车前属(Plantago L.)植物生态与进化生物学研究进展

车前属植物是理论生态学、生理生态学、进化生物学研究的理想材料。本文综述了近年来国内外学者在车前属生态学、进化生物学、系统分类学方面的研究概况。     

Deep-sea pelagic ichthyonekton diversity in the Atlantic Ocean and the adjacent sector of the Southern Ocean

Aim Deep‐sea pelagic diversity is poorly understood. Local (SL) and regional (SR) ichthyonekton species richness are presented and analysed with respect to local and regional environmental factors, and biogeographical processes. Location Sixty‐six stations from the Atlantic Ocean and adjacent sector of the Southern Ocean, 65° N to 57° S. Methods Estimation of SL by means of rarefaction. Stepwise evaluation of SL and SR relationships by means of the second‐order corrected Akaike information criterion (AICc) after locally weighted scatterplot smoothing (LOESS) and linear fitting, analysis of saturation effects by means of slopes of species accumulation curves (log–log plots). Results Latitudinal gradients were present for SL and SR, and were asymmetric between the Northern and Southern hemispheres. Relatively low species richness was encountered for the Southern Ocean. Asymmetry at the regional level by means of higher SR was attributed to area effects in the South Atlantic. Log–log plots indicated saturation of local assemblages and dependence on environmental factors. SL was related to productivity; this relationship was hump‐shaped. SR was positively related to area size and negatively to seasonality of production. Biogeographical effects were indicated in that SR peaks coincided with overlap zones of boreal and tropical faunas as a consequence of historical faunal exchange processes. Main conclusions The stepwise approach allowed for distinction between effects of area size, productivity and biogeographical processes on diversity at local and regional scales. Productivity in particular is important in two ways. At the local scale, the link of productivity to SL is explained by a successional‐functional hypothesis of resource utilization, whereas the seasonality effect for SR reinforces the hypothesis of dependence of deep‐sea fishes on seasonality of production through changes of life‐history traits. The causes of low Antarctic faunal diversity remained unresolved.     

Genetic panmixia and demographic dependence across the North Atlantic in the deep-sea fish,blue hake (Antimora rostrata)

The efficient investment of resources and effort into conservation strategies depends on the accurate identification of management units. At the same time, understanding the processes by which population structure evolves requires an understanding of the conditions under which panmixia may exist. Here, we study a species with an unusual, apparently sex-biased pattern of distribution, and test the hypothesis that distribution processes associated with this pattern (for example, congregating at a single dominant spawning site or periodic mixing during reproduction) could lead to panmixia over a large geographic range. Using 13 microsatellite markers, we compared 393 blue hake (Antimora rostrata) from 11 sample sites across a geographic range of over 3000 km, and found no evidence of population structure. We estimated current effective population size and found it to be large (∼15 000) across the sampled area. In addition, we used simulation models to test expectations about demographic correlation among populations and our ability to detect relevant levels of gene flow. All data were consistent with the interpretation of long-range panmixia.     

Abundant proteorhodopsin genes in the North Atlantic Ocean

Proteorhodopsin (PR) is a light-driven proton pump that has been found in a variety of marine bacteria, including Pelagibacter ubique , a member of the ubiquitous SAR11 clade. The goals of this study were to explore the diversity of PR genes and to estimate their abundance in the North Atlantic Ocean using quantitative polymerase chain reaction (QPCR). We found that PR genes in the western portion of the Sargasso Sea could be grouped into 27 clusters, but five clades had the most sequences. Sets of specific QPCR primers were designed to examine the abundance of PR genes in the following four of the five clades: SAR11 ( P. ubique and other SAR11 Alphaproteobacteria ), BACRED17H8 ( Alphaproteobacteria ), HOT2C01 ( Alphaproteobacteria ) and an uncultured subgroup of the Flavobacteria . Two groups (SAR11 and HOT2C01) dominated PR gene abundance in oligotrophic waters, but were significantly less abundant in nutrient- and chlorophyll-rich waters. The other two groups (BACRED17H8 and Flavobacteria subgroup NASB) were less abundant in all waters. Together, these four PR gene types were found in 50% of all bacteria in the Sargasso Sea. We found a significant negative correlation between total PR gene abundance and nutrients and chlorophyll but no significant correlation with light intensity for three of the four PR types in the depth profiles north of the Sargasso Sea. Our data suggest that PR is common in the North Atlantic Ocean, especially in SAR11 bacteria and another marine alphaproteobacterial group (HOT2C01), and that these PR-bearing bacteria are most abundant in oligotrophic waters.     

