Characterization of 'safe sites' for pioneers in primary succession on recently deglaciated terrain

1 We characterized safe sites for individuals of five early colonizers ( Abies lasiocarpa , Juncus drummondii , J. mertensianus , Saxifraga ferruginea , S. tolmiei ) that had survived at least one growing season on the recently deglaciated forefront of the Lyman Glacier in the North Cascade Mountains, Washington, USA.
2 Sites with concave surfaces, coarse surface substrate and in the vicinity of large rocks were more likely to be colonized by pioneering plant species.
3 We speculate that the distribution of plants is determined by the presence of sites that facilitate seed trapping and protect seeds and seedlings from desiccation.
4 The data identify the abiotic factors that determine initial recruitment and spatial distribution of plants. Such controls precede biotic interactions in this primary successional sere.     

Genetic assessment of the effects of streamscape succession on coho salmon Oncorhynchus kisutch colonization in recently deglaciated streams

Measures of genetic diversity within and among populations and historical geomorphological data on stream landscapes were used in model simulations based on approximate Bayesian computation (ABC) to examine hypotheses of the relative importance of stream features (geomorphology and age) associated with colonization events and gene flow for coho salmon Oncorhynchus kisutch breeding in recently deglaciated streams (50–240 years b.p .) in Glacier Bay National Park (GBNP), Alaska. Population estimates of genetic diversity including heterozygosity and allelic richness declined significantly and monotonically from the oldest and largest to youngest and smallest GBNP streams. Interpopulation variance in allele frequency increased with increasing distance between streams (r = 0·435, P < 0·01) and was inversely related to stream age (r = –0·281, P < 0·01). The most supported model of colonization involved ongoing or recent (<10 generations before sampling) colonization originating from large populations outside Glacier Bay proper into all other GBNP streams sampled. Results here show that sustained gene flow from large source populations is important to recently established O. kisutch metapopulations. Studies that document how genetic and demographic characteristics of newly founded populations vary associated with successional changes in stream habitat are of particular importance to and have significant implications for, restoration of declining or repatriation of extirpated populations in other regions of the species' native range.     

Anatomical, morphological and ecophysiological strategies in Placopsis pycnotheca (lichenized fungi, Ascomycota) allowing rapid colonization of recently deglaciated soils

The green algal lichen Placopsis pycnotheca was identified at Pia and Marinelli glaciers (Isla Grande of Tierra de Fuego, Chile) as a primary colonizer of bare soil in areas close to the front of the glacier or around small ponds created after glacier retreatment. Electron microscopy study showed that P. pycnotheca formed a thick hypothallus within which hyphae and their extracellular polymeric substances bind numerous soil particles. This structure augments water holding and soil stabilization capacities and constitutes an early stage in soil crust development. In addition, numerous cephalodia are formed within the hypothallus and subsequently develop upwards towards the thallus surface, sometimes before the formation of squamules with green algae. These anatomical and morphological strategies together with physiological properties such as the long photosynthetic activity period (measured in the laboratory) help explain its pioneering role as a colonizer and its apparently high growth rate.     

Microbial community succession and bacterial diversity in soils during 77,000 years of ecosystem development

The origins of the biological complexity and the factors that regulate the development of community composition, diversity and richness in soil remain largely unknown. To gain a better understanding of how bacterial communities change during soil ecosystem development, their composition and diversity in soils that developed over c. 77 000 years of intermittent aeolian deposition were studied. 16S rRNA gene clone libraries and fatty acid methyl ester (FAME) analyses were used to assess the diversity and composition of the communities. The bacterial community composition changed with soil age, and the overall diversity, richness and evenness of the communities increased as the soil habitat matured. When analysed using a multivariate Bray-Curtis ordination technique, the distribution of ribotypes showed an orderly pattern of bacterial community development that was clearly associated with soil and ecosystem development. Similarly, changes in the composition of the FAMEs across the chronosequence were associated with biomarkers for fungi, actinomycetes and Gram-positive bacteria. The development of the soil ecosystem promoted the development of distinctive microbial communities that were reminiscent of successional processes often evoked to describe change during the development of plant communities in terrestrial ecosystems.     

