Many a slip: dissecting the causes of reproductive isolation in two species of Tegenaria spiders (Agelenidae)

Key to our understanding of the mechanisms underlying the process of speciation is the determination of the nature of the barriers to gene flow between related taxa. Species that show zero gene flow in sympatry or parapatry are of little use in this respect. In the present study, we used two closely‐related species of large house spider, Tegenaria saeva and Tegenaria gigantea, which hybridize to a limited extent along a natural contact zone in southern Britain. The species are apparently indistinguishable with respect to habitat utilization and phenology. Laboratory crosses using individuals from both allopatric and parapatric populations suggest that, although male and female courtship, as well as web and cuticular‐borne pheromones, are conserved between the species, mechanical difficulties are experienced during interspecific copulation. Copulation bouts are, on average, significantly shorter during interspecific matings because of these difficulties, and are probably not sufficiently long for effective sperm transfer to take place. In the two cases of successful interspecific crossing, and in subsequent F₁ and backcross generations, there are few indications of differential fertility, fecundity or viability, suggesting little post‐zygotic incompatibility. The high success rate of crosses between F₁ hybrids and both parental species underlines the principally mechanical barrier to gene flow between these taxa. Once this is breached, there appears to be little impediment to continuing introgression, which could, in some geographical areas at least, ultimately lead to the fusion of the two species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 355–367.     

Assessment of Anthropogenic Influence on Heavy Metals Contamination in the Aquatic Ecosystem Components: Water,Sediment, and Fish

Heavy metals (Pb, Cd, Ni, Cr, Cu, Zn, Mn, and As) concentration was investigated in the industrial effluents, water, sediment, and fish samples collected around the Dhaka Export Processing Zone, Savar, Bangladesh, to evaluate the level of contamination. The metals concentration in the industrial effluents of DEPZ and in the water samples of Dhalaibeel (lowland cum lake) and Bangshi River were significantly higher compared to the guideline values for industrial effluents and for drinking water (WHO and USEPA), respectively. The sedimentary metal concentrations were found to be lower than the respective probable effect concentrations (PECs) following the sediment quality guidelines. Furthermore, in comparison with the fish standards, the studied fish species were not found to be contaminated by heavy metals. Principal component analysis and cluster analysis demonstrated that the wastewater from the numerous industries and the domestic sewages around the DEPZ might have a possible impact on heavy metals contamination in the study area. The Pearson correlation analysis showed significant correlations (p < 0.01 and p < 0.05) between most of the metals in the samples of effluents, water, sediments, and fish muscles. The percentage enrichment factor (EF%) and geo-accumulation index () were followed to evaluate metal contamination in the sediment samples. Dhalaibeel sediment was maximally enriched for Cr (53.55%) and Bangshi River sediment for Zn (54.37%). The geo-accumulation index values for the sediment samples were less than zero, indicating that the sediment samples were free from contamination. This study could be used as a model study to assess the impact of anthropogenic activities on heavy metals contamination in aquatic ecosystems.     

Genome sequencing and comparative analysis of three Chlamydia pecorum strains associated with different pathogenic outcomes

Background

Chlamydia pecorum is the causative agent of a number of acute diseases, but most often causes persistent, subclinical infection in ruminants, swine and birds. In this study, the genome sequences of three C. pecorum strains isolated from the faeces of a sheep with inapparent enteric infection (strain W73), from the synovial fluid of a sheep with polyarthritis (strain P787) and from a cervical swab taken from a cow with metritis (strain PV3056/3) were determined using Illumina/Solexa and Roche 454 genome sequencing.

Results

Gene order and synteny was almost identical between C. pecorum strains and C. psittaci. Differences between C. pecorum and other chlamydiae occurred at a number of loci, including the plasticity zone, which contained a MAC/perforin domain protein, two copies of a >3400 amino acid putative cytotoxin gene and four (PV3056/3) or five (P787 and W73) genes encoding phospholipase D. Chlamydia pecorum contains an almost intact tryptophan biosynthesis operon encoding trpABCDFR and has the ability to sequester kynurenine from its host, however it lacks the genes folA, folKP and folB required for folate metabolism found in other chlamydiae. A total of 15 polymorphic membrane proteins were identified, belonging to six pmp families. Strains possess an intact type III secretion system composed of 18 structural genes and accessory proteins, however a number of putative inc effector proteins widely distributed in chlamydiae are absent from C. pecorum. Two genes encoding the hypothetical protein ORF663 and IncA contain variable numbers of repeat sequences that could be associated with persistence of infection.

