Phylogeography and genetic structure of the Mediterranean killifish <Emphasis Type="Italic">Aphanius fasciatus</Emphasis> (Cyprinodontidae)

The purpose of this study was to determine the phylogeographic structure of the brackish-hypersaline cyprinodont fish Aphanius fasciatus (Valenciennes, 1821), using sequencing and RFLP analysis of a 1,330 bp mitochondrial DNA segment containing part of the 16S rRNA gene as well as the genes for tRNA-Leu, NADH subunit 1 and tRNA-Ile. Individuals were collected from 13 different sites in Greece and Turkey, while seven published A. fasciatus sequences were also included to cover the area of distribution of the species. Pairwise sequence divergence values ranged from 0 to 4.51%. Congruent phylogenies were recovered with maximum likelihood, maximum parsimony and neighbour-joining methods. All analyses revealed two main groups. The first group consists of populations from almost all localities that drain into the Aegean Sea. The second group comprises the remaining population samples, which in some cases seem to consist of population-specific subgroups. Our results show that vicariant events have predominantly affected the evolution of A. fasciatus, with the Messinian salinity crisis having shaped the present genetic structure of its populations. Additionally, the life-history traits of the species, which determine a low potential for dispersal, coupled with the typical fragmentation of brackish-hypersaline water habitats have led to a high degree of isolation of A. fasciatus populations, even at restricted spatial scales. Analysis of the partitioning of the total amount of polymorphism with analyses of molecular variance (AMOVA) gave a value of F _ST = 84.6%. Potential conservation policies concerning A. fasciatus should also consider the low-genetic variability in the majority of its populations and the presence of fixed haplotypes in some of them.     

Interannual, seasonal, local and body size variations in reproduction of the prawn Penaeus (Marsupenaeus) japonicus (Crustacea: Decapoda: Penaeidae) in the Ariake Sea and Tachibana Bay, Japan

 The reproductive biology of female Penaeus japonicus Bate was investigated in the Ariake Sea and Tachibana Bay (located outside the Ariake Sea), Japan from 1994 to 1996. Interannual, seasonal, individual female body size and spatial influences on the incidence of spawning were examined. The proportion of inseminated females, increased with increasing body size up to 170 mm body length (BL) and decreased thereafter. The minimum size at maturity was similar between years; 130 to 140 mm BL. The minimum size of individuals with developing ovaries or spermatophores differed from that of ripe females by 20 to 25 mm. Spawning occurred in the central part of the Ariake Sea and Tachibana Bay but rarely in the inner part. P. japonicus had a clear reproductive cycle. Spawning started earlier and ended later, occurring from mid-May to mid-October, in the eastern central part of and outside of the Ariake Sea compared with the western central part, where spawning occurred from mid-June to mid-September. Spawning dynamics differed across seasons, body sizes and areas but not across years. The seasonal peak in the proportion of ripe females varied with body size. In small individuals (130 to 169 mm BL), no peak was observed, whereas in large individuals (>170 mm BL) the proportion of ripe individuals peaked in June. The proportion of ripe individuals increased with increasing body size and was high outside the Ariake Sea. Factors causing the variation in spawning dynamics are discussed. Received: 30 November 1998 / Accepted: 12 October 1999     

Geographic shifts in the highland cooking banana (Musa spp., group AAA-EA) production in Uganda

Summary

Between 1970 and 1990 Uganda witnessed the decline of the highland cooking banana from traditional growing areas in the central region, coupled with crop expansion in the country's southwest. Apprehension that the factors leading to loss of sustainability in the central region may be replayed in extant production areas has raised concern about the future of the cooking banana in Uganda. Consequently, a multi-disciplinary study was conducted at nine central and six southwestern sites to document shifts in cooking banana production and to elucidate the causes behind these shifts.

Cooking banana production in central Uganda sites fell from 18% of total food crop and 7% of total cash crop production in the 1970s to 4% and 2%, respectively, in the 1990s. Farmers identified reduced labour availability and management, increasing pest pressure and declining soil nutrient status as the major causes of decline. On-farm verification confirmed farmers' observations: weevil levels were the highest yet found in Uganda, while foliar samples indicated deficiencies in magnesium, nitrogen, and potassium. Soil nutrient deficiencies, however, appear to be a direct outcome ofreduced management rather than ‘soil exhaustion’ as postulated by farmers.

In southwestern Uganda, the importance of the cooking banana as a cash crop has quadrupled since 1970. Banana first penetrated the region because of its ease of production and stability of yield. High yields attracted traders and urban market demand drove further crop expansion. With current market incentives, banana management standards have been high. Under current levels of management, it is unlikely that farmers in southwestern Uganda will experience a similar process of decline as that which occurred in the central region. However, concern remains aboqt lack of replenishment of nutrients leaving the farm in the form of fruits sold for market, a nutrient loss which may eventually lead to non-sustainability of the cropping system.     

