Spring Populations Research Articles

Ecological differentiation in planktonic and sediment-associated chemotropic microbial populations in Yellowstone hot springs.

National Aeronautics and Space Administration Exobiology and Evolutionary Biology (NNX13AI11G); National Science Foundation (EAR-1529963)

Insights into the migration of the European Roller from ring recoveries

Despite recent advances in avian tracking technology, archival devices still present several limitations. Traditional ring recoveries provide a complementary method for studying migratory movements, particularly for cohorts of birds with a low return rate to the breeding site. Here we provide the first international analysis of ring recovery data in the European Roller Coracias garrulus, a long-distance migrant of conservation concern. Our data comprise 58 records of Rollers ringed during the breeding season and recovered during the non-breeding season. Most records come from Eastern Europe, half are of juveniles and over three quarters are of dead birds. Thus, ring recoveries provide migration data for cohorts of Rollers—juveniles and unsuccessful migrants—for which no information currently exists, complementing recent tracking studies. Qualitatively, our results are consistent with direct tracking studies, illustrating a broad-front migration across the Mediterranean Basin in autumn and the use of the Arabian Peninsula by Rollers from eastern populations in spring. Autumn movements were, on average, in a more southerly direction for juveniles than adults, which were more easterly. Juvenile autumn recovery direction also appeared to be more variable than in adults, though this difference was not statistically significant. This is consistent with juveniles following a naïve vector-based orientation program, and perhaps explains the ‘moderate’ migratory connectivity previously described for the Roller. In the first (qualitative) analysis of Roller non-breeding season mortality, we highlight the high prevalence of shooting. The recovery age ratio was juvenile-biased in autumn but adult-biased in spring. Although not statistically significant, this difference points towards a higher non-breeding season mortality of juveniles than adults. Our study demonstrates the complementarity of ring recoveries to direct tracking, providing an insight into the migration of juvenile Rollers and non-breeding season mortality.

Effects of Wintering Environment and Parasite-Pathogen Interactions on Honey Bee Colony Loss in North Temperate Regions.

Extreme winter losses of honey bee colonies are a major threat to beekeeping but the combinations of factors underlying colony loss remain debatable. We monitored colonies in two environments (colonies wintered indoors or outdoors) and characterized the effects of two parasitic mites, seven viruses, and Nosema on honey bee colony mortality and population loss over winter. Samples were collected from two locations within hives in fall, mid-winter and spring of 2009/2010. Although fall parasite and pathogen loads were similar in outdoor and indoor-wintered colonies, the outdoor-wintered colonies had greater relative reductions in bee population score over winter. Seasonal patterns in deformed wing virus (DWV), black queen cell virus (BQCV), and Nosema level also differed with the wintering environment. DWV and Nosema levels decreased over winter for indoor-wintered colonies but BQCV did not. Both BQCV and Nosema concentration increased over winter in outdoor-wintered colonies. The mean abundance of Varroa decreased and concentration of Sacbrood virus (SBV), Kashmir bee virus (KBV), and Chronic bee paralysis virus (CBPV) increased over winter but seasonal patterns were not affected by wintering method. For most viruses, either entrance or brood area samples were reasonable predictors of colony virus load but there were significant season*sample location interactions for Nosema and BQCV, indicating that care must be taken when selecting samples from a single location. For Nosema spp., the fall entrance samples were better predictors of future infestation levels than were fall brood area samples. For indoor-wintered colonies, Israeli acute paralysis virus IAPV concentration was negatively correlated with spring population size. For outdoor-wintered hives, spring Varroa abundance and DWV concentration were positively correlated with bee loss and negatively correlated with spring population size. Multivariate analyses for fall collected samples indicated higher DWV was associated with colony death as did high SBV for spring-collected samples.

