Coupling of nauplii release in barnacles with phytoplankton blooms: a parallel strategy to that of spawning in urchins and mussels

We examined the coupling between the release of nauplii in Semibalanusbalanoides and phytoplankton blooms, and compared it with themechanism synchronizing spawning with phytoplankton abundancein green sea urchins (Strongylocentrotus droebachiensis) andblue mussels (Mytilus edulis). Close contact with phytoplanktoncells is required to stimulate the release of nauplii in Semibalanus,whereas spawning in urchins and mussels is triggered by an extracellularmetabolite of phytoplankton. The response is concentration dependentand positively correlated with the frequency of moulting Themoulting rate in Semibalanus is reported to be directly correlatedwith food intake and thus larval release should be proportionalto feeding activity. The release of Semibalanus nauplii is morestrongly stimulated by the diatom Skeletonema costatum thanby Phaeodactylum tricornutum, whereas the highest response isobtained in treatments with nauplii of Artemia salina. We suggestthat these differences are related to size of the planktonicparticles (Artemia nauplii < Skeletonema < Phaeodactylum)Exposure to air, as occurs in the intertidal zone, does notinfluence significantly larval release Larval release in otherCrustacea may similarly be coupled to phytoplankton abundance.     

Ecological hindcasting of biogeographic responses to climate change in the European intertidal zone

Intertidal organisms are often assumed to live close to their thermal limits, and have emerged as potential early indicators of the effects of climate change. We compared our survey of the 2004–2006 geographic distribution of the barnacle Semibalanus balanoides to its distribution in 1872, 1955, 1963, 1971, and 1985, from surveys by Fischer, Crisp, Fischer-Piette, Barnes, Powell, and Southward. The southern geographic limit has retreated 300 km in France since 1872, at a rate of 15 to 50 km per decade. We compared our 2006 survey of the geographic distribution of the polychaete Diopatra neapolitana to its distribution in 1893–1923, from surveys by Saint-Joseph and Fauvel, and its distribution in 1969–1976 from surveys by Glémarec. The northern geographic limit of this species has advanced 300 km in France since 1893 at similar rates to Semibalanus. We used NOAA weather reanalysis data and our mechanistic simulation model of intertidal animal body temperatures to hindcast the thermal environmental change near historical geographic limits in Europe for the past 55 years. Results indicate that changes in the southern limit of S. balanoides are due to intolerance of winter body temperatures above 10°C, leading to reproductive failure. Results for Diopatra are ambiguous: based on the northern extension of its range, either cold winters or cool summers limit its range, while gaps in its distribution are consistent with limitation by cooler summer conditions. The parallel shifts of D. neapolitana on sedimentary shores and Semibalanus on rocky shores suggest that similar climatic factors control the geographic limits of both species. The intertidal zone is a model system for examining the effects of climate change on biogeographic change both because of the rapidity of its response, and because the rich historical record allows direct tests of hypotheses. Guest editors: J. Davenport, G. Burnell, T. Cross, M. Emmerson, R. McAllen, R. Ramsay & E. Rogan Challenges to Marine Ecosystems     

Supply-side control over the survivorship of Chthamalus spp. recruits in northern Baja California

The constant supply of larvae to coastal habitats is important for the persistence of populations and can vary depending on oceanic conditions that may affect physical transport processes. We evaluated the survivorship of Chthamalus recruits in Playa San Miguel, Baja California, for over a year to evaluate if the supply of new recruits was of greater importance than the post-recruitment factors of competition and predation in determining adult population size. We hypothesized that the number of Chthamalus recruits would predict the number of adults present and that predation and competition would not play a significant role in determining adult densities. Recruit density was a robust predictor of adult density despite the presence of weak density-dependent mortality. Neither predation nor competition significantly affected the survivorship of recruits and did not decouple the relationship between recruit and adult densities, suggesting that these post-recruitment controls did not play an important role in determining the population size of Chthamalus barnacles at this site. The data support the hypothesis that supply-side control is the primary factor structuring the population of Chthamalus in the intertidal community at Playa San Miguel.     

