Non-native Environments Research Articles

The role of the backbone torsion in protein folding

BackgroundThe set of forces and sequence of events that govern the transition from an unfolded polypeptide chain to a functional protein with correct spatial structure remain incompletely known, despite the importance of the problem and decades of theory development, computer simulations, and laboratory experiments. Information about the correctly folded state of most proteins is likely to be present in their sequences, and yet many proteins fail to attain native structure after overexpression in a non-native environment or upon experimental denaturation and refolding.Presentation of the hypothesisWe hypothesize that correct protein folding in vivo is an active, energy-dependent process that most likely applies torque force co-translationally to all proteins and possibly also post-translationally to many proteins in every cell. When a site on an unfolded polypeptide is rotationally constrained, torsion applied at another site would induce twisting of the main chain, which would initiate the formation of a local secondary structure, such as an alpha-helical turn or a beta-turn/beta-hairpin. The nucleation of structural elements is a rate-limiting, energetically unfavorable step in the process of protein folding, and energy-dependent chain torsion is likely to help overcome this barrier in vivo. Several molecular machines in a cell, primarily ribosomes, but also possibly signal recognition particles and chaperone systems, may play a role in applying torque to an unfolded protein chain, using the energy of GTP or ATP hydrolysis. Lack of such force in the in vitro systems may be the main reason of the failure of many longer proteins to attain the correct functional conformation.Testing the hypothesisThe hypothesis can be tested using single-molecule approaches, by measuring directly the forces applied to polypeptide chains under controlled conditions in vitro, and in bulk, by assessing folding rates and extent of misfolding in proteins that are engineered to experience transient spatial constraint during their synthesis.Implications of the hypothesisLearning about the role of main chain torsion in protein folding will improve our understanding of folding mechanisms and may lead to bioengineering solutions that would enhance the yields of correctly folded proteins in heterologous expression systems.ReviewersThis article was reviewed by Frank Eisenhaber, Igor Berezovsky and Michael Gromiha.

On the mechanism of ubiquinone mediated photocurrent generation by a reaction center based photocathode

Upon photoexcitation, the reaction center (RC) pigment-proteins that facilitate natural photosynthesis achieve a metastable separation of electrical charge among the embedded cofactors. Because of the high quantum efficiency of this process, there is a growing interest in their incorporation into biohybrid materials for solar energy conversion, bioelectronics and biosensing. Multiple bioelectrochemical studies have shown that reaction centers from various photosynthetic organisms can be interfaced with diverse electrode materials for the generation of photocurrents, but many mechanistic aspects of native protein functionality in a non-native environment is unknown. In vivo, RC's catalyse ubiquinone-10 reduction, protonation and exchange with other lipid phase ubiquinone-10s via protein-controlled spatial orientation and protein rearrangement. In contrast, the mechanism of ubiquinone-0 reduction, used to facilitate fast RC turnover in an aqueous photoelectrochemical cell (PEC), may not proceed via the same pathway as the native cofactor.In this report we show truncation of the native isoprene tail results in larger RC turnover rates in a PEC despite the removal of the tail's purported role of ubiquinone headgroup orientation and binding. Through the use of reaction centers with single or double mutations, we also show the extent to which two-electron/two-proton ubiquinone chemistry that operates in vivo also underpins the ubiquinone-0 reduction by surface-adsorbed RCs in a PEC. This reveals that only the ubiquinone headgroup is critical to the fast turnover of the RC in a PEC and provides insight into design principles for the development of new biophotovoltaic cells and biosensors.

Social context, but not individual personality, alters immigrant viability in a spider with mixed social structure

Immigrant viability is a major determinant of the realized rate of gene flow across populations. For social organisms, the social context in which immigrants disperse across contrasting environments may have important implications for their viability post dispersal. Here, we use social spiders whose individual personalities as well as group personality compositions vary across sites to test whether the strength of selection against immigrants (i.e. mortality rates) differs depending on whether spiders are transplanted (1) as individuals and remain alone, (2) join pre-existing colonies at their new non-native environment, or (3) move with their native group. We also tested for an effect of individual personality on survival. We found that social context, and not individual personality, affects individual survival in foreign environments with contrasting resource levels. Individuals that were transplanted with their native groups suffered higher mortality rates compared to individuals transplanted as singletons, regardless of whether or not they were assimilated into native colonies. Moving as individuals could thus provide an avenue for ongoing gene flow among populations from different resource environments. We found no depressed performance of control colonies that were transplanted across sites with resource levels similar to each colony's site of origin. These results are at odds with the intuition that dispersing as a group should generally enhance the viability of immigrants, at least in social species. We propose that these results could be explained by a mismatch in the ideal group compositions (personality compositions) favoured in different environments, despite a lack of selection on individual personality traits. These results provide a first glimpse into the relative roles of individual personality and social context in mediating gene flow among populations from divergent environments.