Ecological differentiation in planktonic and sediment-associated chemotrophic microbial populations in Yellowstone hot springs

Chemosynthetic sediment and planktonic community composition and sizes, aqueous geochemistry and sediment mineralogy were determined in 15 non-photosynthetic hot springs in Yellowstone National Park (YNP). These data were used to evaluate the hypothesis that differences in the availability of dissolved or mineral substrates in the bulk fluids or sediments within springs coincides with ecologically differentiated microbial communities and their populations. Planktonic and sediment-associated communities exhibited differing ecological characteristics including community sizes, evenness and richness. pH and temperature influenced microbial community composition among springs, but within-spring partitioning of taxa into sediment or planktonic communities was widespread, statistically supported (P < 0.05) and could be best explained by the inferred metabolic strategies of the partitioned taxa. Microaerophilic genera of the Aquificales predominated in many of the planktonic communities. In contrast, taxa capable of mineral-based metabolism such as S(o) oxidation/reduction or Fe-oxide reduction predominated in sediment communities. These results indicate that ecological differentiation within thermal spring habitats is common across a range of spring geochemistry and is influenced by the availability of dissolved nutrients and minerals that can be used in metabolism.

Morphological variations of wild populations of Nile tilapia (Oreochromis niloticus) living in extreme environmental conditions in the Kenyan Rift-Valley

In this study, we use geometric morphometric method to establish morphological differences between natural populations of Nile tilapia from two extreme environmental conditions (high temperature and salinity) in Kenya, and compare them to two populations from regions experiencing less extreme conditions. To determine genetic influence on morphology, we correlated genetic data with morphological data. The study observed significant morphological differences between all studied populations, including three closely related hot spring populations (Bogoria, Chelaba and Turtle Springs), and two populations with similar genetic background inhabiting saline environments in Lake Turkana basin (Turkana and Crocodile Lake populations). In addition, allometric growth patterns of the seven populations differed significantly, demonstrating that developmental changes (plastic or adaptive) operated between these populations. Positive correlation between morphometric and genetic data confirmed the influence of genetic factors on morphology. All observed differences were attributed either to genetic and/or environmental factors, which seemed to play a major role in influencing morphology of wild Nile tilapia populations. We recommend further studies to be carried out under controlled conditions to confirm the role of temperature, pH and salinity in morphological diversification of Nile tilapia.

Trophic plasticity among spring vs. cave populations of Gammarus minus: examining functional niches using stable isotopes and C/N ratios

AbstractIn some environments, species may exhibit trophic plasticity, which allows them to extend beyond their assigned functional group. For Gammarus minus, a freshwater amphipod classified as a shredder or detritivore, cave populations have been observed consuming heterotrophs as well as shredding leaves, and therefore may be exhibiting trophic plasticity. To test this possibility, we examined the C and N stable isotope and C/N ratios for cave and spring populations of G. minus. A 15‐day feeding experiment using leaves and G. minus from a spring population established that the diet‐tissue discrimination factor was 3.2 ‰ for δ15N. Cave G. minus were 8 ‰ higher in δ15N relative to cave leaves, indicating they did not derive nitrogen from leaves, whereas field collected spring populations were 2–3 ‰ higher than spring leaves, indicating that they did. Cave G. minus were 2.6 ‰ higher in δ15N than the cave isopod, Caecidotea holsingeri. Relative to spring populations, Organ Cave G. minus were 15N enriched by 6 ‰, suggesting they occupied a different trophic level, or incorporated an isotopically distinct N source. While stable isotopes cannot tell what the cave G. minus are eating, the isotopes certainly show that G. minus are not eating leaves and are trophically distinct form the surface populations. Differences in C/N ratios were observed, but reflect the size of the G. minus examined and not feeding group or habitat. The isotope data strongly support the hypothesis that cave populations of G. minus have become generalist or omnivorous by including animal protein in their diet.

Mechanisms Underlying Adaptation to Life in Hydrogen Sulfide-Rich Environments.

