Changes In Timing Of Migration Research Articles

Flexibility of Timing of Avian Migration to Climate Change Masked by Environmental Constraints En Route

During the past decades, phenology of many organisms has advanced in response to climate change [1]. Earlier arrival of long-distance migrants has been reported frequently [2, 3], but advancements of arrival and breeding were not always sufficient to match phenology at other trophic levels [4]. This has led to increased selection for early breeding [5] and severe population declines [6, 7]. This inadequate response has been explained by an inflexible start of migration, governed by cues unrelated to climate change, such as photoperiod [8]. It has been suggested that evolution at the genetic level is required for a change in photoresponsiveness [9]. Recently, such an evolutionary change in migration timing was suggested [10]. Here I show that timing of spring migration of pied flycatchers (Ficedula hypoleuca) has responded flexibly to climate change. Recovery dates during spring migration in Northern Africa advanced by ten days between 1980 and 2002, which was explained by improving Sahel rainfall and a phenotypic effect of birth date. The lack of advance on the breeding grounds most likely was due to environmental constraints during migration. Adjustment of arrival date in migrants to climate change could thus be rapid, but only if circumstances favorably change for the whole journey.

Populations of migratory bird species that did not show a phenological response to climate change are declining

Recent rapid climatic changes are associated with dramatic changes in phenology of plants and animals, with optimal timing of reproduction advancing considerably in the northern hemisphere. However, some species may not have advanced their timing of breeding sufficiently to continue reproducing optimally relative to the occurrence of peak food availability, thus becoming mismatched compared with their food sources. The degree of mismatch may differ among species, and species with greater mismatch may be characterized by declining populations. Here we relate changes in spring migration timing by 100 European bird species since 1960, considered as an index of the phenological response of bird species to recent climate change, to their population trends. Species that declined in the period 1990-2000 did not advance their spring migration, whereas those with stable or increasing populations advanced their migration considerably. On the other hand, population trends during 1970-1990 were predicted by breeding habitat type, northernmost breeding latitude, and winter range (with species of agricultural habitat, breeding at northern latitudes, and wintering in Africa showing an unfavorable conservation status), but not by change in migration timing. The association between population trend in 1990-2000 and change in migration phenology was not confounded by any of the previously identified predictors of population trends in birds, or by similarity in phenotype among taxa due to common descent. Our findings imply that ecological factors affecting population trends can change over time and suggest that ongoing climatic changes will increasingly threaten vulnerable migratory bird species, augmenting their extinction risk.

Trends in timing of migration of south-western Australian birds and their relationship to climate

The influence of climate on the timing of migration of Australian birds is poorly understood, particularly in Western Australia and for waterfowl. This paper examines a new dataset, comprising presence—absence records of 20 species of waterbirds and landbirds at Middlesex, south-western Australia, for the period 1973–2000. Considering only species with sufficient records to determine trends, over this period nine of 19 species (47%) had significantly altered arrival times (five arriving earlier and four later); seven of 17 species (41%) had significant changes in departure dates (four departing later, three earlier); and eight of 17 (47%) species had significantly different season lengths (the period spent at Middlesex, with five spending more time at Middlesex). Generally, changes in the timing of regular seasonal movements were consistent among species that arrived or departed in similar seasons, with species that arrive in spring tending to arrive earlier, while species arriving in autumn and winter arrived later. Trends were generally more pronounced in spring-arriving species, though strong trends were also seen in other seasons. This region experienced significant reductions in the number of rain-days and increased minimum temperature over the study period. For many Middlesex species, particularly waterbirds, precipitation changes appeared to have a greater influence on changes in migration timing than temperature, though some species also appeared to respond to changes in extreme temperatures. This differs from many northern hemisphere studies, where changes in mean, maximum, or minimum temperature were associated with changes in migration timing.

Through-a-chip partial filling affinity capillary electrophoresis for estimating binding constants of ligands to receptors

In this paper, we describe the development of a microfluidic/capillary electrophoresis (CE) technique employing partial filling affinity capillary electrophoresis (PFACE) to estimate binding constants of ligands to receptors using as model systems carbonic anhydrase B (CAB, EC 4.2.1.1) and vancomycin from Streptomyces orientalis. Using multilayer soft lithography (MSL), a microfluidic device (MD) consisting of fluid and control channels is fabricated and fitted with an external capillary column. Multiple flow channels allows for manipulation of a zone of ligand and sample containing receptor and non-interacting standards into the MD and subsequently into the capillary column. Upon electrophoresis the sample components migrate into the zone of ligand where equilibrium is established. Changes in migration time of the receptor are used in the analysis to obtain a value for the binding interaction. The manipulation of small volumes of solution on the MD minimizes the need of time-consuming pipetting steps.

