Factors Associated with Grassland Bird Species Richness: The Relative Roles of Grassland Area, Landscape Structure, and Prey

The factors responsible for widespread declines of grassland birds in the United States are not well understood. This study, conducted in the short-grass prairie of eastern Wyoming, was designed to investigate the relationship between variation in habitat amount, landscape heterogeneity, prey resources, and spatial variation in grassland bird species richness. We estimated bird richness over a 5-year period (1994–1998) from 29 Breeding Bird Survey locations. Estimated bird richness was modeled as a function of landscape structure surrounding survey routes using satellite-based imagery (1996) and grasshopper density and richness, a potentially important prey of grassland birds. Model specification progressed from simple to complex explanations for spatial variation in bird richness. An information-theoretic approach was used to rank and select candidate models. Our best model included measurements of habitat amount, habitat arrangement, landscape matrix, and prey diversity. Grassland bird richness was positively associated with grassland habitat; was negatively associated with habitat dispersion; positively associated with edge habitats; negatively associated with landscape matrix attributes that may restrict movement of grassland bird; and positively related to grasshopper richness. Collectively, 62% of the spatial variation in grassland bird richness was accounted for by the model (adj-R² = 0.514). These results suggest that the distribution of grassland bird species is influenced by a complex mixture of factors that include habitat area affects, landscape pattern and composition, and the availability of prey.     

Postcards from the past: charting the landscape-scale conversion of tropical Australian savanna to closed forest during the 20th century

Repeated sequences of digitised and geo-referenced historical aerial photography provide a powerful means of understanding landscape change. We use this method to demonstrate a landscape wide expansion of closed forest (42% increase in total coverage) in the Australian monsoon tropics over the past five decades. Retrospective habitat suitability models (HSI) of closed forest derived using four landscape measures (drainage distance, slope angle, aspect and elevation) for imagery taken in 1947 correctly forecast the subsequent spatial distribution of the expansion, with topographic fire protection primarily determining the closed-forest distribution. The dynamics of the closed forest-savanna boundary were predicted accurately by generalised linear models, with closed-forest expansion in fire-protected sites along forest edges and regression in the more fire-prone areas. Two factors may plausibly explain the expansion of closed forests. First, eco-ethnographic records stress the skilful use of fire by Aboriginal people in protecting isolated and locally resource-rich closed-forest patches. Second, the recent global increase in atmospheric CO₂ may be changing the competitive balance between savanna and forest by enabling C₃ trees to grow fast enough to escape the fire trap presented by flammable C₄ grasses.     

Concentrations of constitutive alk(en)ylresorcinols in peel of commercial mango varieties and resistance to postharvest anthracnose

Mature green mango fruits of commercially important varieties were screened to investigate the levels of constitutive antifungal compounds in peel and to assess anthracnose disease after inoculation with Colletotrichum gloeosporioides. High-pressure liquid chromatography was used to quantify the levels of 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol in the peel extracts. The fruit peel of the varieties ‘Kensington Pride’ and ‘Keitt’ were observed to have the highest levels of both 5-n-heptadecenylresorcinol (107.3–123.7 and 49.9–61.4 μg/g FW, respectively) and 5-n-pentadecylresorcinol (6.32–7.99 and 3.30–6.05 μg/g FW, respectively), and the fruits of the two varieties were found to have some resistance to postharvest anthracnose. The varieties ‘Kent’, ‘R2E2’, ‘Nam Doc Mai’, ‘Calypso’ and ‘Honey Gold’ contained much lower concentrations of resorcinols in their peel and three of these varieties were found to be more susceptible to anthracnose. Concentrations of 5-n-heptadecenylresorcinol were significantly lower at the ‘sprung’ and ‘eating ripe’ stages of ripening compared to levels at harvest. Concentrations of 5-n-pentadecylresorcinol did not differ significantly across the three stages of ripening. The levels of these two resorcinols were found to be strongly inter-correlated (P<0.01, r²=0.71), with concentrations of 5-n-heptadecenylresorcinol being an average 18 times higher than those of 5-n-pentadecylresorcinol. At the ‘eating ripe’ stage, significant relationships were observed between the concentrations of each type of alk(en)ylresorcinol and anthracnose lesion areas following postharvest inoculation, P<0.001, r²= 0.69 for 5-n-pentadecylresorcinol, and P<0.001, r²= 0.44 for 5-n-heptadecenylresorcinol.     