Conclusions

Genome sequencing of three C. pecorum strains, originating from animals with different disease manifestations, has identified differences in ORF663 and pseudogene content between strains and has identified genes and metabolic traits that may influence intracellular survival, pathogenicity and evasion of the host immune system.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-23) contains supplementary material, which is available to authorized users.     

Bioinformatic analysis of ciliary transition zone proteins reveals insights into the evolution of ciliopathy networks

Background

Cilia are critical for diverse functions, from motility to signal transduction, and ciliary dysfunction causes inherited diseases termed ciliopathies. Several ciliopathy proteins influence developmental signalling and aberrant signalling explains many ciliopathy phenotypes. Ciliary compartmentalisation is essential for function, and the transition zone (TZ), found at the proximal end of the cilium, has recently emerged as a key player in regulating this process. Ciliary compartmentalisation is linked to two protein complexes, the MKS and NPHP complexes, at the TZ that consist largely of ciliopathy proteins, leading to the hypothesis that ciliopathy proteins affect signalling by regulating ciliary content. However, there is no consensus on complex composition, formation, or the contribution of each component.

Results

Using bioinformatics, we examined the evolutionary patterns of TZ complex proteins across the extant eukaryotic supergroups, in both ciliated and non-ciliated organisms. We show that TZ complex proteins are restricted to the proteomes of ciliated organisms and identify a core conserved group (TMEM67, CC2D2A, B9D1, B9D2, AHI1 and a single TCTN, plus perhaps MKS1) which are present in >50% of all ciliate/flagellate organisms analysed in each supergroup. The smaller NPHP complex apparently evolved later than the larger MKS complex; this result may explain why RPGRIP1L, which forms the linker between the two complexes, is not one of the core conserved proteins. We also uncovered a striking correlation between lack of TZ proteins in non-seed land plants and loss of TZ-specific ciliary Y-links that link microtubule doublets to the membrane, consistent with the interpretation that these proteins are structural components of Y-links, or regulators of their formation.

Conclusions

This bioinformatic analysis represents the first systematic analysis of the cohort of TZ complex proteins across eukaryotic evolution. Given the near-ubiquity of only 6 proteins across ciliated eukaryotes, we propose that the MKS complex represents a dynamic complex built around these 6 proteins and implicated in Y-link formation and ciliary permeability.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-531) contains supplementary material, which is available to authorized users.     

New Insights into an Old Organelle: Meeting Report on Biology of Cilia and Flagella

The rising interest of the scientific community in cilia biology was evident from the fact that registration for the third FASEB conference on ‘The Biology of Cilia and Flagella’ closed out before the early bird deadline. Cilia and flagella are organelles of profound medical importance; defects in their structure or function result in a plethora of human diseases called ciliopathies. 240 clinicians and basic scientists from around the world gathered from 23 June 2013 to 28 June 2013 at Sheraton at the Falls, Niagara Falls, NY to present and discuss their research on this intensely studied subcellular structure. The meeting was organized by Gregory Pazour (University of Massachusetts Medical School), Bradley Yoder (University of Alabama‐Birmingham), and Maureen Barr (Rutgers University) and was sponsored by the Federation of American Societies for Experimental Biology (FASEB). Here, we report highlights, points of discussion, and emerging themes from this exciting meeting.     

Human Health Risk of Metals in Drinking-Water Source Areas from a Forest Zone after Long-Term Excessive Deforestation

The concentrations of 10 metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Se, Zn) were determined in drinking water in Khingan, China, a forest zone after long-term excessive deforestation. These metals’ concentrations in water exceeded background values of metals in some other regions of the world, indicating that there were other metal sources contributing to such high levels of metals in Khingan. Arsenic was the only metal whose concentration exceeded the maximum levels allowed in drinking water. Principal component analysis showed that As, Cd, Cu, and Se originated from anthropogenic sources and exhibited significantly high concentrations in north Khingan, while Fe and Mn derived from natural formation and showed significantly high concentrations in central Khingan. Health risks from metals were evaluated by a model recommended by the U.S. Environmental Protection Agency. Ingestion was the predominant pathway of exposure to metals in water for local residents. Arsenic was also the only metal causing both noncarcinogenic hazard and carcinogenic risk in Khingan. The high risks occurred mainly in north Khingan and are associated with coal combustion. This study indicates that long-term excessive deforestation may increase As concentration considerably in drinking water and then pose health risks to local residents.     