Hydrogen sulfide (H2S) is a potent toxicant interfering with oxidative phosphorylation in mitochondria and creating extreme environmental conditions in aquatic ecosystems. The mechanistic basis of adaptation to perpetual exposure to H2S remains poorly understood. We investigated evolutionarily independent lineages of livebearing fishes that have colonized and adapted to springs rich in H2S and compared their genome-wide gene expression patterns with closely related lineages from adjacent, nonsulfidic streams. Significant differences in gene expression were uncovered between all sulfidic and nonsulfidic population pairs. Variation in the number of differentially expressed genes among population pairs corresponded to differences in divergence times and rates of gene flow, which is consistent with neutral drift driving a substantial portion of gene expression variation among populations. Accordingly, there was little evidence for convergent evolution shaping large-scale gene expression patterns among independent sulfide spring populations. Nonetheless, we identified a small number of genes that was consistently differentially expressed in the same direction in all sulfidic and nonsulfidic population pairs. Functional annotation of shared differentially expressed genes indicated upregulation of genes associated with enzymatic H2S detoxification and transport of oxidized sulfur species, oxidative phosphorylation, energy metabolism, and pathways involved in responses to oxidative stress. Overall, our results suggest that modification of processes associated with H2S detoxification and toxicity likely complement each other to mediate elevated H2S tolerance in sulfide spring fishes. Our analyses allow for the development of novel hypotheses about biochemical and physiological mechanisms of adaptation to extreme environments.

Searching for Radical Solutions against Fouling Communities Inhabiting the Arabian Gulf in Saudi Arabia

Searching for Radical Solutions against Fouling Communities Inhabiting the Arabian Gulf in Saudi Arabia Sea squirts produce pelagic larvae that spend few days in the plankton before settling and metamorphosing into their adult sessile forms. Attachment mechanism developed usually relies on highly viscous or solid adhesive secretions, which all contain specialized proteins and glycogen. Adult sea squirts of Ciona intestinalis, Molgula manhattensis, Ascidella aspersa and Phallusia nigra were sampled for 12 months from three estuarine localities of the Arabian Gulf (Ad-Dammam; Northern Khobar and Southern Khobar). Seasonal variation of some analyzed abiotic factors revealed that the population densities of ascidians and the feasibility of larval dispersal were variable not only according to seasons but also according to the study locality where ascidians predominate Southern Khobar˃Northern Khobar ≈ Ad-Dammam and during spring and summer populations are ˃˃ those of autumn < those of winter. Procurement of gametes has been carried out by potassium chloride injection or/and artificial heterologous fertilization. Larvae were cultured and three larval stages were identified. Immunocytochemical approach has been applied to investigate larval metamorphosis under the influence of applied bioactive inducers which had been claimed to induce metamorphosis or involved in signaling systems or serve as neurotransmitters or control morphogenetic and behavioral reactions or interact with members of several signal transduction proteins pathways. The transformation of the larval stage with long tail to the next larval stage with remarkable tail resorption activity is accelerated by NH4Cl 2.5 mM, C8 1 μM, Acetyl choline 1 mM, NOS 1 mM and cGMP 1 μM. To investigate whether NO and HSP 90 play a role in larval metamorphosis, larvae with long tail, partially metamorphosed larvae with short tail and metamorphosing youngs were treated for whole-mount immunohistochemistry towards the green fluorescent protein (GFP). High-pressure chromatographic separation has been carried out to identify amino acids in the adhesive secretions of the larval stage. Western blotting routine technique (Immune blotting) using Bradford assay has been applied to identify proteins of adhesives. SDS-PAGE revealed that the adhesives contained about 11 different proteins. Their apparent molecular masses were approximately 300, 280, 250, 150, 100, 75, 50, 35, 25, 20, and 10 kDa. Total lipids were extracted using capillary gas chromatography and total carbohydrates of adhesives were analyzed by the Phenolsulphuric acid method. This study concluded that lipids of adhesives is secreted first and represented by C14:0; C18:2 V-32; C20:1 V-9; C18:1 V-7; C16:1 V-6 and C18:1 V-5. A post-translational modification of amino acids mainly Phenylalanine, Methionine Threonine, Valine and Serine with glycogen for adhesive and cohesive function occurs. The carbohydrate moiety of adhesives is a polymerization of monosaccharides. All data obtained were subjected to analysis of variance (ANOVA) means significant difference P>0.05 or P<0.05, column comparison test P<0.0001; Df 51-207 and Tukey post hoc test. Bartlett’s test for equal variances P value 0, 4095 has been applied. This study suggested that a fine powdery copper catalyst or boric acid esters and Didecyl polyoxyethyl ammonium borate (DPAB) have to be added as antifouling agents to the paint materials of ships, boats and steels objects in the Arabian Gulf to minimize or prevent fouling stress.