Colonization and succession of macroinvertebrates in recently freshened Lake Volkerak-Zoom (The Netherlands)

Macroinvertebrates were studied during the first five years after closure and freshening of the lake system Volkerak-Zoom, two lakes interconnected by a channel. Before embankment, in 1987, these lakes were part of the tidal eastern Scheldt estuary in the south-western part of the Netherlands. Four months after embankment, the first freshwater species were found. In general, the colonization process followed the same pattern as was reported for newly created reservoirs. In Lake Volkerak-Zoom differences in colonization time were observed between distinguished depth zones. Within the chironomid assemblages, dominance of Chironomus muratensis was followed by a dominance of Procladius, Glyptotendipes and Cladotanytarsus. The succession was related to changes in phytoplankton concentrations. Although in 1991 changes in macrofauna composition were less pronounced as compared to previous years, succession was still going on.     

The role of spontaneous vegetation succession in ecosystem restoration: A perspective

Abstract. The paper summarizes ideas which were discussed during the ‘Spontaneous Succession in Ecosystem Restoration’ conference and elaborated through further discussion among the authors. It seeks to promote the integration of scientific knowledge on spontaneous vegetation succession into restoration programs. A scheme illustrating how knowledge of spontaneous succession may be applied to restoration is presented, and perspectives and possible future research on using spontaneous vegetation succession in ecosystem restoration are proposed. It is concluded that when implementing spontaneous succession for ecological restoration the following points must be considered: setting clear aims; evaluation of environmental site conditions; deciding whether spontaneous succession is an appropriate way to achieve the aims; prediction of successional development; monitoring of the results. The need for interdisciplinary approaches and communication between scientists, engineers and decision‐makers is emphasized.     

The effect of a seed source on primary succession in a forest ecosystem

An analysis of the Relative Importance Value Index (RIVI) of later successional tree species and the Shannon diversity indexH of all tree and shrub species was undertaken on previously mined sites within a sparsely forested area in central Florida, USA. A comparative analysis of the distance to a seed source and the age of a site suggested that the distance to a seed source was the best predictor (R ²=0.85) of the regeneration of the later successional species and a good predictor of species diversity. Both theRIVI of the later successional species and the diversity index decreased with the distance from the seed source. The lack of a seed source containing climax species resulted in arrested succession at some sites. It is suggested that biological information is the causative means of succession and the dispersal of this information entails spatial dependency while its introduction and development are time dependent processes.Research was part of a project of the Center for Wetlands, University of Florida, Gainesville under contract with the Florida Institute of Phosphate Research. Interactions of Wetlands with Phosphate Mining, H. T. Odum and G. R. Best, principal investigators. B. T. Rushton, J. Butner, G. R. Best, R. S. Schnoes and S. R. Humphrey are thanked for the use of their data.     

The postcranial anatomy of Suminia getmanovi (Synapsida: Anomodontia), the earliest known arboreal tetrapod

