Phylogenetic analysis of the tribe Bovini (Mammalia: Artiodactyla)

A matrix of 57 (mainly cranial) characters and 32 taxa of fossil and Recent Bovini (buffaloes, bison and cattle) has been analysed using the parsimony program HENNIG86. Among the best established results are the exclusion of Parabos , polyphyly of Leptobos , monophyly of the Bos sensu lato + buffaloes group (a clade including all Recent Bovini), probable monophyly of the Bubalina and Syncerina, and the close relationship between bison and yak. Some other interesting questions raised include the apparent absence of a close link between Pliocene African bovines (except "Leptobos" syrticus ) and later African buffaloes, and the possible monophyly of Pelorovis oldowayensis+Bos sensu lato .     

THE ORGANIZATION AND EVOLUTION OF MICROTUBULAR ORGANELLES IN CILIATED PROTOZOA

(1) Ciliated protozoa are viewed as unicellular organisms structured in a hierarchy of organizational levels that include the macromolecular, suborganellar, unit organellar, organellar complex, and organellar system. (2) The ciliate cortex is divided into two major functional regions, the somatic region and the oral region. The fundamental component of the cortex is an organellar complex, the kinetid, whose organizing centre is the kinetosome with which are associated three fibrillar associates diagnostic of ciliates. These three fibrillar associates are the periodically striated kinetodesmal fibril and two microtubular ribbons, the transverse and postciliary ribbons. (3) Somatic and oral kinetids are found to be of three major types: monokinetids are composed of one kinetosome and its fibrillar associates; dikinetids are composed of two kinetosomes and their fibrillar associates; polykinetids are composed of more than two kinetosomes and their fibrillar associptes. (4) The mechanisms underlying kinetid function and development remain largely unexplored. Research into the molecular biology and ultrastructure, especially of mutant forms, should provide basic insights in the near future. (5) The conservation of kinetid structure across major phyla of organisms suggests that this subcellular structure should be useful in phylogenetic analysis despite the concepts of ‘chemical identity’ and ‘organic design’. (6) The evolutionary rate of change of oral features is greater than that of somatic features, probably due to developmental and ecological factors. Nevertheless both cortical regions are constrained by the phenomenon of structural conservatism; that is, the conservation of structure through time is inversely related to the level of biological organization. (7) Eight major groupings of ciliate species are recognized, based on ultrastruc-tural features of the cortex. Several examples of differences between these eight groups and the groups presently recognized are discussed.     

Effects of the nematicide oxamyl on life cycle stages of Globodera rostochiensis

Hatched second stage juveniles of Globodera rostochiensis were found to be more sensitive than either unhatched juveniles or adult males to low concentrations of oxamyl (EC₅₀ value for activity 0.5 μg oxamyl ml^-1). Development of juveniles in roots was significantly inhibited by 2.0 μg oxamyl ml^-1 probably due to impairment of normal feeding activity. The behavioural events necessary for orientation of juveniles towards roots for invasion and orientation of males towards females for fertilisation were found to be impaired by 0.5 and 1.0 μg oxamyl ml^-1 respectively. A comparison with previous work on Meloidogyne incognita showed G. rostochiensis juveniles to be more sensitive to oxamyl.     

Interactions Between Physical and Biological Constraints in the Structure of the Inflorescences of the Araceae

A study of the inflorescences ofMonsteraandAnthuriumwas usedto establish a relationship between biological and physicalconstraints for the structure of plant organs. The physicalconstraint between flowers in the compact inflorescences ofAnthuriumandMonsteraisexpressed by Aboav-Weaire's law. The application of this lawto inflorescences indicates a linear relationship between thenumber of sides of a flower and the number of sides of neighbouringflowers. However, the slope of this straight line is significantlyhigher forAnthuriumandMonsterathan that expected in theory.This deviation from the law is attributable to a biologicalcause that can be estimated using Aboav-Weaire's law. Actingalone, the biological constraint tends to produce four-sidedflowers. The equilibrium between biological and physical constraintsreduces the number of sides per flower from six (theoreticalvalue) to 5.9 (inAnthurium) or 5.8 (inMonstera) with a varianceof the measures less than that expected in theory. Furthermore,when flower density in an inflorescence increases (towards themiddle of the inflorescence inMonsteraand towards the lowersection forAnthurium) the number of sides approaches six (i.e.the physical constraint dominates). When flower density decreases(towards the top of the inflorescence) the number of sides approaches5.5 (i.e. the biological constraint dominates). The geometryof the inflorescences ofAnthuriumandMonsterais the result ofthe joint action of biological and physical constraints.Copyright1998 Annals of Botany Company Monstera,Anthurium, Araceae, Aboav-Weaire, inflorescence, constraint, flower.