The interaction between severe acute respiratory syndrome coronavirus 3C-like proteinase and a dimeric inhibitor by capillary electrophoresis

3C-like proteinase of severe acute respiratory syndrome (SARS) coronavirus has been demonstrated to be a key target for drug design against SARS. The interaction between SARS coronavirus 3C-like (3CL) proteinase and an octapeptide interface inhibitor was studied by affinity capillary electrophoresis (ACE). The binding constants were estimated by the change of migration time of the analytes in the buffer solution containing different concentrations of SARS 3CL proteinase. The results showed that SARS 3CL proteinase was able to complex with the octapeptide competitively, with binding constants of 2.44 × 10 4 M −1 at 20 °C and 2.11 × 10 4 M −1 at 37 °C. In addition, the thermodynamic parameters deduced reveal that hydrophobic interaction might play major roles, along with electrostatic force, in the binding process. The ACE method used here could be developed to be an effective and simple way of applying large-scale drug screening and evaluation.

Growing season changes in Fennoscandia and Kola peninsula during the period 1982 to 1999 - Implications for reindeer husbandry (In Norwegian with Summary in English)

Growing season changes in Fennoscandia and Kola peninsula during the period 1982 to 1999 - Implications for reindeer husbandry (In Norwegian with Summary in English)

Long-term changes in migration timing of adult Atlantic salmon (Salmo salar) at the southern edge of the species distribution

The Connecticut River historically represented the southernmost extent of the North American range of Atlantic salmon (Salmo salar), but the native population was extirpated 200 years ago by dam construction. An extensive restoration effort has relied upon stock transfers from more northerly rivers, especially the Penobscot River (Maine). Recent work has shown differences in age structure between donor and derivative populations. Here we focus on a related life-history trait, the timing of the adult migration. We examined 23 years of migration timing data collected at two capture locations in the Connecticut River drainage. We found that both dates of first capture and median capture dates have shifted significantly earlier by about 0.5 days·year–1. To conclude whether this is a consequence of local adaptation or a coast-wide effect, we also quantified changes in migration timing of more northerly stocks (in Maine and Canada). We found that the changes in migration timing were not unique to the Connecticut River stock and instead observed coherent patterns in the shift towards earlier peak migration dates across systems. These consistent shifts are correlated with long-term changes in temperature and flow and may represent a response to global climate change.

Study on the interactions between anti-HIV-1 active compounds with trans-activation response RNA by affinity capillary electrophoresis

The study on the interactions between two anti-human immunodeficiency virus type 1 (anti-HIV-1) active compounds with trans-activation response (TAR) RNA by affinity capillary electrophoresis (ACE) with UV absorbance detection is presented. The results showed that the novel active molecules could interact with TAR RNA and inhibit the reproduce process of HIV-1. The binding constants were estimated by the change of migration time of the analytes through the change of concentrations of TAR RNA in the buffer solution. The yielded binding constants of 8.87 × 10 3 M −1 for active compound C 3 and 8.42 × 10 3 M −1 for MC 3 at 20.0 °C, 0.626 × 10 3 M −1 and 0.644 × 10 3 M −1 at 37.0 °C, respectively. The thermodynamic parameters Δ H and Δ S were obtained and shown that both hydrophobic and electrostatic interaction played roles in the binding processes. The results showed that the presented method was an easy and simple method to evaluate the interaction of small molecules with some bioactive materials.

Change of migration time and separation window accompanied by field-enhanced sample stacking in capillary zone electrophoresis

When field-enhanced sample stacking was used in capillary zone electrophoresis (CZE) analysis of cations, the decrease of migration time and the reduction of separation window was observed with increase of sample plug length. A simple equation expressing the migration velocity in the stacking process was derived to explain the above phenomenon. From experiments and theoretical consideration, we confirmed that this effect was caused by the higher potential gradient and larger eletroosmotic flow (EOF) mobility at the sample plug than those at the supporting electrolyte. A mathematical model appropriate for the computer simulation of such a system was studied considering the experimental results, and it was concluded that electroosmotic velocity (v(eof)) should be introduced to the equation of continuity as a constant.

Use of capillary electrophoresis in the study of ligand-DNA interactions.

Free solution capillary electrophoresis (FSCE) has been used to separate two non-self-complementary 12mer oligonucleotide duplexes: d(AAATTATATTAT).d(ATAA-TATAATTT) and d(GGGCCGCGCCGC).d(GCGGCGCGGCCC). Titration of mixtures of the two oligonucleotides with model intercalators (ethidium bromide andactinomycin D) and minor groove binders (netropsin, Hoechst 33258 and distamycin) has shown the suitability of FSCE as a method to study the sequence selectivity of DNA binding agents. Binding data have shown cooperativity of binding for netropsin and Hoechst 33258 and have provided ligand:DNA binding ratios for all five compounds. Cooperativity of netropsin binding to a 12mer with two potential sites has been demonstrated for the first time. Ligands binding in the minor groove caused changes in migration time and peak shape which were significantly different from those caused by intercalators.

