Turnbull LA  Rees M  Purves DW 《Ecology letters》2008,11(10):1037-1046

Equalising trade-offs, such as seed mass vs. number, have been invoked to reconcile neutral theory with observed differences between species. This is an appealing explanation for the dramatic seed size variation seen within guilds of otherwise similar plants: under size-symmetric competition, where resource capture is proportional to mass, the outcome of competition should be insensitive to whether species produce many small seeds or few large ones. However, under this assumption, stochastic variation in seed rain leads to exclusion of all but the smallest-seeded species. Thus stochasticity in seed arrivals, a process that was previously thought to generate drift, instead results in deterministic competitive exclusion. A neutral outcome is possible under one special case of a more general equalising framework, where seed mass affects survival but not competition. Further exploration of the feasibility of neutral trade-offs is needed to understand the respective roles of neutrality and niche structure in community dynamics.  相似文献   

Structure of a dominant-negative helix-loop-helix transcriptional regulator suggests mechanisms of autoinhibition     

Ishii R  Isogaya K  Seto A  Koinuma D  Watanabe Y  Arisaka F  Yaguchi S  Ikushima H  Dohmae N  Miyazono K  Miyazawa K  Ishitani R  Nureki O 《The EMBO journal》2012,31(11):2541-2552

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Helmut Hillebrand 《Journal of phycology》2009,45(4):798-806

Grazer control of periphyton biomass has been addressed in numerous experimental studies in all kinds of aquatic habitats. In this meta‐analysis, the results of 865 experiments are quantitatively synthesized in order to address the following questions: (i) Do lotic, lentic, and marine ecosystems differ in their degree of grazer control of periphyton biomass? (ii) Which environmental variables affect the degree of grazer control? (iii) How much does the result of these experiments depend on facets of experimental design? Across all ecosystems, the grazers removed on average 59% of the periphyton biomass, with grazing being significantly stronger for laboratory (65%) than for field (56%) experiments. Neither field nor lab experiments showed a significant difference among lotic, lentic, and coastal habitats. Among different taxonomic consumer groups, crustaceans (amphipods and isopods) and trichopteran larvae removed the highest proportion of periphyton biomass. Grazer effects increased with increasing algal biomass, with decreasing resource availability and with increasing temperature, especially in field experiments. Grazer effects also increased with increasing total grazer biomass in field experiments but showed the opposite trend in lab experiments, indicating a tendency toward overcrowded lab experiments. Other aspects of experimental design, such as cage type, size, and duration of the study, strongly affected the outcome of the experiments, suggesting that much care has to be placed on the choice of experimental design.  相似文献   

    

Lodeiro P  Cordero B  Grille Z  Herrero R  Sastre de Vicente ME 《Biotechnology and bioengineering》2004,88(2):237-247

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Guntur KV  Velasquez D  Chadwell L  Carroll C  Weintraub S  Cassill JA  Renthal R 《Archives of insect biochemistry and physiology》2004,57(3):101-110

Antennal proteins of the male fire ant (Solenopsis invicta) were analyzed by two-dimensional gel electrophoresis, with the objective of identifying pheromone-binding proteins, which have not previously been found in ant antennae. The major low-molecular weight protein found in the male fire ant antenna was subjected to Edman degradation to determine the N-terminal amino acid sequence. Degenerate PCR primers based on this sequence were used to obtain a cDNA sequence corresponding to the full-length protein sequence. In-gel trypsin digestion followed by MALDI-TOF mass spectrometry and HPLC-ESI/MS/MS demonstrated that the protein gel spot contained only the protein corresponding to the cDNA sequence obtained by PCR. The sequence is similar to apolipophorin-III, an exchangeable lipid-binding protein. Fire ant apolipophorin-III is expressed in the antenna as well as the head, thorax and abdomen.  相似文献   

    

Joannes Van Cann  Esa Koskela  Tapio Mappes  Anne‐Mari Mikkonen  Mikael Mokkonen  Phillip C. Watts 《Journal of evolutionary biology》2019,32(10):1141-1151

Intergenerational fitness effects on offspring due to the early life of the parent are well studied from the standpoint of the maternal environment, but intergenerational effects owing to the paternal early life environment are often overlooked. Nonetheless, recent laboratory studies in mammals and ecologically relevant studies in invertebrates predict that paternal effects can have a major impact on the offspring's phenotype. These nongenetic, environment‐dependent paternal effects provide a mechanism for fathers to transmit environmental information to their offspring and could allow rapid adaptation. We used the bank vole Myodes glareolus, a wild rodent species with no paternal care, to test the hypothesis that a high population density environment in the early life of fathers can affect traits associated with offspring fitness. We show that the protein content in the diet and/or social environment experienced during the father's early life (prenatal and weaning) influence the phenotype and survival of his offspring and may indicate adaptation to density‐dependent costs. Furthermore, we show that experiencing multiple environmental factors during the paternal early life can lead to a different outcome on the offspring phenotype than stimulated by experience of a single environmental factor, highlighting the need to study developmental experiences in tandem rather than independent of each other.  相似文献   