Flowers, Nectar and Insect Visits: Evaluating British Plant Species for Pollinator-friendly Gardens

Twenty-four plant species native or naturalized in Britain weregrown in the Cambridge University Botanic Garden, UK and evaluatedas potential resources for nectar-foraging bees, butterfliesand hoverflies. In ten plant species a series of measurementswere made, at regular intervals from dawn to dusk, of nectarsecretion rate and standing crop, and in all species insectvisits were monitored throughout daylight hours. The study revealeddifferences between plant species in the composition of theassemblage of insect visitors, and in the magnitude and temporaldistribution of the nectar reward. In some cases we found interestingcorrelations between temperature and secretion rates or patternsof insect visits. Species that received numerous insect visitsin our study are potentially valuable forage plants that mightbe planted by gardeners to support local pollinator populations.Deep flowers whose nectar is accessible to long-tongued bumblebees(Bombus hortorum, B. pascuorum) but not to honeybees may providelong-tongued pollinators with a resource refuge relatively freefrom honeybee competition. Features that make some of thoseplant species particularly interesting to observe in the gardeninclude robbing by short-tongued bumblebees inSaponaria,baseworkingby honeybees on closed flowers inMalva sylvestris, and apparentdisplacement of bumblebees by territorial behaviour of the solitarybeeAnthidium manicatumon species ofStachys.Copyright 1999 Annalsof Botany Company Wild flowers, gardens, nectar,Silene, Lychnis, Saponaria, Stachys, Malva, Dipsacus fullonum, Lythrum salicaria,pollinators, bumblebees,Bombus,honeybees,Apis,butterflies, Lepidoptera, hoverflies, Syrphidae,Anthidium manicatum, weeds.     

Spontaneous Chromosome Breakage in Lilium Endosperm

Abnormal mitoses, resulting from chromosome breakage and reunion,occurred in Lilium regale and in the hybrid L. ‘PhyllisCox’ 4 weeks after fertilization. The abnormalities appearedto commence with a single chromatid bridge and in ‘PhyllisCox’ abnormalities accumulated resulting in the formationof multiple bridges, ring chromosomes, fragments, dicentricchromosomes, and micronuclei. Failure of anaphase separationfollowed by restitution resulted in the formation of highlypolyploid nuclei in which mass spontaneous chromosome breakageoccurred. The accumulation of abnormalities in the hybrid endosperm reducedthe mitotic activity and culminated in the failure of the endosperm.This led to the death of the otherwise normal embryo. This sequenceof events is probably of wide importance in the failure of interspecifichybridization.     

Character States of Development and Initiation of Cohesion between Compound Pollen Grains of Acacia paradoxa

Cytoplasmic channels link Acacia paradoxa micropores until callosespecial wall dissolution, and do not provided templates forwall bridge formation in the future polyad. Wall bridges formby a unique mechanism. Endexine bridges on radial walls betweenadjacent microspores form from wrist-like bosses of endexineflanking the germinal apertures. Acacia microspores are alsounique in lacking a growth and vacuolation period prior to mitosis,with the surface area of the cytoplasm only increasing by 28%during development. The character states of polyad developmenthave been defined, and confirm the unusual states of pollendevelopment and provided a basis for future phylogenetic analysis.Copyright1993, 1999 Academic Press Microspore growth, polyad, Mimosaceae, exine, wall bridges     

Allometry and Competition between Saplings of Picea jezoensis and Abies sachalinensis in a Sub-boreal Coniferous Forest, northern Japan