The basal anomodont Suminia getmanovi Ivakhnenko, 1994 from the late Palaeozoic of Russia is highly specialized in its masticatory apparatus, and has been suggested to represent the earliest arboreal tetrapod in the fossil record. Its postcranial anatomy is described in detail for the first time, revealing a large number of autapomorphies for this small herbivore. These include a reduced number of presacral and therein dorsal vertebrae, an elongate neck, a long and possibly prehensile tail, a procoracoid with a notch at its ventromedial margin rather than a foramen, an iliac blade with a robust ridge at its anteromedial edge, a pubis with a puboischiadic fenestra and separate pubic foramen, and elongate limbs. Additional autapomorphic characters are displayed in the autopodium, which comprises about 40% of the entire limb length. These features include an enlarged, phalangiform distal carpal 1 and tarsal 1, a short and robust first metacarpal, a crescent‐shaped distal tarsal 4, and elongate penultimate phalangeal elements. The phylogenetic relationships of basal anomodonts are revisited using an expanded data set, with the addition of key taxa and several postcranial characters. Unlike dicynodonts, Suminia retained the plesiomorphic phalangeal formula for amniotes of 2‐3‐4‐5‐3 (manus) and 2‐3‐4‐5‐4 (pes). This pattern is achieved by the retention of disc‐like phalangeal elements between the proximal and penultimate phalanges in digits III, IV (manus and pes), and V (pes only). In light of the new material, Suminia can be recognized as the most complete basal anomodont, offering new insights into the early evolution of the group. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 661–698.     

The earliest stages in the development of the circulatory system of the Rainbow Trout Oncorhynchus mykiss

The older literature suggests that the development of the blood vascular system in teleosts differs from that of other vertebrates. The evidence, however, came mostly from studies of salmonid embryos beyond the stages when blood cells had begun to circulate, which overlooked earlier developmental stages. The development of the blood vessels of the rainbow trout are illustrated from the time of the first heartbeat to the stage of eye pigment formation. Unless they can be injected with a dye solution, the earliest vessels to develop remain invisible until blood flow makes them visible. By the time of the first heartbeat stage, the embryo has a dorsal aorta, caudal artery and vein, a few transverse vessels, and even the beginning of a vitelline network. One feature peculiar to teleosts is the development of the intermediate cell mass, from which the erythrocytes and a temporary capillary network are formed rather than from the yolk sac. Development of the early posterior cardinal and the subintestinal vein occurs much as in other vertebrates. Previous investigators missed these earliest phases of development because of the difficulty of making them visible. Early formation and transformation of the vascular system of the rainbow trout generally conforms to that seen in vertebrates, except as modified by the temporary presence of the intermediate cell mass and the specialized teleostean yolk mass. With the reduction of the intermediate cell mass, the primary circulatory system for yolk utilization is transformed into a secondary one for respiratory and metabolic functions, as happens usually among vertebrates. J. Morphol. 233:215–236, 1997. © 1997 Wiley-Liss, Inc.     

MYP基因在中间球海胆及杂交海胆生殖腺不同发育时期的转录表达差异

摘要: 应用实时荧光定量PCR技术对主要卵黄蛋白(Major yolk protein, MYP)基因在中间球海胆和杂交海胆(中间球海胆♀×光棘球海胆♂)的生殖腺不同发育时期的转录表达差异进行了分析。结果表明, MYP基因在海胆雌雄个体生殖腺中转录水平上的表达差异不明显; MYP基因在中间球海胆生殖腺发育的4个时期的表达呈快速下降的趋势, 而在杂交海胆呈缓慢下降的趋势。在分析的生殖腺4个发育期中, 中间球海胆雌雄个体 MYP 基因的表达量(以18S rRNA为参照)分别从44.55%和41.17%下降到9.59%和1.83%; 杂交海胆的雌雄个体分别从37.66%和36.66%下降到19.22%和12.55%。MYP基因的转录表达量差异与杂交后生殖腺产生的变异密切相关。     

Vitamin E in early stages of sea bass (Dicentrarchus labrax) development

This study reports titration of vitamin E levels in the sea bass (Dicentrarchus labrax) using high-pressure liquid chromatography. The first part of the work is devoted to vitamin E detection in: (1) plasma of maturing females and males characterized by different body sizes; (2) seminal fluid and eggs; and (3) developing embryos of sea bass fed with vitamin E. In the second part of the study, variations of vitamin E levels during larval development are analyzed. The results show a direct correlation between plasma vitamin E content and body size for both adult male and female sea bass. High vitamin E levels were found in seminal fluid, in eggs before and after fertilization, and in embryos during development and at hatching, whereas vitamin E level was low in dead embryos and in embryos with limited survival. During larval development, the vitamin E content decreased slowly but steadily during the first four days of larval growth; subsequently, it progressively increased from day 9 to day 40. In teratogenic larvae, vitamin E content was significantly higher than in normal larvae. This study provides evidence on how vitamin E exerts an antioxidant defense in sea bass reproduction.     