Assessing the physiological relevance of alternate architectures of the p7 protein of hepatitis C virus in different environments

The viroporin p7 of the hepatitis C virus forms multimeric channels eligible for ion transport across the endoplasmic reticulum membrane. Currently the subject of many studies and discussion, the molecular assembly of the ion channel and the structural characteristics of the p7 monomer are not yet fully understood. Structural investigation of p7 has been carried out only in detergent environments, making the interpretation of the experimental results somewhat questionable. Here, we analyze by means of molecular dynamics simulations the structure of the p7 monomer as a function of its sequence, initial conformation and environment. We investigate the conductance properties of three models of a hexameric p7 ion channel by examining ion translocation in a pure lipid bilayer. It is noteworthy that although none of the models reflects the experimentally observed trend to conduct preferentially cations, we were able to identify the position and orientation of titratable acidic or basic residues playing a crucial role in ion selectivity and in the overall conductance of the channel. In addition, too compact a packing of the monomers leads to channel collapse rather than formation of a reasonable pore, amenable to ion translocation. The present findings are envisioned to help assess the physiological relevance of p7 ion channel models consisting of multimeric structures obtained in non-native environments.

What do we really know about alien plant invasion? A review of the invasion mechanism of one of the world's worst weeds.

This review provides an insight into alien plant invasion taking into account the invasion mechanism of parthenium weed ( Parthenium hysterophorus L.). A multi-lateral understanding of the invasion biology of this weed has pragmatic implications for weed ecology and management. Biological invasions are one of the major drivers of restructuring and malfunctioning of ecosystems. Invasive plant species not only change the dynamics of species composition and biodiversity but also hinder the system productivity and efficiency in invaded regions. Parthenium weed, a well-known noxious invasive species, has invaded diverse climatic and biogeographic regions in more than 40 countries across five continents. Efforts are under way to minimize the parthenium weed-induced environmental, agricultural, social, and economic impacts. However, insufficient information regarding its invasion mechanism and interference with ecosystem stability is available. It is hard to devise effective management strategies without understanding the invasion process. Here, we reviewed the mechanism of parthenium weed invasion. Our main conclusions are: (1) morphological advantages, unique reproductive biology, competitive ability, escape from natural enemies in non-native regions, and a C3/C4 photosynthesis are all likely to be involvedin parthenium weed invasiveness. (2) Tolerance to abiotic stresses and ability to grow in wide range of edaphic conditions are thought to be additional invasion tools on a physiological front. (3) An allelopathic potential of parthenium weed against crop, weed and pasture species, with multiple modes of allelochemical expression, may also be responsible for its invasion success. Moreover, the release of novel allelochemicals in non-native environments might have a pivotal role in parthenium weed invasion. (4) Genetic diversity found among different populations and biotypes of parthenium weed, based on geographic, edaphic, climatic, and ecological ranges, might also be a strong contributor towards its invasion success. (5) Rising temperatures and atmospheric carbon dioxide (CO2) concentrations and changing rainfall patterns, all within the present day climate change prediction range are favorable for parthenium weed growth, its reproductive output, and therefore its future spread and infestation. (6) Parthenium weed invasion in South Asia depicts the relative and overlapping contribution of all the above-mentioned mechanisms. Such an understanding of the core phenomena regulating the invasion biology has pragmatic implications for its management. A better understanding of the interaction of physiological processes, ecological functions, and genetic makeup within a range of environments may help to devise appropriate management strategies for parthenium weed.

Plasticity and evolution in correlated suites of traits.