The crown shape and the mode of competition between saplings(<2m in height) of the two conifers,Picea jezoensis andAbiessachalinensis, of a sub-boreal forest, northern Japan, wereinvestigated based on the diffusion model. A model for individualsapling growth considering both inter- and intraspecific competitionwas developed. The effect of species-specific crown shape onthe sapling growth and competition of the two species were examined.PiceajezoensisandAbies sachalinensissaplings had deep conic and shallowflat crowns, respectively.Picea jezoensishad more foliage massthanAbies sachalinensisof the same sapling mass. It was suggestedthat thePicea jezoensissapling has a high cost for assimilation–respirationbalance under dark conditions of closed canopies, whereas theAbiessachalinensissapling maintains effective assimilation even undersuppressed conditions. Widely spaced saplings, such as gap successors,ofPicea jezoensishad a greater relative growth rate (a₀) thanwidely spacedAbies sachalinensis. The crown shape of saplingsof the two species shows different adaptations for efficientpersistence in the sub-boreal forest. Saplings ofPicea jezoensisandAbies sachalinensiswere not uniformlydistributed, but aggregated in different sites as the saplingsgrew, indicating habitat segregation between the two speciesat the sapling stage. Intraspecific sapling competition wasone-sided in each of the two conifers. Interspecific saplingcompetition was one-sided in the direction only fromAbies sachalinensistoPiceajezoensis. Therefore, asymmetric competition prevailed at thesapling stage of the two species. These results contrast withweak symmetric competition or the almost absence of competitionbetween trees (2m in height) of the two species (Kubota andHara,Annals of Botany76: 503–512, 1995). The mode of competitionchanged with the life-history stage from the sapling (intenseand asymmetric) to the tree (weak and symmetric or almost absent). In conclusion (1) asymmetric and intense competition betweensaplings brought about habitat segregation between the dominantspecies,Picea jezoensisandAbies sachalinensis, in the earlystage of life-history; (2) therefore, the coexistence ofPiceajezoensisandAbies sachalinensisof the sub-boreal forest wasdetermined by the boundary conditions for the growth dynamicsof the trees, as segregation of establishment sites resultingfrom asymmetric and intense competition between saplings; (3)then the species composition of the forest was maintained byweak symmetric competition or the almost absence of competitionbetween trees. Crown shape; growth dynamics; species coexistence; habitat segregation; diffusion model     

Clonal integration affects growth, photosynthetic efficiency and biomass allocation, but not the competitive ability, of the alien invasive Alternanthera philoxeroides under severe stress

Background and Aims: Many notorious alien invasive plants are clonal, but littleis known about some roles and aspects of clonal integration.Here, the hypothesis is tested that clonal integration affectsgrowth, photosynthetic efficiency, biomass allocation and competitiveability of the exotic invasive weed Alternanthera philoxeroides(Amaranthaceae). Methods: The apical parts of Alternanthera were grown either with orwithout the lawn grass Schedonorus phoenix (tall fescue) andtheir stolon connections to the basal parts grown without competitorswere either severed or left intact. Key Results: Competition greatly reduced the maximum quantum yield of photosystemII (F_v/F_m) and growth (biomass, number of ramets and leaves,total stolon length and total leaf area) of the apical Alternanthera,but not the biomass of S. phoenix. Stolon connections significantlyincreased F_v/F_m and growth of Alternanthera. However, such effectson growth were smaller with than without competition and stolonconnections did not alter the relative neighbour effect of Alternanthera.Stolon connections increased Alternanthera's biomass allocationto roots without competition, but decreased it with competition. Conclusions: Clonal integration contributed little to Alternanthera's competitiveability, but was very important for Alternanthera to exploreopen space. The results suggest that the invasiveness of Alternantheramay be closely related to clonal integration.     

Biogeographic and Ecological Forces Responsible for Speciation in Ateles

We used the results of phylogenetic analyses of relationships among spider monkeys (Ateles) based on mitochondrial and nuclear DNA to investigate questions of their evolutionary origins and speciation mechanisms. We employed the concept of a local molecular clock to date nodes of interest (corresponding to hypothesized species and subspecies) in the various phylograms for comparison to hypothesized biogeographical events that might have affected speciation. We considered various mechanisms—Pleistocene refuge formation, riverine barriers, geological fluctuations, and ecological changes associated with these mechanisms—for their contribution to speciation in Ateles. Most speciation among the various species of Ateles occurred during the middle to late Pliocene, suggesting that Pleistocene refuge formation was not a key speciation mechanism. However, it is likely that the genetic structure of populations of Ateles was modified to some extent by refuge formation. Additionally, riverine barriers do not seem to interrupt gene flow significantly among Ateles. No river formed a barrier among species of Ateles, with the exception of the lower Amazon and possibly some of the black-water rivers draining the Guianan highlands. Large-scale geographic changes associated with the continued rise of the eastern and western cordilleras of the northern Andes and associated changes in habitat were the most important causes of speciation in Ateles. The various factors that modify genetic structure in Ateles are important to consider in order to protect endangered primate genera in the Neotropics.     