The earliest stages of adaptation in an experimental plant population: strong selection on QTLS for seed dormancy

Colonizing species may often encounter strong selection during the initial stages of adaptation to novel environments. Such selection is particularly likely to act on traits expressed early in development since early survival is necessary for the expression of adaptive phenotypes later in life. Genetic studies of fitness under field conditions, however, seldom include the earliest developmental stages. Using a new set of recombinant inbred lines, we present a study of the genetic basis of fitness variation in Arabidopsis thaliana in which genotypes, environments, and geographic location were manipulated to study total lifetime fitness, beginning with the seed stage. Large‐effect quantitative trait loci (QTLs) for fitness changed allele frequency and closely approached 90% in some treatments within a single generation. These QTLs colocated with QTLs for germination phenology when seeds were dispersed following a schedule of a typical winter annual, and they were detected in two geographic locations at different latitudes. Epistatically interacting loci affected both fitness and germination in many cases. QTLs for field germination phenology colocated with known QTLs for primary dormancy induction as assessed in laboratory tests, including the candidate genes DOG1 and DOG6. Therefore fitness, germination phenology, and primary dormancy are genetically associated at the level of specific chromosomal regions and candidate loci. Genes associated with the ability to arrest development at early life stages and assess environmental conditions are thereby likely targets of intense natural selection early in the colonization process.     

The management of populations of vesicular-arbuscular mycorrhizal fungi in acid-infertile soils of a savanna ecosystem

Topsoil stockpiled for 4 years resulted in an accumulation of NH₄-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below 1m. Both NH₄-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen.Stockpiled soil which underwent an ammonium-rich perfusion regime in the laboratory indicated that in-mound soils rapidly attained greater nitrification potential than surface mound soils and also had greater potential for further mineralisation of organic matter to NH₄-N. This further production was seen as a contribution from the bacterial flush, stimulated by the large labile-C pool already present.As the bulk of stored soil was anaerobic, restored soils were seen as potentially wasteful of their N-reserves; the fate of nitrogen and soluble carbon compounds in restored soils is discussed.     

The management of populations of vesicular-arbuscular mycorrhizal fungi in acid-infertile soils of a savanna ecosystem

A field trial was conducted at two sites in the savanna ecosystem of eastern Colombia to compare the effects of inoculation with vesicular-arbuscular mycorrhizal fungi (VAMF) ofBrachiaria dictyoneura (a tropical grass), cassava (Manihot esculenta), the tropical forage legume kudzu (Pueraria phaseoloides) andSorghum sp., and two phosphate sources. The second stage of the trial studied the effect of these pre-crop treatments on the subsequent growth, nutrition and VAM status of cowpea (Vigna unguiculata) andStylosanthes capitata in the following season, compared with both crops sown in native savanna. Inoculation significantly increased the levels of VAM and plant yields in the early growth stages of all crops during the first season, particularly with the rock phosphate (RP) source. The most significant increases were observed in the mycorrhiza-dependent cassava and kudzu crops up to 15 weeks after sowing, and were associated with increased foliar uptake of P and Mg. The effectiveness of the introduced inoculum was greater at the field site with a sandier soil. In the second season the levels of VAM in roots of cowpea andS. capitata were all increased significantly in pre-cropped plots compared with a savanna control. The increased presence of VAM was associated with significantly increased yields on plots previously sown to cassava, kudzu andSorghum sp. The data support the idea that increasing the VAMF inoculum potential of these acid-infertile soils by inoculation or pre-crops can greatly increase the rate of establishment of mycorrhiza-dependent host plants.     