    

Muriel Dietrich  Florent Kempf  Elena Gómez‐Díaz  Alexander S. Kitaysky  J. Mark Hipfner  Thierry Boulinier  Karen D. McCoy 《Journal of Biogeography》2012,39(3):545-555

Aim Parasites with global distributions and wide host spectra provide excellent models for exploring the factors that drive parasite diversification. Here, we tested the relative force of host and geography in shaping population structure of a widely distributed and common ectoparasite of colonial seabirds, the tick Ixodes uriae. Location Two natural geographic replicates of the system: numerous seabird colonies of the North Pacific and North Atlantic Ocean basins. Methods Using eight microsatellite markers and tick samples from a suite of multi‐specific seabird colonies, we examined tick population structure in the North Pacific and compare patterns of diversity and structure to those in the Atlantic basin. Analyses included population genetic estimations of diversity and population differentiation, exploratory multivariate analyses, and Bayesian clustering approaches. These different analyses explicitly took into account both the geographic distance among colonies and host use by the tick. Results Overall, little geographic structure was observed among Pacific tick populations. However, host‐related genetic differentiation was evident, but was variable among host types and lower than in the North Atlantic. Main conclusions Tick population structure is concordant with the genetic structure observed in seabird host species within each ocean basin, where seabird populations tend to be less structured in the North Pacific than in the North Atlantic. Reduced tick genetic structure in the North Pacific suggests that host movement among colonies, and thus tick dispersal, is higher in this region. In addition to information on parasite diversity and gene flow, our findings raise interesting questions about the subtle ways that host behaviour, distribution and phylogeographic history shape the genetics of associated parasites across geographic landscapes.  相似文献   

The proteome of the phytopathogenic fungus Sclerotinia sclerotiorum     

Yajima W  Kav NN 《Proteomics》2006,6(22):5995-6007

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Miikka Pakkala  Anu Jylhsalmi  Ping Wu  Jari Leinonen  Ulf‐Hkan Stenman  Harri Santa  Jouko Vepslinen  Mikael Perkyl  Ale Nrvnen 《Journal of peptide science》2004,10(7):439-447

Prostate-specific antigen (PSA), a member of the kallikrein sub-group of the trypsin serine protease family, is a widely used marker for prostate cancer. Several sequences with specific binding to PSA have been identified by using phage display peptide libraries. The GST-fusion proteins of the characterized sequences have been shown to increase the enzyme activity of PSA to a synthetic substrate. The corresponding three cyclic synthetic analogues CVFTSNYAFC (A-1), CVFAHNYNYLVC (B-2) and CVAYCIEHHCWTC (C-4) have similar PSA promoting activity. Despite differences in the amino acid sequences, all three peptides bind to the same region of PSA. The conformation of the peptides was investigated by proton NMR spectroscopy. In addition, alanine replacement was used to characterize the prerequisites for binding. It is proposed that interactions with PSA are based on the aromatic and hydrophobic features of the amino acid side chains. Furthermore, it is suggested that peptides form beta-turn structures forced by cysteine bridges directing important aromatic side chains to the same side of the turn-structure.  相似文献   

    

Nandel FS  Khare B 《Biopolymers》2005,77(1):63-73

Conformational studies of the peptides constructed from achiral amino acid residues Aib and Delta(Z)Phe (I) Ac-Aib-Delta(Z)Phe-NHMe (II), and Ac-(Aib-Delta(Z)Phe)(3)-NHMe; peptides III-VI having L-Leu or D-Leu at either the N- or the C-terminal position and of peptides VII-X having Leu residues in different enantiomeric combinations at both the N- and the C-terminal positions in peptide II have been studied to design the peptide with the required helical sense. Peptide II, as expected, adopts degenerate left- and right-handed helical structures. It has been shown that the peptides IV and VI having D-Leu at either the N or the C terminus can be realized in the right-handed helical structure with the phi,psi values of -20 degrees and -60 degrees for the Aib/Delta(Z)Phe residues. L-Leu and D- Leu at both the terminals in peptides VII and VIII, respectively, have hardly any effect as both the left- and the right-handed structures are found to be degenerate. Peptides III and IX can be realized in right- and left-handed helical structures, respectively, in solvents of low polarity whereas peptides V and X are predicted to be in the right-handed helical structures stabilized by carbonyl-carbonyl interactions without the formation of hydrogen bonds. The conformational states with the phi,psi values of 0 degrees and -85 degrees in peptide V are characterized by rise per residue of 2.03 A, rotation per residue of 117.5 degrees , and 3.06 residues per turn. In all peptides having Leu residue at the N terminus, the methyl moiety of the acetyl group is involved in the CH/pi interactions with the Cepsilon--Cdelta edge of the aromatic ring of Delta(Z)Phe (3) and the amino group NH of Delta(Z)Phe is involved in the NH/pi interactions with its own aromatic ring. The CH(3) groups of the Aib residues are also involved in CH/pi interactions with the i + 1th and i + 3th Delta(Z)Phe's aromatic side chains.  相似文献