大理洱海湖滨带鸟类多样性

洱海地处云南西部,是中国西部候鸟迁徙时的重要停息地和越冬地,但其湖滨带鸟类组成与季节变化尚无专门研究。作者于2011年1月(冬季)、3和4月(春季)、7月(夏季)、10和11月(秋季)采用样线法对洱海湖滨带的鸟类多样性进行了调查,在洱海西岸湖滨带共设4条调查样线,总长度48.2 km,冬夏季节各进行2 d共4次调查,春秋各进行4 d共8次调查。共记录到鸟类13目38科115种,其中有国家Ⅱ级重点保护鸟类7种;留鸟61种,夏候鸟7种,冬候鸟39种,旅鸟8种;按生态类群分,有游禽19种,涉禽22种,猛禽7种,陆禽3种,攀禽8种,鸣禽56种。研究结果表明,秋季的鸟类物种数及多样性指数最高,夏季均匀性指数最高。5类生境中,树林灌丛生境的鸟类多样性和均匀性最高;近岸水域鸟类个体数量最多。依据调查结果,建议沿环湖公路营造更多树林,在适宜地点建造滩涂,将有利于鸟类栖息觅食。     

红树林生态系统中不同生境不同深度土壤的可培养真菌的多样性

【目的】了解八门湾红树林生态系统中不同生境(潮间带、海洋到红树区的过渡带、海桑红树区)和不同深度土壤的可培养真菌的多样性。【方法】采用稀释涂布平板法分离土壤中的真菌,利用形态学观察和ITS rDNA序列分析技术研究可培养真菌的表观和遗传多样性。【结果】从八门湾红树林生态系统的3个不同生境中分离到257株真菌,分别属于21属28种,其中青霉属(Penicillium)、曲霉属(Aspergillus)和木霉属(Trichoderma)为优势类群。来自不同生境或者同一生境不同采样深度的土壤真菌种类组成不同,并且有些真菌类群只出现在特定的样品中。从空间角度看,红树区土壤样品的真菌多样性高于其他两个生境的土壤样品;从垂直角度看,潮间带和过渡带的表层土壤样品的真菌多样性高于深层土壤样品,而红树区的深层土壤样品真菌多样性高于表层土壤样品。【结论】八门湾红树林生态系统中的可培养真菌资源丰富,种类多样性较高,但不同生境或不同深度的可培养真菌分布存在较大的差异。这些结果揭示了红树林土壤中可培养真菌的生态分布特点,也为红树林真菌资源的开发利用提供了基础的背景资料。     

Effects of woody debris and the supply of terrestrial invertebrates on the diet and growth of brown trout (Salmo trutta) in a boreal stream

相似文献   

Shifts in thermoregulatory strategy during ontogeny in harp seals (Pagophilus groenlandicus)

Heat balance can be difficult for young and/or small animals in polar regions because environmental conditions in combination with small body size or physiological immaturity can increase heat loss. We investigated how thermoregulatory patterns change with ontogeny in 5 age classes of harp seal (Pagophilus groenlandicus) from birth to post-molt to further understand the timing of thermoregulatory development in relation to their potential vulnerability to ongoing fluctuations in the extent and stability of Arctic pack ice. We measured changes in the amount, conductivity, and resistance of the seal pups׳ insulative layers (blubber and fur), the potential for endogenous heat-generation by shivering (muscle enzyme activity), and nonshivering thermogenesis (NST; brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression and mitochondrial density). There was no significant difference in blubber conductivity among age classes, though the amount of blubber insulation significantly increased from birth to weaning. Pelage conductivity was low (0.12±0.01 W m⁻¹ °C⁻¹) except in 9-day old pups (0.40±0.08 W m⁻¹ °C⁻¹); the significantly higher conductivity may signal the beginning of the molt, and this age group may be the most vulnerable to early water entry. Citrate synthase activity significantly increased (49.68±3.26 to 75.08±3.52 μmol min⁻¹ g wet weight⁻¹) in the muscle; however it is unlikely that increasing a single enzyme greatly impacts heat generation. BAT of younger pups contained UCP1, though expression and mitochondrial density quickly declined, and the ability of pups to produce heat via NST was lost by weaning. While total thermal resistance did not differ, neonatal and early nursing animals gained the majority of their thermal resistance from lanugo (82.5±0.03%); however, lanugo is not insulative when wet, and NST may be important to maintain euthermia and dry the coat if early immersion in water occurs. By late nursing, blubber seems sufficient as insulation (75.87±0.01% of resistance after 4 weeks), but high conductivity of fur may be responsible for retention of UCP1 expression. Weaned animals rely on blubber insulation, and no longer need NST, as wetted fur is no longer a threat to euthermia.