Investigating dormant-season application of pheromone in citrus to control overwintering and spring populations of Phyllocnistis citrella (Lepidoptera: Gracillariidae).

The leafminer, Phyllocnistis citrella Stainton, reproduces on leaf flush during winter. Deployment of pheromone during winter could suppress moth populations in spring and summer more than a spring application alone. We tested the primary pheromone component of P. citrella, (Z,Z,E)-7,11,13-hexadecatrienal, released gradually over several months from elastomeric dispensers in a citrus grove in 6.4 ha main plots in winter and/or 3.2 ha subplots in spring (834 mg triene ha(-1) ) and evaluated moth catch and leaf mining. After winter treatment, dispensers provided >85% disruption of male moth catch in traps for 37 weeks, and after spring treatment they provided >92% disruption for 26 weeks, but there was only a 12% reduction in leaf infestation in spring. Two applications were no better than only a single application in spring. Disruption of moth catch was weaker in treated plots where traps were placed high (3.1 m) rather than low (1.6 m) in the tree canopy. Dispensers provided effective and persistent disruption of male catch in pheromone-baited monitoring traps but were minimally effective in reducing leaf infestation by P. citrella. Winter application of pheromone did not reduce leaf mining in spring compared with spring application alone. Tops of trees may have provided a refuge for mating. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Reproductive characteristics of invasive hyperparasitoid Baeoanusia albifunicle have implications for the biological control of eucalypt pest Paropsis charybdis

Hyperparasitoids can impede the establishment of primary parasitoid biological control agents or limit their control capacity. Although modern quarantine practices generally prevent hyperparasitoids being introduced with biological control agents, introductions can occur via natural pathways or accidentally with incoming passengers and cargo. In New Zealand, Baeoanusia albifunicle Girault is a self-introduced hyperparasitoid of Enoggera nassaui Girault, an intentionally introduced control agent of the eucalypt pest Paropsis charybdis Stål. A self-introduced primary parasitoid, Neopolycystus insectifurax (Girault), also parasitises P. charybdis in New Zealand. We assessed B. albifunicle biology to better understand its potential to disrupt P. charybdis control. It was determined that B. albifunicle is an obligate solitary hyperparasitoid with a longer lifespan, lower fecundity and longer generation time than its host. The hyperparasitoid reduced effective parasitism by E. nassaui to <10% in the lab, indicating it may limit control of the first P. charybdis generation by slowing spring population growth. It was confirmed that N. insectifurax is not hyperparasitised by B. albifunicle and therefore has some potential to substitute for any hyperparasitoid-driven decline in E. nassaui.

Functional gene diversity and migration timing in reintroduced Chinook salmon

Reintroductions are used to reestablish populations to historical habitats from which they were extirpated. The long-term success of these efforts will depend on genetic diversity and the ability of reintroduced individuals to adapt to ecological change. We examined variation at circadian clock (OtsClock1b and OmyFbxw11) and reproductive timing (Ots515NWFSC)—associated genes in two threatened spring-run Chinook salmon (Oncorhynchus tshawytscha) populations that are undergoing restoration to historical habitats above dams. We also tested for an association between the genes and individual variation in arrival time to the spawning grounds. Our findings indicate that levels of genetic diversity in reintroduced individuals are similar to those found in previously studied spring, summer, fall and winter-run Chinook salmon populations. Captive-rearing programs established following dam construction and the more recent reintroduction efforts thus appear to have maintained diversity at these genes. We observed temporal (between run-years) and spatial (between populations) patterns of genetic differentiation, but little evidence that selection underlies these differences. However, there was a relationship between the circadian-associated gene, OmyFbxw11, and arrival time to the spawning grounds, and in one year of the study, “early” and “late” arrivers to the spawning grounds were more differentiated at the gene than at neutral markers. Taken together, these findings suggest that reintroduced salmon may be capable of an evolutionary response to ecological shifts that alter the adaptive landscape between fitness and arrival timing to the spawning grounds.