Seasonal development of secondary xylem in Pinus Strobus L.

Secondary xylem, or wood, is the tissue that conducts water and minerals in the tree; thus it performs physiologically one of the most important functions for the tree. In addition secondary xylem is the tissue that primarily determines the suitability of a tree for various economic uses.Investigation of the development of secondary xylem shows that it was gradual. Xylem mother cells, the immediate derivatives of cambial initals, were, at first, small cells with thin cell walls. Then the xylem mother cells enlarged radially, but still retained thin cell walls. When these cells reached the radial diameter of mature tracheids, the secondary wall deposition began. This continued until thick, rigid cell walls were attained. These thick, rigid walls determine the physical properties of a certain species of wood. This investigation shows that physical properties of tracheids can differ with stages of development.

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Zusammenfassung Das Sekundärxylem, oder das Holz, ist dasjenige Gewebe, welches Wasser und Mineralstoffe im Baum führt. Damit erfüllt es eine der wichtigsten physiologischen Funktionen für den Baum. Außerdem bestimmt das Gewebe des Sekundärxylems in erster Linie die Verwendbarkeit des Baumes bzw. des Holzes zu wirtschaftlichen Zwecken. Die Untersuchung der Entwicklung des Sekundärxylems zeigte, daß diese Entwicklung abgestuft vor sich geht. Die Xylem-Mutterzellen, unmittelbare Abkömmlinge der Kambium Initialen, zeigten sich zuerst als kleine Zellen mit dünnen Zellwänden. Dann erweiterten sie sich in radialer Richtung, blieben aber immer noch dünn in ihren Zellwänden. Als diese Zellen etwa den Durchmesser von reifen Tracheiden erreicht hatten, begann die Auflagerung der Sekundärschicht. Dieser Vorgang setzte sich fort bis sich dicke, feste Zellwände gebildet hatten. Diese dicken, steifen Zellwände bestimmen weitgehend die physikalisch-mechanischen Eigenschaften der betreffenden Holzart. Die vorliegenden Untersuchungen zeigen, daß die physikalischen Eigenschaften der Tracheiden je nach der Entwicklungsstufe schwanken können.

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This report is based on portions of work in fulfillment of the requirements for the Ph.D. degree in Botany at the University of Wisconsin.

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Maintained at Madison, Wisconsin, 53705, U. S. A., in cooperation with the University of Wisconsin.     

Cell wall formation in secondary xylem of Pinus strobus L.

Summary Vesicular membrane-bound bodies that participate in forming the cell wall of differentiating xylem cells in white pine appeared on electron microscopical examination to originate from the Golgi apparatus. Golgi bodies released vesicles that contained dark material, fibrillar material, or no contents. The vesicles were seen at different stages on their path to the cell wall; their contents came in contact with the wall by fusion of vesicular membranes with the plasmalemma. Individual filaments of fibrillar material within the vesicles were 60 to 80 Å in diameter; structurally they resembled the fibrillar component of the existing wall and became intertwined with the wall. The authors assume the dark material in the Golgi-derived vesicles represents the hemicellulosic and the pectic components of the wall, and the fibrillar material, the cellulosic.Maintained in cooperation with the University of Wisconsin.     

Variation of heartrot,sapwood infection and polyphenol extractives with provenance of Acacia mangium

Infection of heartwood by decay fungi (heartrot) is a concern for growers of Acacia mangium for solid‐wood products as the incidence can be high in some regions of Indonesia. Variation of heartrot incidence for different provenances of A. mangium was determined using two field trials in Sumatra, Indonesia. In a Riau Province trial of 21 provenances, the effect of provenance was statistically significant for natural heartrot incidence, which ranged from 1.6% to 27.2%. In a smaller trial using artificial inoculation in South Sumatra, heartwood infection incidence ranged from 39.4% to 70.8% across six provenances and both wound type and provenance were statistically significant factors. There was also significant variation in sapwood infection length related to provenance. Wood extractives (yield, total phenols, protein‐precipitable tannin and 2,3‐trans‐3,4′,7,8‐tetrahydroxyflavanone) were quantified from a subsample of trees for each trial. However, no significant differences in extractive concentration were detectable according to provenance and evidence for a relationship between heartwood extractives and heartrot incidence was generally poor. While further studies need to be completed to establish the basis for heartrot incidence, results from these trials allow for recommendations on provenance selection to reduce heartrot incidence and provide information for further genetic selection programmes.     