Modelled spatial distribution of marine fish and projected modifications in the North Atlantic Ocean

The objectives of this work were to examine the past, current and potential influence of global climate change on the spatial distribution of some commercially exploited fish and to evaluate a recently proposed new ecological niche model (ENM) called nonparametric probabilistic ecological niche model (NPPEN). This new technique is based on a modified version of the test called Multiple Response Permutation Procedure (MRPP) using the generalized Mahalanobis distance. The technique was applied in the extratropical regions of the North Atlantic Ocean on eight commercially exploited fish species using three environmental parameters (sea surface temperature, bathymetry and sea surface salinity). The numerical procedure and the model allowed a better characterization of the niche (sensu Hutchinson) and an improved modelling of the spatial distribution of the species. Furthermore, the technique appeared to be robust to incomplete or bimodal training sets. Despite some potential limitations related to the choice of the climatic scenarios (A2 and B2), the type of physical model (ECHAM 4) and the absence of consideration of biotic interactions, modelled changes in species distribution explained some current observed shifts in dominance that occurred in the North Atlantic sector, and particularly in the North Sea. Although projected changes suggest a poleward movement of species, our results indicate that some species may not be able to track their climatic envelope and that climate change may have a prominent influence on fish distribution during this century. The phenomenon is likely to trigger locally major changes in the dominance of species with likely implications for socio‐economical systems. In this way, ENMs might provide a new management tool against which changes in the resource might be better anticipated.     

The Distribution and Ecology of Ariosoma Balearicum (Congridae) Leptocephali in the Western North Atlantic

A total of 4589 leptocephali of the congrid eel, Ariosoma balearicum, were examined from 17 cruises in the western North Atlantic Ocean. Myomere counts made on 915 of these indicated there were two ranges of number of myomeres that appear to be associated with separate spawning populations. Those with the higher range (high count: 128–137) were consistently 70–100mm in length in the Sargasso Sea from February to April and 20–80mm in length in the northern Sargasso Sea and Gulf Stream from September to October. Those with the lower range (low count: 120–130) were rare in the northern and eastern Sargasso Sea where they had consistently greater lengths than high count leptocephali and were most abundant in the Florida Current and Providence Channel. The geographic distributions of size and myomere ranges in relation to hydrography provide strong support for the hypothesis that high count eels found along the South Atlantic Bight (SAB) migrate across the Florida Current to spawn in the northwest Sargasso Sea. This migratory pattern is similar to those of Anguilla rostrata and Conger oceanicus, which use the southern Sargasso Sea for development as larvae. However, the distribution of high count leptocephali suggests that they use the entire Sargasso Sea gyre as a development area as larvae before crossing the Florida Current and recruiting to the SAB. The low count eels inhabiting the Bahamas appear to spawn near the banks and their abundance in the Providence Channel and southwest Sargasso Sea suggests most are retained close to the Bahamas. These two distinct styles of spawning, distribution and recruitment of larvae are hypothesized to be related to the different hydrographic regimes of the two juvenile habitats and the resulting constraints on growth and recruitment of larvae. Vertebral and myomere counts reported from other areas suggest there are distinct populations in other regions of the North Atlantic Ocean.     

Biology of the Sand Smelt, Atherina presbyter (Teleostei: Atherinidae), Off the Canary Islands (central-east Atlantic)

Atherina presbyter is a common fish off the Canary Islands. Age, growth, reproduction, and mortality of the species are studied based on sampling carried out from July 1995 to June 1996. The parameters of the total length–total weight relationship are: a=0.004521, and b=3.0771. Otoliths age readings indicate that the sampled population consists of four age groups (0–III years). The von Bertalanffy growth parameters for all individuals are: L=122mm total length, k=0.79year^–1, and t₀=–0.21 years. Individuals grow quickly in their immature first year, attaining approximately 60% of their maximum length. After the first year, the annual growth rate drops rapidly, because the energy is probably diverted to reproduction. It is a gonochoristic species with no evidence of sexual dimorphism. The gonad is present as a single diffuse testis in males and as a single discrete ovary in females. The overall ratio of males to females is not significantly different from 1:1. The reproductive period of the species is protacted (February to June). The peak of the reproductive effort occurs in April–May. The size at first maturity is 68mm. The population is being heavily exploited.     