Cold Regime interannual variability of primary and secondary producer community composition in the southeastern Bering Sea.

Variability of hydrographic conditions and primary and secondary productivity between cold and warm climatic regimes in the Bering Sea has been the subject of much study in recent years, while interannual variability within a single regime and across multiple trophic levels has been less well-documented. Measurements from an instrumented mooring on the southeastern shelf of the Bering Sea were analyzed for the spring-to-summer transitions within the cold regime years of 2009–2012 to investigate the interannual variability of hydrographic conditions, primary producer biomass, and acoustically-derived secondary producer and consumer abundance and community structure. Hydrographic conditions in 2012 were significantly different than in 2009, 2010, and 2011, driven largely by increased ice extent and thickness, later ice retreat, and earlier stratification of the water column. Primary producer biomass was more tightly coupled to hydrographic conditions in 2012 than in 2009 or 2011, and shallow and mid-column phytoplankton blooms tended to occur independent of one another. There was a high degree of variability in the relationships between different classes of secondary producers and hydrographic conditions, evidence of significant intra-consumer interactions, and trade-offs between different consumer size classes in each year. Phytoplankton blooms stimulated different populations of secondary producers in each year, and summer consumer populations appeared to determine dominant populations in the subsequent spring. Overall, primary producers and secondary producers were more tightly coupled to each other and to hydrographic conditions in the coldest year compared to the warmer years. The highly variable nature of the interactions between the atmospherically-driven hydrographic environment, primary and secondary producers, and within food webs underscores the need to revisit how climatic regimes within the Bering Sea are defined and predicted to function given changing climate scenarios.

Effects of Water Chemistry on the Life History of the Least KillifishHeterandria formosaand the Absence of Evidence for Local Adaptation

This study explored whether persistent differences in life history traits between populations of Least Killifish Heterandria formosa could be explained by differences in habitat-associated water type, reflecting either local adaptation or phenotypic plasticity. Fish native to a pond and a spring site were reared in the lab in either pond or spring water. Fish reared in pond water reached maturity faster and at the same size as fish reared in spring water, regardless of source population. There was no difference in daily mortality rate between fish raised in the different water types, but the longer time to maturity in spring water produced a lower cumulative survival to maturity. Water type did not affect fecundity, but fish from the spring population had larger offspring, contrary to patterns found in both the field and previously in the lab. Persistent differences among natural populations in life history traits have previously been attributed to differences in population density and predation pressure....

