A Race for Space? How Sphagnum fuscum stabilizes vegetation composition during long‐term climate manipulations

Strong climate warming is predicted at higher latitudes this century, with potentially major consequences for productivity and carbon sequestration. Although northern peatlands contain one‐third of the world's soil organic carbon, little is known about the long‐term responses to experimental climate change of vascular plant communities in these Sphagnum‐dominated ecosystems. We aimed to see how long‐term experimental climate manipulations, relevant to different predicted future climate scenarios, affect total vascular plant abundance and species composition when the community is dominated by mosses. During 8 years, we investigated how the vascular plant community of a Sphagnum fuscum‐dominated subarctic peat bog responded to six experimental climate regimes, including factorial combinations of summer as well as spring warming and a thicker snow cover. Vascular plant species composition in our peat bog was more stable than is typically observed in (sub)arctic experiments: neither changes in total vascular plant abundance, nor in individual species abundances, Shannon's diversity or evenness were found in response to the climate manipulations. For three key species (Empetrum hermaphroditum, Betula nana and S. fuscum) we also measured whether the treatments had a sustained effect on plant length growth responses and how these responses interacted. Contrasting with the stability at the community level, both key shrubs and the peatmoss showed sustained positive growth responses at the plant level to the climate treatments. However, a higher percentage of moss‐encroached E. hermaphroditum shoots and a lack of change in B. nana net shrub height indicated encroachment by S. fuscum, resulting in long‐term stability of the vascular community composition: in a warmer world, vascular species of subarctic peat bogs appear to just keep pace with growing Sphagnum in their race for space. Our findings contribute to general ecological theory by demonstrating that community resistance to environmental changes does not necessarily mean inertia in vegetation response.     

Behavioural responses of native predators to an invasive toxic prey species

One important impact of invasive species may be to modify the behaviour of native taxa. For example, the invasion of highly toxic cane toads (Bufo marinus) kills many anurophagous native predators, but other predators learn to recognize and avoid the toxic invader. We exposed native fish (northern trout gudgeons, Mogurnda mogurnda) and Dahl's aquatic frogs (Litoria dahlii) to cane toad tadpoles, then monitored the predator's responses during subsequent trials. Both the frogs and fish initially attacked toad tadpoles, but rapidly learned not to do so. Fish and adult frogs retained their aversion for at least a week, whereas recently metamorphosed frogs did not. Clearly, the spread of cane toads through tropical Australia can modify feeding responses of native aquatic predators. For predators capable of rapid avoidance learning, the primary impact of cane toads may be on foraging behaviour rather than mortality.     

Head Ectodermal Patterning and Axial Development in Frogs

Two transient glands, the hatching and cement glands, definecritical boundaries on the head of the frog embryo. They canbe used to monitor formation of the head, which in turn is asensitive indicator of development of the dorsal axis, characteristicof chordates. Experimental treatment of embryos generates avariety of head abnormalities. Alteration of inductive patternscan produce large heads (macrocephaly), and comparable alterationsmay yield new phenotypes naturally. Several paths lead to decreasedhead development, and one of these may mimic in reverse thepath which led to the evolution of the vertebrate head.     

The expression of histone 2A in onion (Allium cepa) during the onset of dormancy, storage and emergence from dormancy

The tissue-specific and developmental expression of histone 2A was studied in onion ( Allium cepa 'Robusta'), using northern blots. Histone 2A expression was enriched in basal tissues, particularly in the inner, meristematically active parts of bulbs. The expression was assessed during a time course of bulb development, dormancy onset and post-harvest sprouting in field-grown material. During bulb development histone 2A expression in the inner bulb declined rapidly during bulb ripening, reaching a minimum with the onset of dormancy. During post-harvest storage, expression increased slowly, reaching a peak in the spring, coinciding with the first observed sprout emergence. It was concluded that in onion, as in other plant systems, histone 2A expression is linked to cell division and dormancy level, the peak in expression during post-harvest storage indicating the time of dormancy breakage. In cultivars where post-harvest sprouting occurred much earlier or much later than in 'Robusta', this expression peak occurred at about the same time of year, regardless of sprouting time. It was concluded that differences in storage longevity between cultivars were not due to differing times of dormancy breakage. Factors controlling the rate of sprout emergence post-dormancy are likely to be major determinants of storage capacity.     

Interaction between floral color change and gender transition in the protandrous weed Saponaria officinalis

Natural selection has directed the evolution of floral traits so that pollinator visits are manipulated to maximize the fitness of individual plants by directing which other individual sires its seeds. In some plants, flowers change color over time and may have the ability to direct pollinators to rewarding flowers. In addition, by varying when pollen is available and when stigmas are receptive, protandrous plants can show variation in selfing rates. In this study, the association between color change and gender transition in flowers of Saponaria officinalis was examined. Anthocyanins were extracted from flowers of each gender stage to measure color using spectrophotometry. Female‐phase flowers were found to have significantly higher anthocyanin concentration than male‐phase flowers in both natural populations and experimental plots. This color change corresponded to a decrease in male sexual function, which was measured by the percentage of pollen grains stained as viable by lactophenol aniline blue and germinated on Brewbaker–Kwack media. Color change was phenotypically plastic. Plants grown in full sun had a more extensive color change than those grown in shaded experimental plots, and this effect was reversed the following year when the shading was removed. Pollinator observations documented both diurnal and nocturnal insect visitation. Fruit and seed set were equivalent on inflorescences bagged during daylight versus night, indicating that both diurnal and nocturnal insects are effective pollinators. If pollinators discriminate based on color, this could potentially reduce within‐plant floral visits and also geitonogamy. This study is the first to document flower color change and moth pollination in Saponaria officinalis.     