New plagioporines (Digenea: Opecoelidae) from deep-sea fishes of the North Atlantic Ocean

Three new species of digenean are described from demersal fishes taken in deep waters of the northwestern and northeastern Atlantic Ocean: Podocotyle schistotesticulata n. sp. from Antimora rostrata; P. harrisae n. sp. from Coryphaenoides (Lionurus) carapinus; and Gaevskajatrema halosauropsi n. sp. from Halosauropsis macrochir. The status of the nominal species of the genus Podocotyle Dujardin, 1845 is presented in annotated summary, along with a tabulation of the distinctive characteristics of recognised species of the genus. Gaevskajatrema Gibson & Bray, 1982 is discussed and its diagnosis amended.     

The Mouthparts in Some North Atlantic Species of the Genus Orchomene Boeck (Crustacea, Amphipoda)

The mouthparts of five North Atlantic species of the genus Orchomene have been studied in detail. The species are: O. serrata (Boeck, 1861), O. amblyops G. O. Sars, 1890, O. crispata (Goes, 1866). O. humilis (A. Costa, 1853) and O. pectinate. G. O. Sars, 1882. The structure of the mandibular molar has been studied with the aid of the scanning electron microscope. Some features of the mouthparts, common to the species examined, are interpreted as generic criteria which should justify retaining the genus Orchomene Boeck, 1870, separated from the closely related genera OrchomeneUa G. O. Sars, 1890, and Orchomenopsis G. O. Sars. 1891.     

Genetic differences within and between species of deep-sea crabs (chaceon) from the North Atlantic Ocean

The deep-sea red crab Chaceon quinquedens is a commercially important crustacean on the Atlantic continental shelf and slope of North America. To assess genetic subdivision in C. quinquedens, we examined the nucleotide sequence of the mitochondrial 16S rDNA gene and the internal transcribed spacers (ITS) of the nuclear ribosomal repeat in samples from southern New England and the Gulf of Mexico. We compared those data to sequences from two congeners, a sympatric species from the Florida coast, C. fenneri, and an allopatric eastern Atlantic species, C. affinis. The 16S rDNA data consisted of 379 aligned nucleotides obtained from 37 individuals. The greatest genetic difference among geographical groups or nominal species was between C. quinquedens from southern New England and C. quinquedens from the Gulf of Mexico. Haplotypes from these two groups had a minimum of 10 differences. All 11 C. fenneri samples matched the most common haplotype found in C. quinquedens from the Gulf of Mexico, and this haplotype was not detected in C. quinquedens from southern New England. The three haplotypes of C. affinis were unique to that recognized species, but those haplotypes differed only slightly from those of C. fenneri and C. quinquedens from the Gulf of Mexico. Based on 16S rDNA and ITS data, genetic differences between C. quinquedens from southern New England and the Gulf of Mexico are large enough to conclude that these are different fishery stocks. Our results also indicate that the designation of morphological species within the commercially important genus Chaceon is not congruent with evolutionary history. The genetic similarity of C. affinis from the eastern Atlantic and C. quinquedens from the Gulf of Mexico suggests these trans-Atlantic taxa share a more recent common history than the two populations of "C. quinquedens" that we examined.     

Diversity and distribution of single-stranded DNA phages in the North Atlantic Ocean

Knowledge of marine phages is highly biased toward double-stranded DNA (dsDNA) phages; however, recent metagenomic surveys have also identified single-stranded DNA (ssDNA) phages in the oceans. Here, we describe two complete ssDNA phage genomes that were reconstructed from a viral metagenome from 80 m depth at the Bermuda Atlantic Time-series Study (BATS) site in the northwestern Sargasso Sea and examine their spatial and temporal distributions. Both genomes (SARssφ1 and SARssφ2) exhibited similarity to known phages of the Microviridae family in terms of size, GC content, genome organization and protein sequence. PCR amplification of the replication initiation protein (Rep) gene revealed narrow and distinct depth distributions for the newly described ssDNA phages within the upper 200 m of the water column at the BATS site. Comparison of Rep gene sequences obtained from the BATS site over time revealed changes in the diversity of ssDNA phages over monthly time scales, although some nearly identical sequences were recovered from samples collected 4 years apart. Examination of ssDNA phage diversity along transects through the North Atlantic Ocean revealed a positive correlation between genetic distance and geographic distance between sampling sites. Together, the data suggest fundamental differences between the distribution of these ssDNA phages and the distribution of known marine dsDNA phages, possibly because of differences in host range, host distribution, virion stability, or viral evolution mechanisms and rates. Future work needs to elucidate the host ranges for oceanic ssDNA phages and determine their ecological roles in the marine ecosystem.     

