Niche overlap and ecological tolerance of non-marine Ostracoda in Turkey

We applied niche overlap indices to for the first time show possible correlational occurrences among 40 non-marine ostracod taxa from seven aquatic habitats (lakes, creeks, ponds, springs, ditches, pools, troughs) in Turkey. Ecological tolerance and optimum estimates of each species were calculated and compared to explain possible reasons for habitat utilization. Eleven species were found suitable for the application of these indices. Overlap ranges of five of the species were found suitable for five variables (pH, dissolved oxygen, water temperature, electrical conductivity, and elevation; P < 0.05). Heterocypris incongruens (Ramdohr, 1808) and H. salina (Brady, 1868) were the only two species with common overlap for all the five variables. These two species generally showed common resource-utilization curves for each of these variables along with relatively similar tolerance ranges. Complete overlap was only possible for some cosmoecious species when they displayed wide-tolerance ranges and low optimum estimates for different environmental variables. Results suggest that cosmopolitan species do not only have wide geographical distributions but tolerance ranges higher than other species. Such wide tolerance ranges seem to help species coinhabit with each other and elevate their co-occurrence probabilities in different types of habitats. Applying the first usage of overlap indices on ostracods and attempting to show the relationship between niche overlap and species ecological tolerance could nevertheless provide a new tool to apply in future studies.

A Study on Akaike’s Bayesian Information Criterion in Wave Estimation

A feasibility study of Bayesian wave estimation was carried out to investigate the relationship between the minimum Akaike’s Bayesian information criterion (ABIC) and the estimated wave parameters. The ship response functions, which were used for the Bayesian wave estimation together with the ship motion cross spectra, were simply modified and compared with the normal response functions in connection with the accuracy of estimated wave parameters. Moreover, the concept of the ABIC surfaces was introduced to investigate the optimum estimates from the stochastic viewpoint and the physical viewpoint. As the result, it was revealed that the minimum ABIC did not always provide the best estimates from the viewpoint of wave estimation and the simply modified response functions could reduce the estimating errors in some cases. The reasons were considered that the estimating error at the sharp peak of response amplitude operators was closely related to existence of the local minima of the ABIC surface and the simply modified response functions had some effects to make the ABIC surface smoother. It is pointed out as the conclusion of this report that any estimating errors of the ship response functions were not considered in the Bayesian modeling.

Processing of Oversampled Signals in Range on Polarimetric Weather Radars with Mismatched Channels

Processing oversampled signals in range with a whitening transformation has been proposed as a means to reduce the variance of meteorological variable estimates on polarimetric Doppler weather radars. However, the original formulation to construct decorrelation transformations does not account for mismatches in the polarimetric channels, which results in abnormally biased polarimetric variable estimates if the two channels are not perfectly matched. This paper extends the initial formulation and demonstrates that, by properly accounting for the differences in the polarimetric channels, it is always possible to produce optimum estimates of all meteorological variables. Simulation analyses based on the reported characteristics of existing polarimetric radars are included to illustrate the performance of the proposed transformations.