A highly specific enzyme-linked immunosorbent assay for the detection of Cry1Ac insecticidal crystal protein in transgenic WideStrike cotton

A highly selective enzyme-linked immunosorbent assay (ELISA) has been developed for the quantitative detection of the Cry1Ac protein expressed in transgenic cotton. Two Cry1Ac-specific monoclonal antibodies (MAb), Kbt and 158E6, were developed and selected to form a sandwich format ELISA. The MAb Kbt was used as a capture antibody, and 158E6 was conjugated with horseradish peroxidase and served as a detection antibody. The assay was optimized and validated with different cotton matrices. Tissues were extracted with phosphate-buffered saline containing 0.05% Tween 20 and 1% polyvinylpyrrolidone. The extract was then treated with trypsin to truncate full-length Cry1Ac into the core toxin for quantitation. The resulting assay has good accuracy and precision with a validated limit of quantitation ranging from 0.1 to 0.375 mug/g dry weight of cotton tissues. This assay is highly specific for Cry1Ac protein and has no cross-reactivity with the nontarget proteins tested such as Cry1Ab and Cry1F.     

Phylogeny of Fusarium oxysporum f. sp. lactucae Inferred from Mitochondrial Small Subunit, Elongation Factor 1-alpha, and Nuclear Ribosomal Intergenic Spacer Sequence Data

ABSTRACT Fusarium oxysporum f. sp. lactucae, causal agent of Fusarium wilt of lettuce, is a serious pathogen recently reported in Arizona. Sequence analysis of the mitochondrial small subunit (mtSSU), translation elongation factor 1-alpha (EF-1alpha) gene, and the nuclear ribosomal DNA intergenic spacer (IGS) region was conducted to resolve relationships among f. sp. lactucae isolates, F. oxysporum isolates from other hosts, and local non-pathogenic isolates. Analysis of mtSSU sequences provided limited phylogenetic resolution and did not differentiate the lactucae isolates from 13 other F. oxysporum isolates. Analysis of EF-1alpha sequences resulted in moderate resolution, grouping seven formae speciales with the lactucae isolates. Analysis of the IGS region revealed numerous sequence polymorphisms among F. oxysporum formae speciales consisting of insertions, deletions, and single nucleotide transitions and substitutions. Repeat sequence analysis revealed several duplicated subrepeat units that were distributed across much of the region. Based on analysis of the IGS sequence data, lactucae race 1 isolates resolved as a monophyletic group with three other formae speciales of F. oxysporum. In all analyses, lactucae race 2 isolates composed a separate lineage that was phylo-genetically distinct and distantly related to the lactucae race 1 isolates.     

Anti-Müllerian Hormone as a Diagnostic Marker for Equine Cryptorchidism in Three Cases with Equivocal Testosterone Concentrations

Cryptorchidism is a developmental disorder which can be diagnosed by a variety of different tests. Still, equine field veterinarians often rely on endocrine markers to detect retained testicular tissue. This report describes the value of anti-Müllerian hormone (AMH) as a diagnostic marker for cryptorchidism in three stallions suspected of cryptorchidism, with equivalent serum testosterone concentrations. A single measurement of AMH identified cryptorchidism, with inconclusive testosterone concentrations as either gelding or stallion. Furthermore, a human chorionic gonadotropin (hCG) stimulation test or surgery was performed to support the diagnostic value of AMH. To conclude, the endocrine panel for cryptorchidism should be expanded to include determination of serum AMH, as this determination can increase the diagnostic accuracy of a single blood sample.