Temperature tolerance and daylength effects in isolates ofScytosiphon lomentaria (Phaeophyceae) of the North Atlantic and Pacific Ocean

Fifteen geographical isolates ofScytosiphon lomentaria were investigated for their daylength response with regard to upright thallus formation, and nineteen isolates for their upper temperature tolerance. Six new day-neutral and two new photoperiodic strains were found. It became evident that day-neutral strains represent a common reaction group in this species, besides the photoperiodic group. The temperature regulation of photoperiodic and day-neutral strains did not show striking differences and it is assumed that temperature regulation may trigger seasonality of occurrrence in this species as well as photoperiod. The upper survival temperature after two weeks of heart stress is 28–29°C in all tested isolates. No temperature ecotypes were found.     

Histology of the fusion area between the parasitic male and the female in the deep-sea anglerfish Neoceratias spinifer Pappenheim, 1914 (Teleostei, Ceratioidei)

The article deals primarily with the histology of the fusion area between the head of the male and the skin of the female in two female Neoceratias spinifer, each of which had a single parasitic male attached. In this area, comprising the whole flattened upper part of the male head, the dermis of the male is completely fused with that of the female, leaving no remnants of the epidermis of either. In all other known cases permanent attachment of the parasitic male is accomplished by fusion of separate outgrowths from the male snout and lower jaw and the female skin. In the fusion area of N. spinifer two interconnected blood vascular plexus are present, the one located in the connective tissue of the male head, the other in that of the female skin. It is not known, however, whether the plexus in the female skin is provided with blood from the female blood vascular system, i.e. there is no critical proof of a real continuity between the female blood vascular system and that of the male. The eyes of both parasitic males are very degenerate. There is no histological evidence of degenerative changes in the male digestive system, heart or gills.     

Diversity of Diazotrophic Unicellular Cyanobacteria in the Tropical North Atlantic Ocean

We present data on the genetic diversity and phylogenetic affinities of N₂-fixing unicellular cyanobacteria in the plankton of the tropical North Atlantic Ocean. Our dinitrogenase gene (nifH) sequences grouped together with a group of cyanobacteria from the subtropical North Pacific; another subtropical North Pacific group was only distantly related. Most of the 16S ribosomal DNA sequences from our tropical North Atlantic samples were closely allied with sequences from a symbiont of the diatom Climacodium frauenfeldianum. These findings suggest a complex pattern of evolutionary and ecological divergence among unicellular cyanobacteria within and between ocean basins.     

Feeding ecology of the glacier lanternfish Benthosema glaciale (Actinopterygii, Myctophidae) in the Flemish Cap (North Atlantic Ocean)

The feeding dynamics of the glacier lanternfish Benthosema glaciale were studied during the summer of 2010 in the Flemish Cap. B. glaciale constituted a majority of the deep scattering layer (DSL), which was located between 300 and 650 m during daylight hours; at night, a part of the DSL migrated to the surface. B. glaciale is a zooplanktivore, feeding primarily on copepods (Calanus hyperboreus, Pareuchaeta norvegica, Metridia longa and Calanus finmarchicus), followed by amphipods (Themisto compressa) and krill (primarily Nematoscelis spp.). Although crustaceans dominated the diet, other invertebrates, such as chaetognaths, gastropods, polychaetes, ostracods and appendicularians, also contributed. The geographical differences in the composition of the diet resulted from the association of prey with distinct water masses. In the colder water at the north of the bank, Arctic species represented a higher proportion of the diet, but this situation was reversed in areas influenced by the warmer water from the south. B. glaciale fed more intensively towards the centre of the Flemish Cap. The diet of B. glaciale shifted ontogenetically, showing increasing prey size and prey diversity with increasing predator size.     