紫外辐射对菹草成株表型可塑性及石芽的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 紫外辐射对菹草成株表型可塑性及石芽的影响 DOI: 10.5846/stxb201401160120 作者: 作者单位: 南京信息工程大学应用气象学院,南京信息工程大学环境科学与工程学院,南京信息工程大学大气物理学院,江苏省大气环境监测与污染控制高技术重点实验室;南京信息工程大学环境科学与工程学院,南京信息工程大学应用气象学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41105113,51109109);江苏省环境演变与生态建设重点实验室开放基金资助项目;南京信息工程大学本科生优秀毕业论文(设计)支持计划项目 Effect of ultraviolet radiation on phenotypic plasticity and turion of Potamogeton crispus Author: Affiliation: School of Applied Meteorology, Nanjing University of Information Science & Technology,School of Environmental Science and Engineering,Nanjing University of Information Science Technology,School of Atmospheric Physics, Nanjing University of Information Science & Technology,Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control;School of Environmental Science and Engineering,Nanjing University of Information Science Technology,Nanjing University of Information Science Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:菹草衰亡的原因一直是水体生态修复的研究热点,已有的研究认为强光照是促进菹草衰亡的关键因素,强光照中对动植物有害波段主要为UV-B波段,为此分别将菹草成株置于50、100、150、200 μW/cm2剂量的UV-B辐射下,每日持续辐射6h(9:00-15:00),对照组接受的UV-B剂量为0,仅接受UV-A和光合有效辐射,监测菹草生长、形态状况、石芽形成及萌发等指标。结果表明,高剂量UV-B辐射能促进菹草成株的衰亡进程,即使暴露在低剂量UV-B辐射条件下,植株仍然衰亡;植株株高、节间距、叶面积、单株鲜重都受到UV-B辐射的抑制,且随UV-B辐射剂量增加,各项指标明显下降;UV-B辐射对菹草成株形成的石芽数量无显著影响,但形成的石芽随辐射剂量增加变态率增高,长度增加,宽度减少,石芽重量减轻,下一个生长季萌发率降低,萌发出二苗的比率降低,萌发苗各项生长指标随辐射剂量增加逐渐降低。因此,春末夏初UV-B辐射增强可能是导致菹草大批衰亡的重要原因。 Abstract:Potamogeton crispus is important in purifying water and maintaining a healthy aquatic ecosystems such as shallow lakes. However, mass mortality occurs in P. crispus populations in the late spring and early summer, which possibly results in secondary pollution. Therefore, the causes of P. crispus mass mortality have been a very important research topic in the field of water ecological restoration. The UV-B band in the strong light is generally recognized to damage plants and animals and even to penetrate into the water column and harm aquatic organisms. Some researchers have reported that intense light is the key factor in P. crispus decline. We carried out a series of experiments to find the effect of UV-B radiation in the strong light on P. crispus decline. In this study, adult plants of P. crispus are exposed to UV-B radiation in different doses (50 μW/cm2, 100 μW/cm2, 150 μW/cm2, and 200 μW/cm2) for 6 hours (9:00-15:00) every day, and the control group was exposed only to UV-A radiation and photosynthetically active radiation (PAR). Plant growth, morphological changes (plant height, internodal length, leaf area and fresh weight), turion formation (number, weight, and morphology of turion) and the germination indexes of turion were monitored. The results show that UV-B radiation can accelerate plant decline. When the exposure dose is in excess of 150 μW/cm2, the plants decline and fall within 31 days, while a few plants in the other treatment groups still grow. The tops of the plants are damaged more when they receive higher doses of UV-B radiation, so that plant height declines persistently with UV-B radiation, the internodal length is shortened by UV-B radiation, the leaf area shrinks, and the average fresh weight per plant decreases; whereas the plant height and internodal length of the control group increase till the 24th day, the leaf area also increases till the 16th day, and the average fresh weight per plant decreases gradually with increasing radiation doses. UV-B radiation had no effect on turion quantity in both the treatment and control groups, but the metamorphosis ratio of turion increases with the increasing radiation dose. When the exposure dose of UV-B radiation increases, the turion length increases, whereas the turion width and weight are reduced, the germination rate from the next growing season is reduced. The ratio of two seedlings that germinated from these turions decreases and the seedling growth indexes (germination rate, plant height, leaf number, leaf length, leaf width, leaf area, and so on) decrease and are significantly reduced especially when the exposure dose is in excess of 150 μW/cm2. The results indicate that UV-B radiation may be an important factor leading to mass mortality of P. crispus in late spring and early summer. Accordingly, we deduce that the sharply enhanced ultraviolet radiation on the land surface in the late spring and early summer leads to mass mortality of the natural P. crispus population. However, further research is necessary to study whether UV-B radiation acts synergistically with other environmental factors on the decline of P. crispus. 参考文献 相似文献 引证文献

Rapid rebound in colony number of an over‐hunted population of Eurasian beaver Castor fiber

The current reestablishment and growth of beaver Castor fiber populations throughout Eurasia has created a need for methods to control population size. While lethal‐trapping has been the most common harvest and control method for beaver world‐wide for centuries, in recent decades spring hunting has developed as the main lethal method in Norway, Sweden and Finland. An experimental hunt where hunters annually removed 22–26% (mean = 24%) of the estimated spring population of beavers on 242 km2 in southeast Norway led to an unanticipated 46% decline in colony number after only three years. We monitored the population response in colony number throughout the ensuing four years of no hunting during which time the number of colonies rebounded by 93%. The rapid increase in colony number suggested a high rate of dispersal to vacated colony sites by animals from unexploited colonies within the study area (approximately half were unexploited each year) and from bordering townships where harvest was light at the time. Increased fecundity usually follows in the wake of a significant reduction in the density of mammal populations and most likely contributed to the rapid rebound in colony number observed. We conclude that spring hunting can be employed to significantly reduce population size when desired and that over‐exploited populations may rebound quickly after hunting stops when dispersing individuals are in adequate supply from colonies both within and outside the harvested area.