When organisms are faced with new or changing environments, a central challenge is the coordination of adaptive shifts in many different phenotypic traits. Relationships among traits may facilitate or constrain evolutionary responses to selection, depending on whether the direction of selection is aligned or opposed to the pattern of trait correlations. Attempts to predict evolutionary potential in correlated traits generally assume that correlations are stable across time and space; however, increasing evidence suggests that this may not be the case, and flexibility in trait correlations could bias evolutionary trajectories. We examined genetic and environmental influences on variation and covariation in a suite of behavioural traits to understand if and how flexibility in trait correlations influences adaptation to novel environments. We tested the role of genetic and environmental influences on behavioural trait correlations by comparing Trinidadian guppies (Poecilia reticulata) historically adapted to high- and low-predation environments that were reared under native and non-native environmental conditions. Both high- and low-predation fish exhibited increased behavioural variance when reared under non-native vs. native environmental conditions, and rearing in the non-native environment shifted the major axis of variation among behaviours. Our findings emphasize that trait correlations observed in one population or environment may not predict correlations in another and that environmentally induced plasticity in correlations may bias evolutionary divergence in novel environments.

Divergent natural selection promotes immigrant inviability at early and late stages of evolutionary divergence.

Natural selection's role in speciation has been of fundamental importance since Darwin first outlined his theory. Recently, work has focused on understanding how selection drives trait divergence, and subsequently reproductive isolation. "Immigrant inviability," a barrier that arises from selection against immigrants in their nonnative environment, appears to be of particular importance. Although immigrant inviability is likely ubiquitous, we know relatively little about how selection acts on traits to drive immigrant inviability, and how important immigrant inviability is at early-versus-late stages of divergence. We present a study evaluating the role of predation in the evolution of immigrant inviability in recently diverged population pairs and a well-established species pair of Brachyrhaphis fishes. We evaluate performance in a high-predation environment by assessing survival in the presence of a predator, and swimming endurance in a low-predation environment. We find strong signatures of local adaptation and immigrant inviability of roughly the same magnitude both early and late in divergence. We find remarkably conserved selection for burst-speed swimming (important in predator evasion), and selection for increased size in low-predation environments. Our results highlight the consistency with which selection acts during speciation, and suggest that similar factors might promote initial population differentiation and maintain differentiation at late stages of divergence.

Monk parakeet invasion success: a role for nest thermoregulation and bactericidal potential of plant nest material?

Invasive species are a global threat to biodiversity, economy and human wellbeing. To mitigate these threats, identifying and halting the introduction of potentially invasive species is crucial. Although progress has been made in elucidating mechanisms underlying invasion success, the role of species behavioral strategies has only received scant attention. Here, we use the invasion of monk parakeets in Santa Catarina state, southern Brazil to study whether behavioral strategies such as nest thermoregulation and the ability to self-medicate against pathogens contribute to the establishment success of invading species. We relate data on monk parakeet reproductive success to ambient temperatures in- and outside nesting chambers and test the bactericidal potential of plants transported to the nest by breeding monk parakeets. Compared to breeding data from other invaded ranges and parts of the species’ native range, our results suggest both thermoregulation and the use of bactericidal plants could potentially influence monk parakeet reproductive success. Thermoregulation maintains stable temperatures of incubator chambers compared to large fluctuations (especially hotter extremes) outside the nest. At least one of the plants brought to the nest effectively inhibited growth of pathogenic bacteria. The union of these two factors could increase reproductive rates and may consequently aid the expansion of the species in new non-native environments.

Invaded Invaders: Infection of Invasive Brown Treesnakes on Guam by an Exotic Larval Cestode with a Life Cycle Comprised of Non-Native Hosts.

BackgroundMultiple host introductions to the same non-native environment have the potential to complete life cycles of parasites incidentally transported with them. Our goal was to identify a recently detected parasitic flatworm in the invasive Brown Treesnake (Boiga irregularis) on the remote Pacific island of Guam. We considered possible factors influencing parasite transmission, and tested for correlations between infection status and potential indicators of host fitness. We used genetic data from the parasite and information about the native ranges of other possible non-native hosts to hypothesize how it arrived on Guam and how its life cycle may be currently supported.MethodsWe identified the parasite by comparing larval morphology and mtDNA sequences with other Pseudophyllid tapeworms. We assessed probability of infection in individual snakes using logistic regression and examined different factors influencing presence of parasites in hosts.ResultsWe identified the parasite as the pseudophyllid cestode Spirometra erinaceieuropaei, with all sampled worms from multiple snakes sharing a single mtDNA haplotype. Infection appears to be limited to the only freshwater watershed on the island, where infection prevalence was high (77.5%). Larger snakes had a higher probability of being infected, consistent with the chronic nature of such infections. While infection status was positively correlated with body condition, infected snakes tended to have lower intra-peritoneal fat body mass, potentially indicating a negative effect on energy stores.ConclusionsWe discovered that B. irregularis inhabiting a small area of forested habitat in a freshwater watershed on Guam are often infected by a novel parasite of Asian origin. While further work is needed, this species of Spirometra, itself a non-native species, likely depends on a suite of recently introduced hosts from different parts of the world to complete the life cycle. This baseline study provides little evidence of any effects on host fitness, but additional data are needed to more thoroughly explore the consequences of infection in this invasive snake population.

