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41.
Spatiotemporal relationship between adult census size and genetic population size across a wide population size gradient
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Adult census population size (N) and effective number of breeders (Nb) are highly relevant for designing effective conservation strategies. Both parameters are often challenging to quantify, however, making it of interest to determine whether one parameter can be generalized from the other. Yet, the spatiotemporal relationship between N and Nb has not been well characterized empirically in many taxa. We analysed this relationship for 5–7 consecutive years in twelve brook trout populations varying greatly in N (49‐10032) and Nb (3‐567) and identified major environmental variables affecting the two parameters. N or habitat size alone explained 47–57% of the variance in Nb, and Nb was strongly correlated with effective population size. The ratio Nb/N ranged from 0.01 to 0.45 and increased at small N or following an annual decrease in N, suggesting density‐dependent constraints on Nb. We found no evidence for a consistent, directional difference between variability in Nb and/or Nb/N among small and large populations; however, small populations had more varying temporal variability in Nb/N ratios than large populations. Finally, Nb and Nb/N were 2.5‐ and 2.3‐fold more variable among populations than temporally within populations. Our results demonstrate a clear linkage between demographic and evolutionary parameters, suggesting that Nb could be used to approximate N (or vice versa) in natural populations. Nevertheless, using one variable to infer the other to monitor trends within populations is less recommended, perhaps even less so in small populations given their less predictable Nb vs. N dynamics. 相似文献
42.
The social relationships between the members of a family consisting of eight captive common marmosets (Callithrix jacchus) are here examined, as well as the participation of individual family members in infant carrying and defensive behaviour
against non-related intruders (adolescent males). Within the social relationships, a clear division of the family into three
subgroups (parents, adult offspring, non-adult offspring) could be determined, whereby the adult offspring, especially with
respect to the parents, occupy a peripheral position. In the types of cooperative behaviour examined here, substantial participation
in infant carrying could be observed in only four family members (parents, adult son, one subadult daughter), and in defence
against intruders in only two family members (adult son, one subadult daughter). Participation in infant carrying remained
stable throughout the study period. Conversely, individual changes in participation in defence against intruders could be
determined, dependent upon the presence of infants carried. The advantages and disadvantages of social substructuring observed
are discussed here, in particular the peripheral position of adult offspring, possible connections in individually varied
participation in cooperative behaviour, and possible regulative mechanisms. In view of past studies on cooperative behaviour
among marmosets, it is here presumed that pronounced individual differences result from a division of labour within the family
with respect to various aspects of cooperative behaviour. 相似文献
43.
Ahnut Burchard 《Journal of mathematical biology》1994,32(5):465-489
We discuss a system of ordinary differential equations that can be used to model the interspecies hydrogen transfer common in anaerobic degradation of organic matter. The mutualistic character of the interaction is not modeled explicitly but emerges as a consequence of the kinetics of nutrient uptake. Using monotonicity assumptions on the reaction terms, we characterise the equilibria and their stability and demonstrate two-parameter bifurcation of periodic solutions near singularities of the Bogdanov-Takens type. We have persistence and extinction results in a wide range of parameter values. Finally, we give some conditions for equivalence and non-equivalence to a cooperative system and compare to related models. 相似文献
44.
Edward Walker Jeffrey P. Gardner Vladimir Litvin Evan L. Turner 《Cluster computing》2007,10(3):339-350
We describe a system for creating personal clusters in user-space to support the submission and management of thousands of
compute-intensive serial jobs to the network-connected compute resources on the NSF TeraGrid. The system implements a robust
infrastructure that submits and manages job proxies across a distributed computing environment. These job proxies contribute
resources to personal clusters created dynamically for a user on-demand. The personal clusters then adapt to the prevailing
job load conditions at the distributed sites by migrating job proxies to sites expected to provide resources more quickly.
Furthermore, the system allows multiple instances of these personal clusters to be created as containers for individual scientific
experiments, allowing the submission environment to be customized for each instance. The version of the system described in
this paper allows users to build large personal Condor and Sun Grid Engine clusters on the TeraGrid. Users then manage their
scientific jobs, within each personal cluster, with a single uniform interface using the feature-rich functionality found
in these job management environments.
相似文献
Evan L. TurnerEmail: |
45.