Description of phytoplankton and nutrient in spring in the western North Atlantic Ocean

Abundance of diatoms in the northern Sargasso Sea in springhas been observed in a 4-year period between 1981 and 1985 andthen again in 1987. A theory is presented that if stratificationblocks get-through of deep nutrients to the surface, as in thesouthern Sargasso, then in-situ cycling via non-diatoms andammonia dominates. The theory is that if in-situ cycling doesnot dominate, as northward, then stratification does not blockget-through of deep nutrients to the surface, which, in combinationwith the marked growth capacity of diatoms, produce an abundanceof cells. This abundance consumes nitrate, phosphate and silicateat the surface and ultimately this nutrient-depleted water arrivesin the southern Sargasso via the gyre circulation. Thus thenutrient-depleted water of the western Atlantic gyre is consideredto be primarily achieved only by diatoms, in spring and in thenorthern Sargasso. A transect during April 13–16, 1985,north from the Virgin Islands along 63°–64°W showsa great change in the diatom species plus Emiliania huxleyifrom negligible concentrations in the southern half of the sectionto large concentrations in the northern half. This unevennessof distribution can be rephrased by indicating that these speciesare narrow-niched with regard to nutrient availability. Theother species, coccolithophores and dinoflagellates, are evenlydistributed at low concentrations south-north (though some diminishslightly) and so they are broad-niched with respect to nutrient.High species diversity depends on broadness of nutrient nicheand equilibrium conditions of hydrographically stable water(i), implying that when non-equilibrium conditions occur (ii),when niche breadth is less (iii) or both (iv), then diversityis less marked, (i) is confirmed by broad-niched species southward,(ii) is confirmed by broad-niched species northward, (iii) isconfirmed by narrow-niched species southward and (iv) by narrow-nichedspecies northward.     

玉蝉花繁殖生态学研究

通过野外调查、人工授粉和室内种子萌发实验等,对天目山玉蝉花（Iris ensata）种群繁殖生态特征进行了研究。结果显示：玉蝉花自然种群呈聚集型分布,种群更新主要依赖贡献率为0.756的无性繁殖。人工同瓣和异瓣自花授粉座果率分别为10%和20%,结实数分别为0和4±1（n=2）粒/果;同株和异株异花授粉座果率分别为80%和100%,结实数分别为59±7（n=8）和64±9（n=10）粒/果,自交主要来自同株异花授粉,而同株花异熟、雌雄异位和异向等可有效降低自交。自然套袋不结实,不存在无融合生殖。花粉/胚珠比1277±270（n=10）,辅证玉蝉花为兼性异花授粉、异花授粉植物。有效授粉昆虫为蜜蜂（Apismellifica）,访花频率为0.019次.花-1.h-1,单只蜜蜂回访同朵花的比率为3.5%。自然种群立地种子数估算值为368粒/m2,种子宿存,具非深度生理休眠,萌发需光,低温层积60d萌发率达94.9±0.7%。玉蝉花种群繁殖适应对策为k对策,具备自我维持机制,但现正受人为干扰。     

Pollen distribution in the bottom sediments of the western North Atlantic Ocean

An extensive survey of pollen distribution in surficial sediments from the slope and rise between 29° and 72°N, shows patterns which reflect the distribution of vegetation in eastern North America and the effects of aeolian, fluvial, and marine sedimentation. The results of the analysis of 94 core tops show that pollen concentration ranges from 23,000 to 10 grains per gram, and decreases offshore with distance from vegetation sources and northward in relation to lower vegetation density. Maximum concentration occurs in organic-rich, fine-grained lutum deposited off rivers draining the southeastern United States. Low pollen concentrations are associated with high-energy environments, such as the Western Boundary Undercurrent and the Labrador Current. Percentages of dominant pollen types generally correspond with onshore distribution of pollen and vegetation. Oak and other deciduous pollen types are the most abundant in marine sediments off the deciduous forests of eastern United States. Hemlock pollen is essentially restricted to sediments off the hemlock-oak forests of northeastern U.S. and southeastern Canada, and spruce pollen is most abundant adjacent boreal forests and forest-tundra formations. The relative increase in pine pollen seaward reflects the selective effects of marine transport. Synthesis of pollen data by Q-mode factor analysis shows that major vegetation formations of eastern North America produce distinctive, regional marine pollen assemblages.