Reproductive periodicity and larval vertical migration behavior of European green crab Carcinus maenas in a non-native habitat

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 536:123-134 (2015) - DOI: https://doi.org/10.3354/meps11422 Reproductive periodicity and larval vertical migration behavior of European green crab Carcinus maenas in a non-native habitat Claudio DiBacco1,*, Thomas W. Therriault2 1Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2, Canada 2Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC, V9T 6N7, Canada *Corresponding author: claudio.dibacco@dfo-mpo.gc.ca ABSTRACT: The reproductive periodicity and vertical migration behavior of the European green crab Carcinus maenas in a non-native environment were characterized and the implications for invasion dynamics highlighted. Biweekly to monthly trap surveys in Pipestem Inlet, British Columbia, revealed ovigerous crabs from mid-February to June 2007. Concurrent meroplankton surveys confirmed green crab zoeae by mid-April, about 1 mo following peak abundance of ovigerous crabs (March 2007). All 4 zoeal stages of development were sampled between March and December 2007, but >95% were Stage I zoeae sampled between April and August. Vertical meroplankton surveys conducted in 2008 revealed diel-mediated vertical migratory (DVM) behavior; however the majority of sampled zoeae were aggregated near the pycnocline in surface outflowing waters. Negligible densities of post-Stage I zoeae (<1%) support the observation of zoeal export from Pipestem Inlet. Tidal-mediated vertical migratory behavior, characteristic in native European populations, was not observed in Pipestem Inlet. In contrast, low larval densities were sampled in surface (<1 m) and deep (>8 m) sampling strata. We hypothesize that low surface salinity (17-19 psu) and cold temperature (<12°C below the pycnocline) in deep strata constrained DVM. Our results highlight a need for better characterization of reproductive periodicity and zoeal migratory behavior in non-native habitats, which has implications for improving predictions of secondary spread and range expansion rates mediated via larval dispersal dynamics. KEY WORDS: Invasive · Non-native · European green crab · Carcinus maenas · Larval abundance · Dispersal · Reproductive periodicity · Vertical migration behavior Full text in pdf format PreviousNextCite this article as: DiBacco C, Therriault TW (2015) Reproductive periodicity and larval vertical migration behavior of European green crab Carcinus maenas in a non-native habitat. Mar Ecol Prog Ser 536:123-134. https://doi.org/10.3354/meps11422 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 536. Online publication date: September 29, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Teaching Arabic oral and written communication among the Yoruba speakers in Nigeria: A constrastive analysis

The teaching and learning of Arabic language especially in the non-native environment require a simplified method to make the job a more fruitful enterprise. This paper explores the application of a contrastive analysis of both the target language and the native language in encouraging, motivating and simplifying the teaching and learning of oral Arabic communication skill among the native Yoruba speakers. The work identifies the major areas of difficulties facing the students from this region. This includes phonetics, phonology and agreement relation (otherwise known as concord in grammar). The agreement consists of gender, person, terms and numbers which form a major component of grammatical Arabic sentence. It is observed that understanding these major areas will enhance the performance of the students in achieving the required standard in Arabic oral communication. The paper concludes that Arabic phonetics, phonology and grammar are more elaborate than those of Yoruba. Hence, the instructors need to focus more attention on these difficult areas; especially those areas that do not exist in the native language (Yoruba).

Local adaptation and divergence in colour signal conspicuousness between monomorphic and polymorphic lineages in a lizard.