Huey W. Huang 《生物化学与生物物理学报:生物膜》2006,1758(9):1292-1302
Based on very extensive studies on four peptides (alamethicin, melittin, magainin and protegrin), we propose a mechanism to explain the cooperativity exhibited by the activities of antimicrobial peptides, namely, a non-linear concentration dependence characterized by a threshold and a rapid rise to saturation as the concentration exceeds the threshold. We first review the structural basis of the mechanism. Experiments showed that peptide binding to lipid bilayers creates two distinct states depending on the bound-peptide to lipid ratio P/L. For P/L below a threshold P/L*, all of the peptide molecules are in the S state that has the following characteristics: (1) there are no pores in the membrane, (2) the axes of helical peptides are oriented parallel to the plane of membrane, and (3) the peptide causes membrane thinning in proportion to P/L. As P/L increases above P/L*, essentially all of the excessive peptide molecules occupy the I state that has the following characteristics: (1) transmembrane pores are detected in the membrane, (2) the axes of helical peptides are perpendicular to the plane of membrane, (3) the membrane thickness remains constant for P/L ≥ P/L*. The free energy based on these two states agrees with the data quantitatively. The free energy also explains why lipids of positive curvature (lysoPC) facilitate and lipids of negative curvature (PE) inhibit pore formation. 相似文献
46.
This study examines factors affecting androgen and cortisol levels in wild, male golden lion tamarins (Leontopithecus rosalia). Golden lion tamarins are a cooperatively breeding species in which groups often contain two potentially breeding males. Brothers frequently emigrate together and develop a clear dominance hierarchy, but interactions between them are primarily affiliative. Duos in which the males are not related are less stable. In addition, reproductive skew theory predicts that dominant males will be less likely to share reproduction with related subordinates. As such, we predicted that both androgens and cortisol would be higher in subordinate males unrelated to the dominant male. We also predicted that androgens in breeding males would be higher during the mating season than the birth/infant care season, as per Wingfield's "challenge hypothesis" (1990). Fecal samples were collected from 24 males in 14 social groups and assayed by enzyme immunoassay. Androgen levels were higher in breeding males during the mating season, thus supporting the challenge hypothesis. However, while subordinate males unrelated to the dominant male had significantly lower androgens than any other group, cortisol levels were not correspondingly higher. These results suggest that unrelated subordinate males show measurable reproductive suppression and may use strategies such as infantilization to avert aggression from dominant males. 相似文献
47.
Taghdir M Naderi-Manesh H 《Biochemical and biophysical research communications》2006,351(4):1037-1042
We decided to investigate the influence of the presence of disulfide bonds on the pattern of force distribution in the functional site of scorpion toxin BMK M1 in its functional state. Therefore, a series of short time molecular dynamics (MD) simulations were performed on this toxin in the native state and disulfide bond broken states. The comparison of disulfide bond broken states with the native state showed that the electrostatic potential energy of important functional residues in the reverse turn and C-terminal regions were modulated by the cooperative effect of all disulfide bonds in the molecule. Furthermore, our results revealed that disulfide bonds also play a cooperative role in modulating (1) the amplitude of the fluctuations of the functional segments and (2) the correlation of motions between important functional residue pairs in this toxin. Therefore, we can conclude that the disulfide bonds have cooperation to adjust the pattern of force distribution in the functional site of this toxin in its functional state. 相似文献
48.
Næss Marius Warg Fauchald Per Tveraa Torkild 《Human ecology: an interdisciplinary journal》2009,37(2):193-211
Human Ecology - While there is a general assumption that labor has a positive effect on pastoral production, studies that have tried to quantify this relationship have found no effects. This is... 相似文献
49.
We studied the effects of body mass, status (resident or migratory) and diet on the breeding elevation range and timing of
reproduction of the birds in the Trans-Himalayan region of Ladakh, northwestern India. Most of breeding birds of Ladakh are
Palearctic or breed at high elevations in the mountains. There is a small proportion of Oriental species, and no bird is endemic
to this region. We found that heavier birds tended to start their egg-laying earlier than lighter ones. Since body mass is
related to the length of incubation and nesting periods, it would appear that one result of this phenomenon is that the time
of peak demand for food for most birds coincides with peak food abundance in summer. Status affected the elevation of the
breeding range, with resident birds tending to breed at higher elevations than summer visitors. Residents and summer breeders
also differed significantly in their diet composition, with the former feeding mainly on plants and seeds, and the latter
feeding on molluscs, insects and worms. 相似文献
50.
Constrained optimization problems arise in a wide variety of scientific and engineering applications. Since several single
recurrent neural networks when applied to solve constrained optimization problems for real-time engineering applications have
shown some limitations, cooperative recurrent neural network approaches have been developed to overcome drawbacks of these
single recurrent neural networks. This paper surveys in details work on cooperative recurrent neural networks for solving
constrained optimization problems and their engineering applications, and points out their standing models from viewpoint
of both convergence to the optimal solution and model complexity. We provide examples and comparisons to shown advantages
of these models in the given applications. 相似文献