Fine‐scale Population Genetic Structure of Two Dioecious Indian Keystone Species,Ficus hispida and Ficus exasperata (Moraceae)

Although Ficus (Moraceae) is a keystone plant genus in the tropics, providing resources to many frugivorous vertebrates, its population genetic structure, which is an important determinant of its long‐term survival, has rarely been investigated. We examined the population genetic structure of two dioecious fig species (Ficus hispida and Ficus exasperata) in the Indian Western Ghats using co‐dominant nuclear microsatellite markers. We found high levels of microsatellite genetic diversity in both species. The regression slopes between genetic relationship coefficients (f_ij) and spatial distances were significantly negative in both species indicating that, on average, individuals in close spatial proximity were more likely to be related than individuals further apart. Mean parent–offspring distance (σ) calculated using these slopes was about 200 m in both species. This should be contrasted with the very long pollen dispersal distances documented for monoecious Ficus species. Nevertheless, overall population genetic diversity remained large suggesting immigrant gene flow. Further studies will be required to analyze broader scale patterns.     

Links between global taxonomic diversity,ecological diversity and the expansion of vertebrates on land

Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.     

Indigenous domestic breeds as reservoirs of genetic diversity: the Argentinean Creole cattle

Contrary to highly selected commercial breeds, indigenous domestic breeds are composed of semi-wild or feral populations subjected to reduced levels of artificial selection. As a consequence, many of these breeds have become locally adapted to a wide range of environments, showing high levels of phenotypic variability and increased fitness under natural conditions. Genetic analyses of three loci associated with milk production (alpha(S1)-casein, kappa-casein and prolactin) and the locus BoLA-DRB3 of the major histocompatibility complex indicated that the Argentinean Creole cattle (ACC), an indigenous breed from South America, maintains high levels of genetic diversity and population structure. In contrast to the commercial Holstein breed, the ACC showed considerable variation in heterozygosity (H(e)) and allelic diversity (A) across populations. As expected, bi-allelic markers showed extensive variation in He whereas the highly polymorphic BoLA-DRB3 showed substantial variation in A, with individual populations having 39-74% of the total number of alleles characterized for the breed. An analysis of molecular variance (AMOVA) of nine populations throughout the distribution range of the ACC revealed that 91.9-94.7% of the total observed variance was explained by differences within populations whereas 5.3-8.1% was the result of differences among populations. In addition, the ACC breed consistently showed higher levels of genetic differentiation among populations than Holstein. Results from this study emphasize the importance of population genetic structure within domestic breeds as an essential component of genetic diversity and suggest that indigenous breeds may be considered important reservoirs of genetic diversity for commercial domestic species.     

Seasonal and interannual variation in the energetic condition of adult male Atlantic sharpnose shark Rhizoprionodon terraenovae in the northern Gulf of Mexico

One hundred and thirty Atlantic sharpnose shark Rhizoprionodon terraenovae livers were collected from April 1999 to October 2001 from inshore waters of the Mississippi Sound to investigate seasonal and inter‐annual variation in their energetic condition. A decline in the hepato‐somatic index ( I _H) was observed from 1999 to 2001. In addition, I _H, liver specific energy content and total energy content were lowest during the summer and highest during the spring and autumn, while liver water content was highest during the summer and lowest during the spring and autumn.     

Instrumental test to estimate a model of forecast yield: a non-parametric application to the pollen index in South Italy

A statistical test is described to verify the characteristics of the biological information contained in the dynamics of the flowering process. The test focuses on interactions between the pollen index and climatic variables to investigate if the biological indicator can synthesise the information of the pre-flowering phases. The multiple-regression model is built upon two pre-flowering climate macro-indicators extracted by Principal Component Analysis (PCA) and the optimised pollen index is obtained by non-parametric estimation. The empirical analysis is applied to 15 stations located in southern Italy in regions that have a longstanding tradition of olive production. Using the variance explained, we find that an optimised pollen index is fairly well predicted by the pre-flowering climatic data. We conclude that the optimised pollen index makes more parsimonious the modelling for predicting olive production.     

The fate of15N labeled nitrogen applied to mature citrus trees

Summary The efficiency and balance of nitrogen from one year's application was studied in a long-term fertigation experiment. Enriched nitrogen fertilizer, K¹⁵NO₃, was applied to a 22-year-old Shamouti orange tree with a history of high N applications (N₃) and to an N-starved tree (N₁). The distribution of N in the different parts of the trees and in the soil was determined after the experimental trees were excavated. Similar total recovery of the labeled fertilizer N was found in the trees and soil in both treatments (N₁−61.7% N₃−56%). However, the distribution between tree and soil was different. The amount of recovered residual fertilizer in the soil was much larger in the N₃ treatment than in N₁. The highest percentage of fertilizer N was found in the new organs,i.e. fruits, twigs and leaves. The roots and branches took up only 6–14% from the labeled fertilizer. Only 20.9% of the leaf N and 23.4% of the fruit N in the N₃ tree originated in the labeled fertilizer, indicating translocation of N from older parts of the tree to new growth. Evidence was found of storage of N in the wooded branches, while the roots contained a surprisingly small part of labeled fertilizer. Contribution 1599E.     

Cultivar and Rhizobium strain effect on nitrogen fixation and transport inPhaseolus vulgaris L.

The effects of Rhizobium strain and its interaction with plant cultivar were examined in glasshouse-grownPhaseolus vulgaris in two experiments where the physiological attributes defining the symbiotic efficiency were determined. Strains of Rhizobium significantly affected nodulation, rates of N accumulation, partitioning of N within the mature shoot and remobilizaton of the N stored in the vegetative organs to the seeds. The most efficient symbiosis (strain CO5 with Negro Argel), in comparison with the least efficient symbiosis (strain 127 K-17 with Venezuela-350) showed higher rates of C₂H₂ reduction from flowering to mid pod fill stage, evolved less hydrogen from nodules and showed higher rates of N transport as well as higher percentages of ureide-N in the xylem sap. At maturity, the best cultivar/strain association exceeded the total N accumulated in the seed and the harvest index of the poorest symbiosis in 88% and 20%, respectively. The other symbiotic combinations were intermediate in all characteristics. Nitrogen accumulation in plant shoot showed highly significant correlation with acetylene reduction rates, nodule relative efficiency, total N transport in the xylem sap and percentage of N transported as ureides.     

Relation between electrokinetic potentials and growth in callus cultures ofTrigonella foenum-graecum

Callus cultures ofTrigonella foenum-graecum were initiated from radicle or cotyledon portions of seedlings and young leaves and maintained on modified 1-B5 medium. The callus mass was disaggregated by mechanical agitation and the discrete cells thus obtained were used to measure their electrokinetic potential. Studies pertaining to the effects of ageing on electrokinetic potential and growth index revealed a relationship between these two parameters. Thus, the rate of change of electrokinotie potential with age could be employed as a parameter to study the growth kinetics of cells in callus cultures.