Population differences in visual environment can lead to divergence in multiple components of animal coloration including signalling traits and colour patterns important for camouflage. Divergence may reflect selection imposed by different receivers (conspecifics, predators), which depends in turn on the location of the colour patch. We tested for local adaptation of two genetically and phenotypically divergent lineages of a rock-inhabiting lizard, Ctenophorus decresii, by comparing the visual contrast of colour patches to different receivers in native and non-native environments. The lineages differ most notably in male throat coloration, which is polymorphic in the northern lineage and monomorphic in the southern lineage, but also differ in dorsal and lateral coloration, which is visible to both conspecifics and potential predators. Using models of animal colour vision, we assessed whether lineage-specific throat, dorsal and lateral coloration enhanced conspicuousness to conspecifics, increased crypsis to birds or both, respectively, when viewed against the predominant backgrounds from each lineage. Throat colours were no more conspicuous against native than non-native rock but contrasted more strongly with native lichen, which occurs patchily on rocks inhabited by C.decresii. Conversely, neck coloration (lateral) more closely matched native lichen. Furthermore, although dorsal coloration of southern males was consistently more conspicuous to birds than that of northern males, both lineages had similar absolute conspicuousness against their native backgrounds. Combined, our results are consistent with local adaptation of multiple colour traits in relation to multiple receivers, suggesting that geographic variation in background colour has influenced the evolution of lineage-specific coloration in C.decresii.

NMR structures of membrane proteins in phospholipid bilayers.

Membrane proteins have always presented technical challenges for structural studies because of their requirement for a lipid environment. Multiple approaches exist including X-ray crystallography and electron microscopy that can give significant insights into their structure and function. However, nuclear magnetic resonance (NMR) is unique in that it offers the possibility of determining the structures of unmodified membrane proteins in their native environment of phospholipid bilayers under physiological conditions. Furthermore, NMR enables the characterization of the structure and dynamics of backbone and side chain sites of the proteins alone and in complexes with both small molecules and other biopolymers. The learning curve has been steep for the field as most initial studies were performed under non-native environments using modified proteins until ultimately progress in both techniques and instrumentation led to the possibility of examining unmodified membrane proteins in phospholipid bilayers under physiological conditions. This review aims to provide an overview of the development and application of NMR to membrane proteins. It highlights some of the most significant structural milestones that have been reached by NMR spectroscopy of membrane proteins, especially those accomplished with the proteins in phospholipid bilayer environments where they function.

Immigration as a Catalyst for Increased Health Awareness: Immigrant Women Define Health and Health Decision Making

In this study we discuss how immigrant women define and maintain health, particularly breast health. Using a grounded theory approach, we conducted twenty in-depth interviews with immigrant women in Canada. The main theme that emerged from the data was immigration as a catalyst for increased health awareness. Three thematic constructs describe how the women maintain health and make health decisions in a nonnative environment: the belief that health is a combination of physical and mental health, independence, and good environment; the belief that culture and relationships influence health decision making; and the belief that health care accessibility impacts health behaviors.

Investigating Lag Phase and Invasion Potential of Vitex rotundifolia: A Coastal Dune Exotic

Murren, C.J.; Purvis, K.G.; Glasgow, D.; Messervy, J.; Penrod, M., and Strand, A.E., 2014. Investigating lag phase and invasion potential of Vitex rotundifolia: a coastal dune exotic. After initial establishment in nonnative environments, exotic species are often found in low numbers for long periods of time. After a lag phase, a transition to an exponential growth phase is characteristic. A broad question remains: Can we identify factors that contribute to the lag phase or assess the potential for additional invasion? Our approach employed a case study of V. rotundifolia (beach vitex), a nonnative dune plant introduced in the late 1980s to North and South Carolina. We performed manipulative and observational experiments on the sexual and asexual reproductive ecology, mating system, seed ecology, and pollination ecology to assess the possibility of additional invasion potential and to gain an understanding of potential among population variation and among site ecological variation that could contribute to a transition from lag to exponential spread phases. We found that vegetative reproduction, sexual reproduction, and viable seed set rates are high, and there is future potential for spread through vegetative reproduction as not all the ovules set seed. Pollinator activity varied by year and was consistent with increased fruit and seed set, indicating a likely mechanism contributing to current sexual reproductive success. Germination rate was low, but given the high numbers of seeds produced per square meter, we estimate an average of 13 new germinants m−2 y−1. On the basis of our observations, we found the potential for increased reproductive success and increased invasion potential. Management practices that minimize vegetative expansion from nearby sites and through seed dispersal are the highest priority.

