Roy A. Norton

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A century ago, Antonio Berlese first discussed the close phylogenetic relationship between the large mite groups Oribatida and Astigmata. Since then, information having phylogenetic value has greatly increased and the paradigms within which we interpret it have changed. Herein I refine the general hypothesis that Astigmata originated within oribatid mites(More)
Alkaloids in the skin glands of poison frogs serve as a chemical defense against predation, and almost all of these alkaloids appear to be sequestered from dietary arthropods. Certain alkaloid-containing ants have been considered the primary dietary source, but dietary sources for the majority of alkaloids remain unknown. Herein we report the presence of(More)
The stereochemistry of several sterol precursors and end products synthesized by two fungal-like micro-organisms Prototheca wickerhamii (I) and Dictyostelium discoideum (II) have been determined by chromatographic (TLC, GLC, and HPLC) and spectral (UV, MS, and 1H NMR) methods. From I and II the following sterols were isolated from the cells: cycloartenol,(More)
The dominance of sexual reproduction is still an unresolved enigma in evolutionary biology. Strong advantages of sex have to exist, because only a few parthenogenetic taxa persist over evolutionary timescales. Oribatid mites (Acari) include outstanding exceptions to the rule that parthenogenetically reproducing taxa are of recent origin and doomed to(More)
Theories on the evolution and maintenance of sex are challenged by the existence of ancient parthenogenetic lineages such as bdelloid rotifers and darwinulid ostracods. It has been proposed that several parthenogenetic and speciose taxa of oribatid mites (Acari) also have an ancient origin. We used nucleotide sequences of the mitochondrial gene cytochrome(More)
A new fossil site near Gilboa, New York, is one of only three where fossils of terrestrial arthropods of Devonian age have been found. The new Gilboan fauna is younger than the other two but richer in taxa. Fragmentary remains and nearly whole specimens assigned to Eurypterida, Arachnida (Trigonotarbida, Araneae, Amblypygi, and Acari), Chilopoda(More)
Terrestrial fossils that document the early colonization of land are scarce for >100 my after the Cambrian explosion. This raises the question whether life on land did not exist or just did not fossilize. With a molecular dating technique, we analyzed the origin of terrestrial chelicerate microarthropods (Acari, Oribatida) which have a fossil record since(More)
The high incidence of asexuality in oribatid mites presents an unusual opportunity for examining hypotheses for the maintenance of sex. There is a presumed range in age of asexual species: many oribatid species are phylogenetically clustered, occurring in speciose early-derivative families or genera without sexual species, while others are phylogenetically(More)
Astigmata comprise a diverse group of acariform mite species with a remarkable range of life histories, most of which involve parasitic or commensal relationships with other organisms. Several authors have suggested that Astigmata evolved as a paedomorphic clade from within Oribatida, and both morphology and gland-chemistry strongly suggest that their(More)
Frequent convergent evolution in phylogenetically unrelated taxa points to the importance of ecological factors during evolution, whereas convergent evolution in closely related taxa indicates the importance of favourable pre-existing characters (pre-adaptations). We investigated the transitions to arboreal life in oribatid mites (Oribatida, Acari), a group(More)