Sexual reproduction of the photosymbiotic ascidian <Emphasis Type="Italic">Diplosoma virens</Emphasis> in the Ryukyu Archipelago,Japan: vertical transmission,seasonal change,and possible impact of parasitic copepods

Diplosoma virens is a colonial ascidian hosting prokaryotic algae Prochloron sp. in the common cloacal cavity of the colonies and is sometimes parasitized by notodelphyid copepods. In ascidian–Prochloron symbiosis, it is generally known that the host larvae acquire the algal symbionts from their mother colonies to maintain the symbiosis. A histological study of the sexually mature colonies of D. virens showed that the algal symbionts attach to pre-hatching larvae on the rastrum (plant rake) projected from the postero-dorsal part of the larval trunk, and then the rastrum is packed in the posterior half of the larval trunk that will become a cloacal cavity after metamorphosis. This process is the same as that of D. simile. Monthly sampling of D. virens colonies showed that they have embryos in summer in Ryukyus, situated near the northern-most limit of the coral reefs in the West Pacific. While the frequencies of copepod parasitism were variable among the populations, the colonies from a highly parasitized population had a significantly smaller number of eggs/embryos per zooid than the colonies from the less parasitized populations. The parasites probably have an inhibitory impact on the sexual reproduction of the host colonies.Communicated by T. Ikeda, Hakodate     

Ultrastructural alterations on chloride cells of the yellowtail Seriola quinqueradiata,following exposure to the red tide species Chattonella antiqua

By means of scanning and transmission electron microscopy, the influence of the red tide species Chattonella antiqua was examined with respect to the surface ultrastructures of chloride cells of the yellowtail Seriola quinqueradiata. Conspicuous ultrastructural alterations occurred on the apical surface of these cells. The majority of chloride cells in the control gills showed an apical surface with numerous cellular extensions, while more than half the chloride cells affected by red tide organisms exhibited an apical surface with fewer and smaller extensions, a wrinkled apical surface, or a protruded apical surface. These ultrastructural alterations of chloride cell surface may be due to the partial disturbance of salinity by C. antiqua, and reflect the changes of the ion-transport function in yellowtail gills exposed to red tide water.     

A statistical evaluation of non-ergodic variogram estimators

Geostatistics is a set of statistical techniques that is increasingly used to characterize spatial dependence in spatially referenced ecological data. A common feature of geostatistics is predicting values at unsampled locations from nearby samples using the kriging algorithm. Modeling spatial dependence in sampled data is necessary before kriging and is usually accomplished with the variogram and its traditional estimator. Other types of estimators, known as non-ergodic estimators, have been used in ecological applications. Non-ergodic estimators were originally suggested as a method of choice when sampled data are preferentially located and exhibit a skewed frequency distribution. Preferentially located samples can occur, for example, when areas with high values are sampled more intensely than other areas. In earlier studies the visual appearance of variograms from traditional and non-ergodic estimators were compared. Here we evaluate the estimators' relative performance in prediction. We also show algebraically that a non-ergodic version of the variogram is equivalent to the traditional variogram estimator. Simulations, designed to investigate the effects of data skewness and preferential sampling on variogram estimation and kriging, showed the traditional variogram estimator outperforms the non-ergodic estimators under these conditions. We also analyzed data on carabid beetle abundance, which exhibited large-scale spatial variability (trend) and a skewed frequency distribution. Detrending data followed by robust estimation of the residual variogram is demonstrated to be a successful alternative to the non-ergodic approach.     

Associations of forest bird species richness with housing and landscape patterns across the USA.

In the United States, housing density has substantially increased in and adjacent to forests. Our goal in this study was to identify how housing density and human populations are associated with avian diversity. We compared these associations to those between landscape pattern and avian diversity, and we examined how these associations vary across the conterminous forested United States. Using data from the North American Breeding Bird Survey, the U.S. Census, and the National Land Cover Database, we focused on forest and woodland bird communities and conducted our analysis at multiple levels of model specificity, first using a coarse-thematic resolution (basic models), then using a larger number of fine-thematic resolution variables (refined models). We found that housing development was associated with forest bird species richness in all forested ecoregions of the conterminous United States. However, there were important differences among ecoregions. In the basic models, housing density accounted for < 5% of variance in avian species richness. In refined models, 85% of models included housing density and/or residential land cover as significant variables. The strongest guild response was demonstrated in the Adirondack-New England ecoregion, where 29% of variation in richness of the permanent resident guild was associated with housing density. Model improvements due to regional stratification were most pronounced for cavity nesters and short-distance migrants, suggesting that these guilds may be especially sensitive to regional processes. The varying patterns of association between avian richness and attributes associated with landscape structure suggested that landscape context was an important mediating factor affecting how biodiversity responds to landscape changes. Our analysis suggested that simple, broadly applicable, land use recommendations cannot be derived from our results. Rather, anticipating future avian response to land use intensification (or reversion to native vegetation) has to be conditioned on the current landscape context and the species group of interest. Our results show that housing density and residential land cover were significant predictors of forest bird species richness, and their prediction strengths are likely to increase as development continues.     

Effect of white African mineral hair dye on the activities of phosphatases and malondialdehyde level in selected tissues of albino rats

The effect of white African mineral dye Yombofita (YF) on the activities of alkaline phosphatase (ALP), acid phosphatase (ACP) and malondialdehyde (MDA) levels in the skin, liver, kidney and serum of albino rats was investigated. The chemical analysis of the dye was first carried out using solubility test, pH determination and X-ray fluorescence (XRF) elemental analysis. Six different concentrations (0.05, 0.15, 0.25, 0.5, 0.75 and 1.00%) of the dye were prepared using hydrogen peroxide (30 volume) as solvent. A total of 80 albino rats (Rattus norvegicus) were used for the study. The rats were divided into 8 groups of 10 each and were maintained on commercial feed for the period of the experiment i.e. 30 days. In group 1, the control group, the animals were applied distilled water on their heads, whereas in group 2 the vehicle i.e. hydrogen peroxide was applied. In groups 3 to 8 various concentrations of YF (white) dye ranging from 0.05, 0.15, 0.25, 0.5, 0.75 to 1.00% was applied respectively. At the end of the experiment, blood samples were collected and portions of the selected tissues were excised for the determination of ALP and ACP activities. The MDA level was also determined in the skin of experimental animals. The results revealed a significant decrease (p?p?相似文献