The potential trade‐off between artisanal fisheries production and hydroelectricity generation on the Kafue River,Zambia

1. Freshwater resource managers are increasingly obligated to consider the impacts of large river engineering projects on ecosystem services. We evaluated the effect of altered water regime from the operation of a large dam on the production of the downstream tropical floodplain fishery of the Kafue River, Zambia. We compared the benefits of increased hydropower relative to potentially lost fishery production. 2. We compiled a long‐term data set consisting of experimental gillnet catches, artisanal harvesting effort and monthly river flows for 25 years prior to and 29 years after the 1977 completion of the upstream Itezhi‐Tezhi Dam. As a metric of the flood regime, we calculated a canonical correlation score for each hydrological year before and after dam closure. For the period following dam construction, we used the Muskingum method of flood routing to estimate ‘no‐dam’ flows through the fishery area and downstream hydroelectric turbines at the Kafue Gorge Dam. 3. We compared 16 alternative models of catch per unit effort (CPUE) with and without an effect of water regime on fish population growth rate. Using the two best fitting models, we estimated the total observed fishery harvest and simulated ‘no‐dam’ fisheries harvest and found no significant effect of altered water regime on fishery production. 4. We estimate that the large upstream dam increases downstream hydropower production by about $18 million USD per annum. The reduction in fishery production caused by the altered water regime is not significantly different than zero, although the average reduction amounts to about $2.3 million annually. The total estimated value of harvest ranges from $1.3 million to $56 million annually. 5. Large observed declines in fish abundance over the 54‐year study period are attributed primarily with similarly large increases in total fishing effort in this mostly open‐access artisanal fishery. 6. These results contrast with other examples of the effects of flow alteration on fish, probably because levels of fisheries exploitation on the Kafue River are very high relative to better studied regions on other continents; our focus on the whole fish community; and the unprecedented length of the time series we considered. If the goal is to sustain fishery production, investments in altering flow regime are likely to be less effective than investments to decrease fishing effort.     

Processes affecting newly-settled juveniles and the consequences to subsequent community development

Summary

Processes affecting the growth and mortality of the juvenile benthic life-stages that immediately follow larval metamorphosis and settlement are as important as those processes controlling the supply of settling larvae or later interactions among established adults. In addition, the ecology of juveniles is of ten distinctly different from that of other life-stages, including differences in interactions with predators and competitors and responses to the physical environment. In particular, newly-settled stages of ten experience quantitatively or qualitatively different predation than older life-stages. We have documented this in a New England hard substrate community where the wrasse, Tautogolabrus adspersus, and two species of tiny gastropods, Mitrella lunata and Anachis lafresnayi, prey on newly-settled andjuvenile ascidians but not on adults. An extensive series of field experiments was conducted using artificial pilings placed subtidally. Results demonstrated that (1) the predators were extremely active and fairly specific in their prey, (2) predators could eliminate prey species regardless of settlement densities, (3) predation varied drastically with life-stage, and (4) predators control community structure and composition by altering the number of settling larvae that survived their first several weeks to become identifiable recruits. Because of differences in predator abundances the development and species dominance within the community varied drastically between sites.     

NaCl胁迫下黑果枸杞转录组测序分析

研究黑果枸杞在不同浓度盐胁迫下基因表达谱变化情况,为进一步研究黑果枸杞抗盐分子机制奠定研究基础。对0(CK)、50、250 mmol/L NaCl溶液胁迫的黑果枸杞组培苗的根和叶在胁迫时间为0、1、12 h时分别取样,采用转录组测序(RNASeq)技术进行测序分析。结果表明,转录组测序共产生222.49 Gb原始数据,拼接出Unigenes 86 037条,注释到7大功能数据库(GO、KEGG、KOG、NR、Pfam、Swiss-Prot和egg NOG)上的Unigenes总数为46 594个,占总Unigenes的54.76%,还有38 929个Unigenes在这些数据库中没有得到注释。通过GO分类和KEGG Pathway富集性分析,分别归于51个GO类别和211条代谢途径。差异表达基因分析显示,黑果枸杞叶片和根的上调基因和下调基因数随着NaCl浓度的增大和处理时间的延长均呈增加趋势,叶片中的上调基因数(7 514)小于下调基因数(9 032),根中的上调基因数(12 347)大于下调基因数(11 559)。在黑果枸杞盐胁迫下转录组中发现28 325个SSR位点,最多的为单核苷酸SSR,占70.47%。综合分析表明,黑果枸杞对盐胁迫的反应是一个多基因参与、多个生物过程协同调控的过程,基因表达量的变化可能是基因调控的主要方式。