OBSERVATIONS ON SHELL MORPHOLOGY, ENZYMES AND RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) IN BULINUS AFRICANUS GROUP SNAILS (GASTROPODA: PLANORBIDAE) IN ZANZIBAR

The taxonomic status of Bulinus globosus and B. nasutus as separatespecies remains unclear, espécially in areas of EastAfrica where their distribution overlaps. In order to throwfurther light on this question, a study was carried out on snailscollected from the islands Unguja and Pemba, collectively knownas Zanzibar, which lie in the Indian Ocean close to mainlandAfrica. In total, 169 snails from 22 sample sites were characterisedby three methods: morphometric analysis of 15 shell measurements,enzyme analysis involving three enzyme systems and analysiswith random amplified polymorphic DNA (RAPD). Enzyme analysesindicated that both B. nasutus and B. globosus were presenton each island and their distribution was allopatric. Shellvariation was considerable but did not clearly differentiatethese taxa. Similarly, RAPD analysis indicated substantial geneticvariation with in and between samples; more often than not,no two RAPD profiles were identical within the sample. On Pemba,B. globosus is more widely dispersed than B. nasutus which isconfined to the eastern coast of the central region. On Unguja,B. globosus is found in more northern areas than B. nasutus. (Received 15 August 1996; accepted 31 January 1997)     

Electrotonic Transmission of an Action Potential between Two Separated Internodal Cells of Chara through a Bridge

Two separated internodal cells of Chara braunii were broughtinto contact with each other longitudinally at their ends andconnected by another pathway composed of a metal bridge beyondthe region of intercellular contact. A conducted action potentialthat arrived at one foot of the bridge electrotonically depolarizedthe other foot of the bridge in the connected cell. The electriccoupling ratio (0.07?0.03), the ratio of the change in the membranepotential of one cell to that of the other cell, was too smallto allow transmission of an action potential. Two cells wereplaced in parallel and connected with two liquid bridges orpools, a' and b'. When the action potential of one cell wasconducted through one connecting pool (pool a)', the other cellwas depolarized electrotonically by the action current via theother connecting pool (pool b'). The coupling ratio was increasedto 0.26?0.07 by the solution bridge, but transmission of theaction potential was rarely observed. Application of 1 mM KC1to pools a' and/or b' slightly improved the frequency of transmissionof the action potential. When pool b' contained 5% urethane,the coupling ratio increased to 0.31?0.08 and transmission ofthe action potential was frequent. (Received August 24, 1989; Accepted March 14, 1990)     

Zooplankton prey selection by juvenile fish in Nova Scotian Shelf basins

The stomach contents of fish <100 mm standard length (SL)and fish >100 mm SL collected during June and October intwo deep basins on the Scotian Shelf, showed that juvenile co(and silver hake fed primarily on the two most abundant speciesof zooplankton in the basins: Calanus finmarchicus and Meganyctiphanesnorvegica. These zooplankton were abundant in the basin: duringthe 2 months, forming high concentrations at depths below 200m during the day. In June fish (<100 mm SL) concentratedin the upper 50 m during both day and night. Cod and wolffislcollected between 195 and 240 m had a large percentage of C.finmarchicusin their stomachs suggesting that these fish exploited the highconcentrations of C.finmarchicus below 200 m depth There wasno evidence that Calanus hyperboreus was eaten by any juvenilefish species. Calanus finmarchicus was the most common preyof cod feeding in the top 50 m, but the percentages o C.finmarchicusstages IV and V were lower in the stomachs than in the watercolumn. Cod showed ; strong preference for M.norvegica, withthis prey species having a modified Ivlev's index of 1 indicatingthat cod were highly selective for this species. There was noevidence that C.hyperboreus. stage IV was eaten by any of thespecies offish. Silver hake and dogfish (>100 mm SL) bothfeed oi M.norvegica and C.finmarchicus in the deep regions ofthe basins. In October, silver hake was the most common juvenilefish in the basins, feeding primarily on small stages of M.norvegica.The populations of fish (>100 mm SL) in the basins were mainlyspecies known to feed heavily or euphausiids. The two basinsare unique regions of the shelf because of the large populationsof Calanus copepods and M.norvegica they contain all the yeararound, thereby providing an atrractive feeding ground for manyspecies of fish, particularly silver hake.     