Capillary electrophoresis of glutamate and aspartate in rat brain dialysate Improvements in detection and analysis time using cyclodextrins

Addition of cyclodextrins (CDs) to the electrolyte buffer in the capillary zone electrophoresis (CZE) separation of derivatized amino acids was evaluated in terms of fluorescence signal enhancement, resolution, and migration time effects. Maximum fluorescence signal enhancement was observed with separation buffers containing 4M β-cyclodextrin or 10 m M hydroxypropyl β-cyclodextrin. Resolution values decreased as the CD concentrations increased. Migration times were dependent on CD concentration. Inclusion complex formation constants calculated using changes in migration time showed slight agreement with those calculated by the steady-state fluorescence enhancement technique. Analysis of 20 μl of rat brain microdialysate by CZE using 4 m M β-cyclodextrin in borate buffer resulted in baseline resolution of glutamate and aspartate in 3.6 min. The results of this work indicate that, when used as separation buffer additives, cyclodextrins are capable of increasing the fluorescence signal and decreasing the migration times of NDA-derivatized acidic amino acids.

Application of Nonaqueous Capillary Electrophoresis to the Separation of Long-Chain Surfactants

The potential of nonaqueous capillary electrophoresis (CE) for the separation of hydrophobic solutes has been examined for a series of alkanesulfonates (C2−C16 ), alkyl sulfates (C8−C18), and linear alkyl benzenesulfonates. Sample loss and band broadening observed in aqueous CE separations was not observed in nonaqueous systems. Changes in separation selectivity induced by solvation and ion pair effects were examined. Separation selectivity was affected by changes in solvation and by a change from protic (methanol) to aprotic conditions (addition of acetonitrile). The addition of alkali metal ion caused changes in migration time via ion pairing but had only small effects on separation selectivity. However, the adjustment of the hydrophobicity of the electrolyte counterion was effective for separation optimization. The analytical features of these nonaqueous systems and applications to samples of shampoo, liquid detergent, and laundry detergents were also briefly examined. Alkanesulfonates and alkyl sulfates were separated in 0.01 mol/L sodium p-toluenesulfonate and 0.005 mol/L p-toluenesulfonic acid in methanol and in methanol/acetonitrile mixtures with indirect UV detection at 214 nm. Linear alkyl benzenesulfonates were separated in methanol and methanol/acetonitrile mixtures with tetramethylammonium as a counterion and direct detection at 214 nm.

Precision in capillary electrophoresis with respect to quantitative analysis of suramin

Suramin is an important anti-tumor and anti-viral chemotherapeutic agent. We have previously presented a capillary electrophoresis (CE) method for its quantitative analysis, where its quantitation was linear over three orders of magnitude, with good precision (1.8%) and accuracy. The constantly varying electroosmotic properties of the capillary due to various causes such as analyte adsorption to the inner wall, affect the migration times of analytes during consecutive electrophoresis runs. This results in progressive changes in analyte peak areas, causing less desirable or unacceptable CE assay precision. This paper illustrates a strategy to overcome the problem of assay reproducibility by using an internal standard whose migration time is short and close to that of the analyte so that the relative change of migration time is minimized. Assay precisions as good as 0.3% were observed in these experiments. These results are in agreement with the theoretical basis of experimental capillary electrophoresis.

The Effect of Column Temperature on the Migration Time of Peptides in Free-Solution Capillary Electrophoresis

Abstract The effect of column temperature on the migration times of peptides in free - solution capillary electrophoresis (FSCE) is discussed. It has been found that there are parallel iinear relationships between the logarithm of the migration time and the reciprocal of column temperature. The changes in migration time with temperature for the peptides are predominantly due to the temperature - induced viscosity changes of water. The elec-trophoretic selectivity remains constant for a specific pair of peptides despite a considerable variation in the migration time for each of the peptides in FSCE.

Significance of haemolymph juvenile hormone titer changes in timing of migration and reproduction in adult Oncopeltus fasciatus

Previous studies had shown that both migratory flight and ovarian maturation in Oncopeltus fasciatus were stimulated by juvenile hormone (JH), yet the two behaviors were mutually exclusive. To understand the relationship of this hormone to these behaviors, haemolymph juvenile hormone titers were determined in both sexes of Oncopeltus throughout the adult stage by the Manduca pigmentation bioassay. Animals reared under long day conditions (17L:7D, 24°C) showed an immediate rise in haemolymph titers of JH after adult emergence whereas those reared in a short day photoperiod (12L:12D, 24°C) had a more gradual increase in hormone titers. Migratory flight behavior occurred during periods of intermediate hormone titers while oviposition did not begin until JH titers had reached their peak. It was concluded that lower JH titers normally stimulate flight in the prereproductive adult whereas higher titers are required for complete ovarian development. The corpus allatum in Oncopeltus thus coordinates migration and reproduction in response to the environmental cues of photoperiod, temperature, and food quality.