An Important Natural Genetic Resource of Oreochromis niloticus (Linnaeus, 1758) Threatened by Aquaculture Activities in Loboi Drainage, Kenya

The need to improve food security in Africa through culture of tilapias has led to transfer of different species from their natural ranges causing negative impacts on wild fish genetic resources. Loboi swamp in Kenya is fed by three hot springs: Lake Bogoria Hotel, Chelaba and Turtle Springs, hosting natural populations of Oreochromis niloticus. The present study aimed at better genetic characterization of these threatened populations. Partial mtDNA sequences of the D-loop region and variations at 16 microsatellite loci were assessed in the three hot spring populations and compared with three other natural populations of O. niloticus in the region. Results obtained indicated that the hot spring populations had mitochondrial and nuclear genetic variability similar to or higher than the large closely related populations. This may be attributed to the perennial nature of the hot springs, which do not depend on rainfall but rather receive permanent water supply from deep aquifers. The study also revealed that gene flow between the three different hot spring populations was sufficiently low thus allowing their differentiation. This differentiation was unexpected considering the very close proximity of the springs to each other. It is possible that the swamp creates a barrier to free movement of fish from one spring to the other thereby diminishing gene flow. Finally, the most surprising and worrying results were that the three hot spring populations are introgressed by mtDNA genes of O. leucostictus, while microsatellite analysis suggested that some nuclear genes may also have crossed the species barrier. It is very likely that the recent intensification of aquaculture activities in the Loboi drainage may be responsible for these introgressions. Taking into account the importance of these new genetic resources, protection and management actions of the Loboi swamp should be accorded top priority to prevent the loss of these spring populations.

Combination of morphometric and isotopic tools for studying spring migration dynamics in Episyrphus balteatus

Migration and population dynamics are important in organisms that provide ecosystem services as they determine the occurrence of individuals in a given place at a given time, which, in turn, determines the efficiency of the service provided. To design appropriate landscape management strategies to improve the efficiency of biological control, it is essential to know the origin of beneficial insects that colonize agricultural fields. However, studying migration dynamics in insects is complicated by their small size and short life span which largely prevent the use of conventional techniques based on capture‐mark‐recapture, or remote sensing.Stable isotopes and morphological characters are intrinsic markers that can be used to infer the geographical origin of many organisms including insects. In this study, we first determined whether the hydrogen isotopic ratio and the wing morphometrics are appropriate markers to study the spring migration dynamics of a major aphidophagous hoverfly species (Episyrphus balteatus). To this end, we assessed the magnitude of variation of these indicators in seven populations along a north‐south gradient in Western Europe. Second, we used the two markers in E. balteatus individuals collected in a French agricultural landscape over the course of the spring to assess the proportion of immigrants from southern regions and the period of immigration.Our results revealed uncertainties associated with the use of the hydrogen isotopic ratio and wing morphometrics, but showed that the spring population of E. balteatus in Western France very likely comprises mainly local individuals, with the probable arrival of some immigrants from nearby regions located further south. The low proportion of immigrants in the spring population has important implications for the biological control provided by E. balteatus in terms of landscape management strategies.

Identification of the Key Weather Factors Affecting Overwintering Success of Apolygus lucorum Eggs in Dead Host Tree Branches

