RFLP variability in peanut (Arachis hypogaea L.) cultivars and wild species

Summary RFLP variability was studied in eight U.S. peanut cultivars, representing the four market types, and in 14 wild Arachis species accessions, using random genomic clones from a PstI library. Very low levels of RFLP variability were found among the allotetraploids, which included the U.S. cultivars and Arachis monticola, a wild species. The diploid wild species were very diverse, however. RFLP patterns of the allotetraploids were more complex than the diploids, and the two constituent genomes could usually be distinguished. On the basis of RFLP band sharing, A. ipaensis, A. duranensis, and A. spegazzinii appeared most closely related to the diploid progenitor species of the allotetraploids. A dendrogram of relationships among the diploid wild species was constructed based on band sharing.     

Field uniformity of the Japonica rice region of Taiwan as estimated by relative genetic contribution

Summary Despite the concerns for genetic vulnerability that were raised in the 1970s, the field uniformity of the Japonica rice (Oryza sativa L.) region in Taiwan has increased since 1980 with over 82% of the cultivated areas being covered by as few as three varieties and over half of this hectarage by a single variety. Japanese plant introductions are the major ancestral contributors of genetic constituents for varieties released in Taiwan. The main constitution of the genetic base present in the field has changed little since 1971. Six common ancestors comprised 60%, 55%, 78%, and 77% of the genetic constituents present in the field in 1971, 1976, 1981, and 1986, respectively. These estimates revealed that at least 55% of the genes utilized in the last 15 years came from the same sources. Recent efforts in introducing new germ plasm sources to variety development should continue to alleviate the possible crop loss due to continuous monoculture.Research supported by National Science Council (NSC 78-0211-B005-14)     

Molecular responses of plants to an increased incidence of heat shock

Abstract. Climatic change as a result of the greenhouse effect is widely predicted to increase mean temperatures globally and, in turn, increase the frequency with which plants are exposed to heat shock conditions, particularly in the semi-arid tropics. The consequences of extreme high-temperature treatments on plants have been considered, particularly in relation to the synthesis of heat shock proteins (HSPs) and the capacity to acquire thermotolerance. The heat shock response is described using results obtained with seedlings of the tropical cereals, sorghum ( Sorghum bicolor ) and pearl millet ( Pennisetum glaucum ). A gradual temperature increase, as would occur in the field, is sufficient to induce thermotolerance. The synthesis of HSPs is a transient phenomenon and ceases once the stress is released. Despite the persistence of the HSPs themselves, de novo synthesis of HSPs is required for the induction of thermotolerance each time high temperatures are encountered. The effect of a repeated, diurnal heat shock was investigated and genotypic differences found in the ability to induce the heat shock response repeatedly.     

Species number, species abundance and body length of arboreal arthropods associated with an Australian rainforest tree

Abstract.

• 1 The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over-storey rainforest tree from Australia, Argyrodendron actinophyllum (Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2-year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.
• 2 The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log-series nor the log-normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.
• 3 The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three-dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.
• 4 Although several factors may complicate the interpretation of the three-dimensional plots, long-term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structure in rain forests.

     

Diversity of extinct and living actinistian fishes (Sarcopterygii)

Synopsis A total of 121 actinistian species belonging to 47 genera and 17 undetermined actinistians is reported from the literature. There are 69 valid species with fair assessment of their phylogenetic position; 21 valid species with poor assessment of their phylogenetic position; 31 actinistian incertae sedis; and 18 taxa that had been identified incorrectly as actinistians or are nomen nuda. The fossil record of the actinistians covers a history of approximately 380 million years. The greatest diversity occurred during the Scythian (Early Triassic).     

Clonal diversity, population structure, and dispersal in the parthenogenetic moth Ectoedemia argyropeza

Populations of the parthenogenetic moth Ectoedemia argyropeza (Lepidoptera, Nepticulidae) were studied for their clonal composition. Clones were characterized by 6 polymorphic enzyme loci. In a geographic survey 32 clones were observed among 812 individuals. Two clones were predominant, together they explained over 75% of the total variation. Relationships among clones hinted at a monophyletic origin of the species. Analysis of the life cycle and population structure indicated that E. argyropeza is a very sedentary species, with bottlenecks, drift, and passive migration as important population genetical factors moulding the variation.     

Factors influencing species diversity in saline waters of Death Valley,USA

Salinity is a major factor influencing the distributions and abundances of aquatic macroinvertebrates of saline waters in Death Valley, California, USA. A general pattern of declining numbers of species with increasing salinity is seen in Death Valley waters. Some species are restricted to low salinities, others are found only in highly saline pools, and still others are widely distributed over a broad range of salinities.Salinity alone cannot explain distributions seen in the field. Distributions and abundances of species such as the caddisfly Limnephilus assimilis Banks are broader than would be predicted on the basis of laboratory studies of salinity and temperature. I present evidence that for such species, biotic factors such as reduced predation at high salinities may compensate for increased physiological stress.     

Spatial distribution of species diversity indices and their correlation with plot size

In a physiognomically uniform Leucobryo-Pineteum phytocoenose the spatial pattern of point diversity was determined and the effect of quadrat size on the assessment of alpha diversity (in Whittaker's, 1977, sense) was analysed. In both cases the Shannon index of total species diversity and the evenness index were used to measure diversity. A contagious spatial pattern of point diversity and a high variation of point diversity values, as well as a strong non-linear dependence of H and J values on quadrat size, and also a decrease in H and J variation with an increase in quadrat size were found.Nomenclature follows Ehrendorfer (1973). Liste der Gefässpflanzen Mitteleuropas.     

Biomass: Is it a useful tool in paleocommunity reconstruction?

In general, more of the biomass of the community is preserved than is its numerical abundance. Thus, the paleontologist, on the average, works with more of the community when biomass is used. Community characteristics such as taxon dominance and habitat proportions are at least as accurately derived from biomass as numerical abundance. The use of biomass is clearly more appropriate in describing energy flow and trophic proportions. Whenever possible, biomass should be used as a complement to numerical abundance in future paleoecologic reconstructions.