How far bowalization affects phytodiversity,life forms and plant morphology in Sub‐humid tropic in West Africa

Bowal or ferricrete, the final of land degradation, occurred only in tropical region. This study aimed at assessing the effects of bowalization on phytodiversity, life forms and morphological response of plant species using Combretum nigricans Leprieur ex Guill. & Perr. as a case study. Morphological parameters (height, number of stems, number of branches, diameter at breast height and crown diameter) of C. nigricans were determined in the sub‐humid zone of Benin. Plant communities were determined according to Multi‐Response Permutation Procedures analysis. Plant communities were more diversified on sand‐clay and concretion soils (control) compared with those described on bowal. C. nigricans developed more stems (3.6 ± 1.4 stems vs. 1.3 ± 0.4 stems), more branches (5.9 ± 2.4 branches vs. 3.2 ± 0.6 branches) and large crown diameter (5 ± 1.48 m vs. 3.4 ± 1.2 m) on bowal than on sand‐clay soil. The best adapted life forms on bowal were therophytes. Bowalization induced loss of phytodiversity, changes in species life forms and provoked local adaptation of tree species.     

Trans-ethnic variation in germline variants of patients with renal cell carcinoma

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Geographical isolation and genetic differentiation: the case of Orestias ascotanensis (Teleostei: Cyprinodontidae), an Andean killifish inhabiting a highland salt pan

Orestias ascotanensis is a killifish endemic to the Ascotán salt pan in the Chilean Altiplano, where it inhabits 12 springs with different degrees of isolation. This species is a suitable model for studying the effect of serial geographical isolations on the differentiation process among populations. The present study examines the genetic variation and structure of the species using mitochondrial DNA control region sequences and eight microsatellite loci, analyzing populations across its distribution range. The evaluation of genetic variation revealed high levels of diversity within the species. The genetic structure analysis showed the existence of four differentiated groups: two groups were formed by the springs located in the northern and southern extremes of the salt pan and two groups were found in the centre of the salt pan. The latter two groups were formed by several springs, most likely as a consequence of the South American summer monsoon that could connect them and allow gene flow. The patterns of genetic differentiation appear to be determined based on the physical isolation of the populations. This isolation may be the result of a combination of factors, including geographical distance, a historical decrease in water levels and altitude differences in the springs of the salt pan. Therefore, this system is a rare example in which hydrological factors can explain genetic differentiation on a very small scale.     

Reply to Hatch and Prihoda

The authors thank Jeff Prince, Ph.D. for his editorial assistance.     

Sequence Analysis of the Internal Transcribed Spacer 2 (ITS2) from Yeast Species Within the Genus Candida

Nucleotide sequences of the internal transcribed spacer 2 (ITS2) regions were determined for 13 species within the genus Candida, representing a collection of those species pathogenic for humans. No two species had identical sequences and the sizes of ITS2 varied fourfold, representing an apparent continuous gradient of nucleotides. When present, sequence homologies were observed in the 5′ end of ITS2, and many species exhibited more limited homologies within three known conserved domains found in other yeasts. Cluster analysis of primary sequence revealed a concordance with a known taxonomic subfamily and suggests that certain species within the genus form a similar grouping. A majority of species exhibited similar presumptive RNA secondary structures, consistent with the hypothesis that these spacer regions are essential for correct processing of the 5.8S and 28S subunits. Received: 14 April 1997 / Accepted: 22 July 1997