat of target species when deciding on plant conservation strategies in intensively used landscapes, such as fen areas in Western Europe and North America.  相似文献   

19.
The genus Sida L. (family: Malvaceae) is widely used in India and many other countries including China, South East Asia, Africa and South America for treating various neurological disorders and for improving general health and vigour. However, as with many other herbal medicines, it is believed that the Sida products sold in the market may be adulterated with other related or unrelated plant species. In this study, we investigate species adulteration in the raw herbal trade of Sida natural health products (NHPs) in southern India. DNA barcoding was used as a tool to identify the ingredients in the NHPs. A biological reference material (BRM) library for Sida and closely related species was developed using taxonomically authenticated species. DNA barcodes for the species were developed using one nuclear (ITS) and two chloroplast regions (matK and psbA-trnH). The psbA-trnH and ITS region were found to effectively discriminate all species with an interspecific distance of 0.133 and 0.149 and intra-species distance of 0.007 and 0.015 respectively. These DNA barcodes were used to identify the ingredients in raw Sida herbal products obtained from 10 markets in Southern India. Our study indicated that species adulteration in the market samples is rampant especially in case of Sida cordifolia, where all the market samples analyzed were Sida acuta. We discuss the results and the need for a robust herbal drug authentication system to regulate the quality in raw herbal trade market.  相似文献   

20.
Leaves from herbarium specimens of 505 species and varieties of North AmericanAstragalus were examined for the presence of organic nitro-toxins. The relative concentration of these nitro compounds was determined for the 263 nitro-containing species and varieties. Chemotaxonomic relationships existed among many species so that the presence, molecular configuration, and concentration of the nitro-toxins in the species examined could be used to predict the occurrence of these toxins in other taxa. Geographic differences were also noted for varieties of one species,A. robbinsii (Oakes) A. Gray.  相似文献   

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