Predicted Patterns of Photosynthetic Production in Maritime Antarctic Mosses

The microclimate of a moss turf of Polytrichum alpestre Hoppeand a moss carpet of Drepanocladus uncinatus (Hedw.) Warnst.is described for two sites in the maritime Antarctic. Thesemicro-climatic data, together with some additional data, arethen used in the solution of multiple regression equations describingnet photosynthetic response to variation in radiant flux densityand temperature as measured in Antarctic material of the twomosses grown under controlled conditions in the U.K. Predictionsare made of daily and seasonal courses of net photosynthesisat the Antarctic field site. The basis of acclimation of netphotosynthesis to growth temperatures through a season is discussedand the physiological basis of growth under snow is examined. Polytrichum alpestre. Hoppe, Drepanocladus uncinatus (Hedw.) Warnst., mosses, Bryophyta photosynthesis, productivity, Antarctic     

Fossil Ponderosa-like Pine Wood from the Upper Cretaceous of North-east Mississippi

Petrified wood from the Lower Upper Cretaceous of north-easternMississippi (Eutaw Formation) in thin-section is most similarto extant Pinus woods of section Pinus, subsection Ponderosae.However, several features also suggest woods of subsection Australes.Based on anatomical detail, geologic age and geographic position,this fossil may represent an ancestral connection between thetwo subsections. Pinuxylon eutawense, silicified wood, Cretaceous, Mississippi, Pinus ponderosa, Pinus taeda     

Impact of weather conditions,seasonality and moonlight on the use of artificial canopy bridges by nocturnal arboreal mammals

Natural and artificial canopy bridges can be used to mitigate the effects of habitat fragmentation. Understanding the ecological factors that influence bridge use is imperative to the effective design and placement of this potential conservation intervention. Moonlight, seasonality and weather may influence the cost and risk of using bridges, potentially reducing their effectiveness. We installed five artificial waterline bridges and, between 2017 and 2019, monitored via camera trapping their use by Javan palm civets Paradoxurus musanga javanicus and Javan slow lorises Nycticebus javanicus. We used a weather station to record microclimate data (temperature and relative humidity) and calculated the illumination percentage of the moon. We tested the influence of moon luminosity, relative humidity, seasonality (Julian day) and temperature on the frequency of bridge use via Generalised Additive Models. Camera traps captured 938 instances of bridge use by civets, which was significantly lower than the reference value at moon luminosity?>?90%, temperatures?>?20 °C, humidity?>?90%, and during the drier period (May–July). Camera traps captured 1036 instances of bridge use by lorises, which was significantly lower than the reference value during the drier period and higher than the reference value at temperatures?>?20 °C. Lorises showed peaks in bridge use close to sunset and sunrise whereas civets showed peaks around 2 h after sunset and 2 h before sunrise. Our study illustrates the utility of simple-to-construct bridges by two sympatric nocturnal mammals facing severe habitat loss, with bridge use differing between those species according to abiotic factors. In particular, less use by both taxa during the drier season could suggest modifying placement of bridges or providing another intervention during that time. Camera traps were an excellent mechanism to record these differences and to validate the importance of the bridges, including during inclement weather and dark nights, when observations would be more difficult for human observers. By understanding the influence that abiotic factors have on the use of artificial bridges, we can improve bridge placement and construction to encourage use by a variety of species, particularly those threatened by habitat fragmentation.

     

Overwintering habitat selection by the mummichog, Fundulus Heteroclitus, in a Cape Cod (USA) salt marsh

This study tracked the seasonal distribution and winter habitat selection of the mummichog, Fundulus heteroclitus (Linnaeus), in a Cape Cod, Massachusetts salt marsh. Fish (mean size = 43.1 mm total length, range = 10–93 mm) were collected with a 1 m² throw trap and by excavating sediments. In fall, F. heteroclitus began migrating upstream in creeks and eventually moved into upstream pools where they remained throughout winter. F. heteroclitus burrowed into the sediments of these pools at a density of 0.5 fish m^–2, but was not found burrowed in the sediments of downstream pools or any creeks. Sediments in upstream pools were composed of a higher proportion of fine-grained particles and organic content than other marsh pools and creeks, and winter temperatures in upstream pool sediments remained above 1 °C. Temperatures in the water column and sediments of downstream pools regularly dropped below –1.8 °C, exceeding the lethal limit for F. heteroclitus. These results support other recent work showing that F. heteroclitus migrates upstream in salt marshes in fall and overwinters in salt marsh pools. Moreover, this study demonstrates that F. heteroclitus does not utilize all available pools as overwintering habitat but apparently selects pools with sediments that offer a thermal refuge from lethal winter temperatures.     