The zoeal stages and megalopa of Portunus rubromarginatus (Lanchester) (Decapoda: Portnnidae), reared in the laboratory

The present state of knowledge concerning Portunus larvae isreviewed, and the three zoeal and the megalopa stages of P.rubromarginatus are described and figured. Details of appendagesetation are tabulated. This species is unusual amongst knownPortunus spp. in having only three zoeal stages and, like otherPortunus spp. but in contrast with other Portuninae, it has4 + 4, or 4 + 1 + 4, setae on the posterior telson border. When compared with larvae of the five other Indo-West PacificPortunus species whose larvae are known P. rubromarginatus zoeaeare readily distinguished from all, except P. hastatoides, usingthe key features given by Kurata (1975). Comparison was madebetween first zoeae of these two species, and also of P. pelagicusand P. sanguinolentus, using larvae reared by the authors. Itwas found telson characters alone allow distinction betweenlarvae of these four species. These characters are tabulated. P. rubromarginatus megalopae differ from those known for congenitorsin having a large spine on the uchium of the first pereiopod,but not on the carpus, and in having relatively very small sternalcornuae. Several of these features disagree with those previously thoughtto characterise larval Portuninae or Portunus species.     

Molecular dating of a marine species,Eriocheir japonica (Decapoda: Grapsidae), corroborates cenozoic tectonic events and sea level fluctuation

Changes of coastal topography for Cenozoic Himalayan orogeny complicated the phylogeographical structure of marine species and deepened their divergences. To test the association between divergence and Cenozoic tectonic events, we analyzed the phylogeographical structure of Eriocheir japonica by combining molecular data and geographical environment events. The four distinct lineages obtained through phylogenetic reconstruction and network analysis demonstrated the significant genetic divergence among geographical populations. Furthermore, the divergence time between E. j. japonica in Japan and E. j. sinensis in China was about 10.5–11.5 mya, which was coincident with the opening of the Sea of Japan. The north-south divergence time (15.5–17.5 mya) was in the range of the occurrence of the Himalaya movement. We hypothesize that coastal topography, including the formation of Taiwan in the Himalaya movement and the opening of the Sea of Japan, contributed to the geographical subspeciation of marine species. Mitten crabs were inferred to originate from one ancient population with the oldest haplotype H6 and subsequently divide into northern and southern populations. Furthermore, the Japan lineage derived from northern population in China for the opening of the Sea of Japan.     

长白山不同演替阶段森林植物功能性状及其与地形因子间的关系

植物功能性状是近年来生态学研究的热点。不同种群功能性状的差异决定竞争优势,导致群落结构和性质发生改变,进而演替。以长白山森林演替过程中4个阶段的典型群落为研究对象,分析了长白山地区森林不同层次优势种的茎叶功能性状之间的关系、功能性状与地形因子的关系,并对不同演替阶段群落功能性状进行了比较。结果发现,比叶面积(SLA)与叶氮浓度(LNC)和茎磷浓度(SPC)正相关,与叶干物质质量(LDMC)负相关;叶厚度(LT)与LDMC负相关;LNC与LPC、SNC和LDMC呈正相关;茎氮浓度(SNC)与茎磷浓度(SPC)正相关;茎组织密度(STD)与LNC、SNC正相关。通过灰色关联度分析发现,海拔对SLA、LNC、LPC、STD、SPC影响最大;坡向对于LT、LDMC影响最大;坡位对SNC影响最大。各演替群落间的乔木层功能性状均有显著差异,灌木层的功能性状无显著差异,而草本层除了LDMC、LPC、SNC有显著差异外,其它指标均无显著差异;SLA、STD、LNC随演替的进行呈现明显增加趋势,LDMC、LPC随演替呈减少的趋势。LDMC和SLA是能体现群落演替差异的主要功能性状。