Distinguishing niche and neutral processes: issues in variation partitioning statistical methods and further perspectives

Variance partitioning methods, which are built upon multivariate statistics, have been widely applied in different taxa and habitats in community ecology. Here, I performed a literature review on the development and application of the methods, and then discussed the limitation of available methods and the difficulties involved in sampling schemes. The central goal of the work is then to propose some potential practical methods that might help to overcome different issues of traditional least-square-based regression modeling. A variety of regression models has been considered for comparison. In initial simulations, I identified that generalized additive model (GAM) has the highest accuracy to predict variation components. Therefore, I argued that other advanced regression techniques, including the GAM and related models, could be utilized in variation partitioning for better quantifying the aggregation scenarios of species distribution.Comment: 19 pages; 4 figure

Ecogeography of haplotype composition of Sagittaria trifolia L. (Alismataceae) : environment, space, vicariance and selective sweeps

In the present report, the relative influence of environment and space was evaluated for explaining the variation of haplotype composition of 42 populations of Sagittaria trifolia L. (Alismataceae) in China. The results showed that, neither environment nor space could explain current haplotype composition patterns of S. trifolia, and most variation in haplotype composition could not be explained. Vicariance was recognized to explain the pattern that most haplotypes (25 out of 27 ones) were rare, being found in only one or two populations of S. trifolia in China. Finally, an emerging selective sweep from increasing human activity and habitat destruction explained the dominance patterns of haplotypes 5 and 8 among populations of S. trifolia

Possibility Approach o Newsboy Problem

The newsboy problem, also known as news-vendor or the single-period problem is a well-known inventory management problem. Interest in such a problem has increased over the past 40 years partially because the increased dominance of service industrial for which newsboy problem is very applicable in both retailing and service organization. Also, the reduction in product life cycles makes newsboy problem more relevant. Many extensions have been made in last decade, such as different objects and utility function, different supplier pricing policies, different new-vendor pricing policies [2][3][4]. However, almost all of extensions have been made in the probabilistic framework, that is, the uncertainty of demand and supply is characterized by the probability distribution, and the objective function is used to maximizing the expected profit or probability measure of achieving a target profit. There are still some problems left. The one is for life-cycle short products, such as fashion goods, season presents, there is no data to be used for statistical analysis to predict the coming demand. The other is newsboy problem is a typical one-shoot decision problem so that maximizing the expected profit or probability measure seems less meaningful. It seems that possibility theory-based method is another alternative to deal with such kind of decision problem. In this paper the plausible information of demand is dharacterized by the possibility distribution and the optimal order is determined according to the possibilistic decision criteria

An Investigation and Reduction of Electro-Optical Noise in Tunable Diode Laser

A double FFT (DFFT) procedure is developed to reduce the effect of 1/f noise in the spectrum of Distribution FeedBack (DFB) tunable diode laser. Simulations and experimental results are preformed. An obvious effectiveness of the double FFT on the 1/f noise spectrum has been observed. The 1/f noise was monitored in the three terminals. A linear fitting of the 1/f was verified for Single FFT (SFFT) and (DFFT) to calculate the Frequency Exponent Factor (FEF) ? and the amplitude of 1/f noise. Keywords: Fast Fourier transformation, tunable diode laser, Double Fast Fourier Transfor

MBI: an R package for calculating multiple-site beta diversity indices

Beta diversity is one of most important features in community ecology. Indices for pairwise comparison of beta diversity have been extensively developed, but the ones specifically designed for multiple-site comparison of beta diversity are still limited. Currently, by compiling all the available metrics based on the previous literature, plus some new metrics developed in the present report, we made the calculation of these multiplesite beta-diversity statistics become ready for ecologists using R computing environment. An empirical study was present using 290 real-world presence/absence matrices. The results showed that (1) mean pairwise indices could be good surrogates for multiple-site indices in principle, except the mean pairwise richness different index; (2) most of the indices were highly correlated, as indicated by Pearson correlation and significance test. The new R package "MBI" for calculating multiple-site diversity indices could be downloaded from the http://cran.r-project.org/web/packages/MBI/