不同地区甜菜夜蛾种群的遗传多样性分析

甜菜夜蛾Spodoptera exigua (Hübner)是一种重要的农业害虫,曾给我国农牧业生产造成过重大的经济损失。为了阐明甜菜夜蛾的种群动态规律,改善和提高其预测、防治水平,我们应用扩增片段长度多态性(AFLP)技术对我国7个甜菜夜蛾种群的42头雄蛾的遗传多样性进行了研究分析。结果表明,不同种群个体间遗传相似性指数分布在0.143～0.824之间,同一种群内不同个体间的遗传相似性指数分布在0.250～0.786之间,同一种群内个体间的遗传相似性指数有许多小于不同种群个体间的。江西种群的多态性条带比例最低,为80.7%; 山东种群的多态性条带比例最高,达88.6%。总体而言,北方种群内的遗传多样性高于南方种群。聚类分析结果表明,同一种群的个体并不总能聚在一起,即种群间不存在明显的遗传分化。这些结果为明确我国甜菜夜蛾的迁飞规律及各发生危害区的虫源关系提供了进一步的实验依据。     

A Taxonomic Study of Brassica juncea using the Techniques of Electrophoresis, Gas-liquid Chromatography and Serology

A previous investigation of volatile isothiocyanates had producedevidence for the existence of two geographic races of Brassicajuncea. The present paper records a reinvestigation of the taxonomyof B. juncea but, on this occasion, volatile oil distributionhas been recorded by means of gas-liquid chromatography. Inaddition, seed proteins have been compared by means of electrophoreticand serological techniques. The bearing of the biochemical informationupon the taxonomy of the species is discussed.     

Seasonal dynamics of Skistodiaptomus pallidus Herrick and other zooplankton populations in Deer Lake, S.W. British Columbia

Seasonal environmental conditions and dynamics of a Skistodiaptomuspallidus population are given for a 2-year period in eutrophicDeer Lake, an urban waterbody near the northern limit of thiscalanoid's distribution. Life history characteristics of S.pallidus in the lake appear similar to those in more southerlyhabitats. It was perennial with breeding occurring between Marchand November; there were probably five generations producedper year. The annual cycles of Daphnia rosea, D. pulicaria.Diacyclops bicuspidatus thomasi, Bosmina longirostris, rotifersand Chaoborus flavicans are briefly described.     

Some Thermal Requirements of Fiddler Crabs of the Temperate and Tropical Zones and Their Influence on Geographic Distribution

Thermal stress is one environmental parameter that has greatlyinfluenced the migration of crustaceans from the sea to land.Since a greater number of species of terrestrial crabs are foundin the tropics than in the temperate zone, comparative studiesof the influence of temperature on latitudinally separated populationswere undertaken. Two tropical species, U. rapax and U. thayeri,may occur as far north as St. Augustine, Florida, or, followinga severe winter, may be rare north of Cape Kennedy. The lethaleffect of the low temperatures recorded during one severe winter(1957–58) is supported by laboratory studies in whichLD₅₀, deaths occurred in 4.5 days at 10°C for U. rapax acclimatedto 18°C. The experiment demonstrates that U. rapax cannotacclimate to and survive low temperatures. This contrasts markedlywith the situation in semi-terrestrial crabs of the temperatezone, which are able to acclimate to cold. The distribution of Uca around Cape Cod Bay correlates wellwith the coastal hydrographic thermal gradient and supportsPassano's suggestion that temperatures below 20° may belimiting as they inhibit proecdysis in U. pugnax. Such an inhibitionis found experimentally in U. pugilator and in the tropicalspecies, U. rapax. It is hypothesized that a shift in the thermodynamicsof the processes underlying molting has not occurred in Ucaof the temperate zone. The paucity of semi-terrestrial Brachyurain the temperate zone may be due to the failure of many speciesto evolve capacity-adaptations to carry out all requisite lifeprocesses at temperatures below 20°, or the resistance-adaptationsnecessary to survive the low temperatures of winter.