Understanding the effects of weather on insect population dynamics is crucial to simulate and forecast pest outbreaks, which is becoming increasingly important with the effects of climate change. The mirid bug Apolygus lucorum is an important pest on cotton, fruit trees and other crops in China, and primarily lays its eggs on dead parts of tree branches in the fall for subsequent overwintering. As such, the eggs that hatch the following spring are most strongly affected by ambient weather factors, rather than by host plant biology. In this study, we investigated the effects of three major weather factors: temperature, relative humidity and rainfall, on the hatching rate of A. lucorum eggs overwintering on dead branches of Chinese date tree (Ziziphus jujuba). Under laboratory conditions, rainfall (simulated via soaking) was necessary for the hatching of overwintering A. lucorum eggs. In the absence of rainfall (unsoaked branches), very few nymphs successfully emerged under any of the tested combinations of temperature and relative humidity. In contrast, following simulated rainfall, the hatching rate of the overwintering eggs increased dramatically. Hatching rate and developmental rate were positively correlated with relative humidity and temperature, respectively. Under field conditions, the abundance of nymphs derived from overwintering eggs was positively correlated with rainfall amount during the spring seasons of 2009–2013, while the same was not true for temperature and relative humidity. Overall, our findings indicate that rainfall is the most important factor affecting the hatching rate of overwintering A. lucorum eggs on dead plant parts and nymph population levels during the spring season. It provides the basic information for precisely forecasting the emergence of A. lucorum and subsequently timely managing its population in spring, which will make it possible to regional control of this insect pest widely occurring in multiple crops in summer.

English

The high altitude valley of Kashmir abounds in a vast array of freshwater bodies of lotic as well as lentic nature. Amongst these, lakes play an important role in biodiversity of this region. The present study on Wular Lake, Kashmir was undertaken from March, 2007 to February, 2008 to study abundance and distribution of phytoplankton and their correlation with physico-chemical conditions of water. A total of 64 phytoplankton belonging to bacillariophyceae, chlorophyceae, cyanophyceae and euglenophyceae were identified. Phytoplankton in general, showed two growth periods, one in spring and other in winter. A clear dominance of bacillariophyceae over chlorophyceae, cyanophyceae and euglenophyceae was observed throughout the study period. Navicula spp. with population density of 118 no./ml was recorded to be the most abundant species amongst bacillariophyceae at the selected site. Chlorophyceae formed the second most dominant group of phytoplankton with Chlorella spp. (112 no./ml) as the most abundant species. Osillatoria spp. with population density of 119 no./ml was found to be the most abundant amongst cyanophyceae. Euglenophyceae formed the least represented group of phytoplankton with peak population in spring. Statistically, bacillariophyceae and euglenophyceae showed significant negative correlation (r = -0.855 and r = -0.177) with water temperature, while cyanophyceae showed significant positive correlation (r = 0.745). Chlorophyceae showed non-significant positive correlation (r = 0.325) with water temperature at the selected site. Shannon-Wiener diversity index (H′) value (1.672) was recorded for cyanophyceae, while the highest evenness (J′) value (0.8872) was recorded for euglenophyceae. The value of Berger-Parker index of dominance (0.1859) was highest for bacillariophyceae. Canonical correspondance analysis (CCA) was also carried out to analyze the relationship between the physico-chemical parameters and the phytoplankton. It showed that the most important factors affecting phytoplankton distribution are water temperature, CO2, chloride, transparency, TDS, alkalinity and dissolved oxygen. Key words: Biodiversity, freshwater bodies, phytoplankton, Wular Lake.

Persistence in the desert: ephemeral waterways and small‐scale gene flow in the desert spring amphipod, Wangiannachiltonia guzikae

Summary The springs of the Great Artesian Basin (GAB) in central Australia support a unique, but threatened ecosystem adapted to permanent fresh water in a desert landscape. Taxa within these springs are short‐range endemics, with very limited distributions, making them highly susceptible to extinction. Knowledge of fine‐scale dispersal mechanisms will help to develop conservation management plans that maintain gene flow and, by extension, the genetic diversity of these populations. This study focused on determining dispersal capabilities of the endemic GAB spring amphipod, Wangiannachiltonia guzikae, in an area &lt;4 km2. Using 11 microsatellite loci, 288 individuals were genotyped from 14 springs. Despite the very small area, low levels of gene flow and significant population differences were found among individual spring populations. Microgeographical genetic structure is clearly evident, and fine‐scale dispersal is significantly correlated with temporary waterways between springs. This pattern of genetic divergence supports the stream hierarchy model of population structure and suggests that connectivity between springs is critical for gene flow, although the precise mechanism of dispersal is still open for interpretation.