Racemization of the aqua-{N-salicylidene-(S)-alaninato}copper(II) by reaction with potassium cyanate

Copper(II) N-salicylidene-(S)-alaninate trihydrate reacting as the S-enantiomeric parent compound with KOCN in hot diluted methanol yielded by slow crystallisation from the cooled reaction mixture (in the course of 1 day) the racemic product K[Cu{sal-(RS)-ala}(NCO)]. The parameters of the axial type EPR spectrum in X-band region and the LF band position in the electronic spectrum are typical of an axially distorted square pyramidal coordination of the Cu(II) atom in this complex. The spectral properties of the complex cuprate prepared and its basal crystallographic data are consistent with those of the earlier studied¹⁵ K₂[Cu₂{sal-(RS)-ala}₂(μ-NCO)₂] synthetized by using [Cu{sal-(RS)-ala}(H₂O)].H₂O as the racemic parent complex in the reaction mixture with KOCN.     

Dynamics of distribution in animal communities: Theory and analysis

Theoretical and analytical problems of the dynamics of distribution and abundance in animal communities were examined. In many communities, species with low abundance and of limited spatial occurrence (i.e., rare species) typically form a conspicuous peak when a frequency distribution of the number of species is constructed with respect to the proportion of sites occupied within an area of distribution. Models of distribution dynamics, including a new model proposed here, were compared with a range of animal community data using a new procedure to assess single- and bi-modal patterns in frequency distributions of spatial occurrence. Data reveal that single-modality with an excess of rare species occurs more frequently than bimodality. Even when bimodality is detected, the mode representing wide-spread species is in the majority of cases smaller than that for rare species. Thus, a new model in which the rate of local extinctions is assumed to be negatively related to patch occupancy (or population abundance) is in better agreement with observed data than earlier models. Some problems of analysis, in particular model assumptions and testing, are discussed.     

Kin-structured migration and the rate of advance of an advantageous gene

Hemoglobin E, an allele generally considered to confer malarial resistance in heterozygotes, is found in high frequencies across a wide area of Southeast Asia. Apparently it originated as a single-point mutation which was spread by gene flow. The rate of diffusion of this adaptive allele is studied using four computer simulation models. It is shown that in small populations deterministic equations for gene flow may overestimate rates of diffusion. Other aspects of population structure, however, such as kin-structuring of migrant groups, increase the rate of advance. Finally, population growth coupled with the spread of the allele leads to much more rapid diffusion. These results suggest that population structure can be an important factor affecting the diffusion of advantageous genes.     

Book reviews

Editing of community data matrices is complementary to analyzing data by multivariate techniques of classification and ordination in the overall task of data analysis. A computer program, DATAEDIT, is described that can perform numerous editing functions, including data transformation, deletion of certain species or samples, deletion of rare species, deletion of outliers, separation of disjunet sample groups, reordering of the species or samples of a data matrix, and the formation of composite samples or of sample subsets. DATAEDIT can use the information in a nonhierarchical or hierarchical classification, and includes its own internal routine for reciprocal averaging ordination.We appreciate valuable suggestions from the late Robert H. Whittaker, and from Philip Dixon, David Hieks, Laura Huenneke, Linda Olsvig-whittaker, and Mark Wilson. Mark O. Hill kindly supplied a fast subroutine for reciprocal averaging.