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This paper describes the plant communities of two oligotrophic karstic rivers with a slight anthropogenic influence — the Trebi?at and the Li?tica — in South Bosnia and Herzegovina, their sinecology, and the relationship between vegetation and plant species and environmental parameters. According to 87 relevés, a total of 26 plant associations, using Braun-Blanquet methods, were found in the rivers and nearby surveyed area. Only nine associations were common to both rivers. Eight associations were recorded for the territory of Bosnia and Herzegovina for the first time. Associations from both rivers differed according to following parameters measured at the sampling site: water temperature, distance from the mouth (river kilometers), river width, water depth, flow, pH and slope. There were no differences in nutrient concentrations among the associations. According to Canonical Correspondence Analysis (CCA), three environmental variables out of the 11 initially considered were retained as being related to plant distribution. The first two axes explained 56.8% and 35.2% of variance of species-environment relationship in the Trebi?at and Li?tica rivers, respectively. Water depth in the Trebi?at River, and pH and river kilometers in the Li?tica River were found to be the most influential, while nutrients and other physico-chemical parameters were not significant in either river. Water depth vector was identified as an underlying environmental factor determining distribution of Potamogeton lucens and Myriophyllum verticillatum (Potamion), and Nymphaea alba (Nymphaeion albae). According to in situ measurements of light intensity, the highest coefficients of light attenuation, radiance and reflection were found at a station with dense populations of Potamogeton lucens and Nuphar luteum (Potametum lucentis). The vegetation and floristic value of the rivers is discussed as a basis for biodiversity conservation programmes and evaluating the state of these ecosystems in the future.  相似文献   
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A gene encoding endochitinase from Trichoderma virens UKM-1 was cloned and expressed in E. coli BL21 (DE3). Both the endochitinase gene and its cDNA sequences were obtained. The endochitinase gene encodes 430 amino acids from an open reading frame comprising of 1,690 bp nucleotide sequence with three introns. The endochitinase was expressed as soluble and active enzyme at 20°C when induced with 1 mM IPTG. Maximum activity was observed at 4 h of post-induction time. SDS-PAGE showed that the purified endochitinase exhibited a single band with molecular weight of 42 kDa. Biochemical characterization of the enzyme displayed a near neutral pH characteristic with an optimum pH at 6.0 and optimum temperature at 50°C. The enzyme is stable between pH 3.0–7.0 and is able to retain its activity from 30 to 60°C. The presence of Mg2+ and Ca2+ ions increased the enzyme activity up to 20%. The purified enzyme has a strong affinity towards colloidal chitin and low effect on ethyl cellulose and D-cellubiose which are non-chitin related substrates. HPLC analysis from the chitin hydrolysis showed the release of (GlcNAc)3, (GlcNAc)2 and GlcNAc, in which (GlcNAc)2 was the main product.  相似文献   
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Tissue engineering, an immensely important field in contemporary clinical practices, aims at the repair or replacement of damaged tissues. The mathematical model proposed herein shows the distribution and growth of cells in their characteristic time in a 3D scaffold model. This study contributes to the progress of simulation techniques in static and dynamic cultures of bone tissue. Brinkman, nutrient transport, and cell growth equations are brought together to quantify the growth behavior of cells. However, when a static culture is being studied, the Brinkman equation is eliminated. The model was validated by experimental cell culture using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay and scanning electron microscopy. Then, static and dynamic cultures were compared to assess the cell density and cell distribution in the scaffold. Cell counting after 21 days of cell culture showed that the number of cells increased 42‐fold in static and 53.5‐fold in dynamic cultures, which was in good agreement with our model estimations (37‐fold increase in the number of cells in static and 49‐fold increase in dynamic cultures). In conclusion, our mathematical model could predict cell distribution and growth in the scaffold.  相似文献   
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Most recorded extinctions have occurred on oceanic islands, mainly as a result of introduced mammalian predators. The impact of introduced non-mammalian competitors, however, is poorly understood. The house gecko, Hemidactylus frenatus, is one of the most successful invasive reptiles and has been implicated in the decline of endemic geckos and other taxa on a number of tropical and subtropical islands. We investigated the patterns of niche utilization between the house gecko and endemic ornate day gecko, Phelsuma ornata, in Mauritius, two species which were not believed to compete because they had different diel activity periods. The dietary and temporal niche partitioning of the two species were examined in relation to seasonal invertebrate prey abundance for three seasons. Dietary overlap between the two species was least when prey abundance was lowest and temporal overlap in activity greatest. Exploitative competition was therefore inferred, whereby changes in dietary overlap were attributed to shifts in prey selection by the day, but not the house, gecko, which was hypothesized to deplete prey. The compensatory response of the day gecko may have been to increase its tendency for cannibalism, such that the smaller house gecko was indirectly responsible for population reduction of its larger competitor. This is the first study to show how an invasive nocturnal gecko may be affecting a predominantly diurnal species.  相似文献   
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  1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
  2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
  3. We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
  4. We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
  5. Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.
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Mango malformation has become the most important global disease on mango. Fusarium species previously associated with this disease include F. mangiferae, F. mexicanum, F. sterilihyphosum, F. proliferatum, F. subglutinans and F. tupiense. A few strains of F. proliferatum have been reported from Malaysia, but in this study, we report the results of more extensive sampling. The recovered strains were evaluated with morphology, mating tester strain cross‐fertility, amplified fragment length polymorphisms (AFLPs), and partial DNA sequences of the genes encoding translation elongation factor 1‐α (tef‐1α) and β‐tubulin (tub‐2). Amongst the 43 strains evaluated, three species were identified – F. proliferatum, F. mangiferae and F. subglutinans – with F. proliferatum being the most frequent (69%). None of the Fusarium species that appear to originate in the Americas were recovered in Malaysia, which suggests special measures may be warranted to keep these species from entering the country.  相似文献   
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We assessed the variability of chloroplast DNA sequences in populations of the dipterocarp forest tree, Shorea curtisii. This species is widely distributed in hill and coastal hill dipterocarp forests of the Malay Peninsula, whereas isolated populations are found in the coastal hills of north Borneo. Two chloroplast DNA regions (1555 bp of trnHpsbAtrnK and 925 bp of trnLtrnF) were sequenced from 123 individuals collected from six Malay Peninsula and two Bornean populations. There were 15 chloroplast haplotypes derived from 16 polymorphic sites. A haplotype network revealed two distinct haplogroups that correlate with two geographic regions, the Malay Peninsula and Borneo. These two haplogroups differed by a number of mutations, and no haplotypes were shared between populations from the different geographic regions. This suggests an ancient diversification of these haplogroups, and that long‐distance seed dispersal was unlikely to have occurred during the Pleistocene when the Sunda Shelf was a contiguous landmass. Phylogenetic analysis of the haplotypes together with those found in other Shorea species showed that two haplogroups in S. curtisii appear in different positions of the phylogenetic tree. This could be explained by the persistence of ancestral polymorphisms or by ancient chloroplast capture. Low levels of genetic differentiation were found between populations within each geographic region. Signature of a bottleneck followed by demographic expansion was detected in the Malay Peninsula haplogroup. The presence of two distinct evolutionary lineages in the different regions suggests that they should be managed independently to conserve the major sources of genetic diversity in S. curtisii.  相似文献   
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