Englishising African cultures: revisiting acculturated forms of English in Botswana

Many ‘African English’ researchers (see Kachru, B. B. (1983). The Indianization of English. The English language in India. Singapore: Singapore University Press.) have argued that when English is used in non-native environments, many aspects of its lexicon, grammar and pronunciation are modified and ‘acculturated’ to suit the local culture. However, Bagwasi challenges such an interpretation of the modifications that the English language undergoes in non-native environments. She argues that most of these modifications of English in African settings support englishisation of African culture rather than africanisation of the English language. She argues that some of the acclaimed acculturated forms fall short of representing local culture and local practices, but instead represent English practices and value systems. She further argues that in situations where English is used in African contexts, African values, perspectives and viewpoints are compromised and distorted while English values, perspectives and viewpoints are adopted and promoted. The current paper is a follow-up and further development of that argument. It lends further evidence to the argument by analysing English and Setswana terms referring to kinship, colours and seasons. The findings contradict the commonly held belief that speakers of English in Africa are able to shift, extend or restrict English forms so that they are able to express African meanings and culture.

Introduced American eels Anguilla rostrata in European waters: life-history traits in a non-native environment.

This study investigated growth, condition and development of American eels Anguilla rostrata that were introduced into a European river to estimate their competitive potential in a non-native habitat. Results demonstrate that A. rostrata develops normally in European waters and successfully competes with the native European eel Anguilla anguilla. In addition, A. rostrata appears to be more susceptible to the Asian swimbladder nematode Anguillicola crassus than A. anguilla and could support the further propagation of this parasite. Detected differences in fat content and gonad mass between Anguilla species are assumed to reflect species-specific adaptations to spawning migration distances. This study indicates that A. rostrata is a potential competitor for the native fauna in European fresh waters and suggests strict import regulations to prevent additional pressure on A. anguilla and a potential further deterioration of its stock situation.

Rapid cold hardening response in the predatory mite Neoseiulus californicus

We investigated the rapid cold hardening (RCH) response in the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). On direct exposure, ≤2 % of adult females survived -10 °C for 2 h. However, when acclimatized first at 5 °C for 1 h, 75 % of females survived. RCH could also be induced by acclimatization at 30 °C for 2 h or anoxia (oxygen-free nitrogen) for 1-2 h. All immature stages showed enhanced survival when acclimatized at 5 °C for 2 h before exposure to -10 °C. Acclimatization at 30 °C induced RCH only in eggs and deutonymphs, and anoxia was effective for eggs, larvae, and deutonymphs. The variability among immature stages may be attributed to the cost associated with the acclimatization treatments. Our findings suggest that RCH may promote the survival of N. californicus during unexpected changes in temperatures, and can be an important feature particularly when this natural enemy is introduced to non-native environments.

Listening to German Native and Non-native Speakers: An Evaluation of Students’ Comprehension

Acquiring the German language in a non-native environment is a challenge to the students in UKM because the surroundings do not promote a conducive atmosphere for the students to communicate in the language. The students rely solely on their time in class to practice the four skills: reading, writing, listening and speaking. One of the most problematic skills to acquire is listening as the students are exposed to native German speakers only from the listening CD accompanying the text book ‘Studio D’. The previous research conducted by the instructor revealed that the students have difficulties in listening to native German speakers. However, the instructor could not determine whether articulation and accent of a native speaker, content difficulty or effect of background noise was the main factor leading to the problem. Thus, this research aims to evaluate the ability of the students to understand the dialogues spoken by native and non-native German speakers. For this research, authentic recordings of native and non-native speakers speaking were used as listening material. Students were divided into two groups: the first group listened to dialogues by native speakers and the second group listened to the same dialogue by non-native speakers. The students were then asked to answer multiple-choice and open task questions corresponding to the dialogues. It was found that the students who listened to the dialogues by non-native speakers performed slightly better. This suggests that the students‟ comprehension does not rely solely on native or non-native speakers but there are other contributing factors like contents and type of questions.

The Adaptation of English Consonants by Efik Learners of English

One of the linguistic outcomes of the sustained contact of a target language (L2) with a source language (L1) in the course of history is the adaptation and integration of loanwords from the former into the lexicon of the latter. This paper discusses the phonological strategies and parameters for the adaptation of English consonants (which mainly affect nouns) into Efik. The paper discusses the factors that are responsible for borrowing and convergence as well as the linguistic consequences of loanwords in the Efik expanded vocabulary. We submit that though the pattern of borrowing is tailored to agree with the phonological system of the source language, some of the changes are however, as a result of indigenous innovations or prosodic patterns. We argue in this paper that target-source language contact phenomenon is an important source of lexical enrichment of the target language, which has expanded its functional domains to cope with modern challenges. The paper considers the implication of the study for the English language teaching and learning classroom in the Efik non-native environment.