Phylogenetic relationships in the genus Closterium

Desmids are a large polyphyletic group of streptophyte algae, numbering about 4000 species. Traditionally, the taxonomy of desmids is based on morphological characters. However, the latest molecular genetic studies of the group conflict with the established taxonomy and indicate the polyphyletic position of some genera of this group of algae. The genus Closterium Nitzsch ex Ralfs, like the family Closteriaceae Bessey, forms a monophyletic clade on the general tree of Desmidiales, recovered on the data of both 18S rDNA and rbcL cpDNA. In our analysis of phylogenetic relationships within the genus Closterium, the existing strains formed 14 clades (species complexes). Within some complexes, some strains don’t differ phenotypically, but diverge on the phylogenetic tree, which indicates a hidden taxonomic diversity within the genus.

Separating the impact of work environment and machine operation on harvester performance

In mechanized logging operations, interactions between the forest machines and their operators, forest resources and environmental conditions are multifold and not easily detected. However, increased computational resources and sensing capabilities of the forest machines together with extensive forest inventory data enable modeling of such relationships, leading eventually to better planning of the operations, better assistance for the forest machine operators, and increased efficiency of timber harvesting. In this study, both forest machine fieldbus data and forest inventory data were acquired extensively. The forest inventory data, acquired nationwide, was clustered to categorize general tree and soil types in Finland. The found forest categories were applied when the harvester fieldbus data, collected from the forest operations in the North Karelia region with two similar harvesters, was analyzed. When the performance of the machine and the operator, namely the fuel consumption and log production, is studied individually for each forest cluster, the impact of working environment no longer masks the causes based on the machine or the operator, thus making the observations from separate forest locations comparable. The study observed statistically significant differences in fuel consumption between the most general tree and soil clusters as well as between the harvester-operator units. The modeling approach applied, based on multivariate linear regression, finds such reasons for the differences that have clear interpretation from machine setup or operator working style perspective, and thus offers a feasible method for assisting the operators in improving their working practices and thus the overall performance specifically at forest of given type.

Field Identification of Citrus Canker Symptoms and Decontamination Procedures

Citrus canker, caused by a bacterial pathogen Xanthomonas axonopodis pv. citri, is a serious disease of most citrus varieties. The disease causes necrotic lesions on leaves, stems, and fruit (Figure 1 and Figure 2). Severe infestation can cause defoliation, premature fruit drop, twig dieback, general tree decline, and very bad blemishes on fruit. Trees infected with citrus canker become weak, unproductive, and unprofitable. This document is PP-214, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date October 2005. PP-214/PP136: Field Identification of Citrus Canker Symptoms and Decontamination Procedures (ufl.edu)

Asymptotic frequency of shapes in supercritical branching trees

The shapes of branching trees have been linked to disease transmission patterns. In this paper we use the general Crump‒Mode‒Jagers branching process to model an outbreak of an infectious disease under mild assumptions. Introducing a new class of characteristic functions, we are able to derive a formula for the limit of the frequency of the occurrences of a given shape in a general tree. The computational challenges concerning the evaluation of this formula are in part overcome using the jumping chronological contour process. We apply the formula to derive the limit of the frequency of cherries, pitchforks, and double cherries in the constant-rate birth‒death model, and the frequency of cherries under a nonconstant death rate.