Growth models and the expected distribution of fluctuating asymmetry

Multiplicative error accounts for much of the size-scaling and leptokurtosis in fluctuating asymmetry. It arises when growth involves the addition of tissue to that which is already present. Such errors are lognormally distributed. The distribution of the difference between two lognormal variates is leptokurtic. If those two variates are correlated, then the asymmetry variance will scale with size. Inert tissues typically exhibit additive error and have a gamma distribution. Although their asymmetry variance does not exhibit size-scaling, the distribution of the difference between two gamma variates is nevertheless leptokurtic. Measurement error is also additive, but has a normal distribution. Thus, the measurement of fluctuating asymmetry may involve the mixing of additive and multiplicative error. When errors are multiplicative, we recommend computing log  E ( l ) − log  E ( r ), the difference between the logarithms of the expected values of left and right sides, even when size-scaling is not obvious. If l and r are lognormally distributed, and measurement error is nil, the resulting distribution will be normal, and multiplicative error will not confound size-related changes in asymmetry. When errors are additive, such a transformation to remove size-scaling is unnecessary. Nevertheless, the distribution of l  −  r may still be leptokurtic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 57–65.     

Fine-Structural Changes Associated with Pseudocyst Formation in Trichomitus batrachorum*

SYNOPSIS. Several fine-structural changes were observed during formation of the so-called pseudocysts of Trichomitus batrachorum grown in an agar-free medium. Among these changes the most frequent were those of the undulating membrane complex. Internalization of the marginal lamella combined with disappearance of the fin-like, membranous dorsal fold occurred with the highest frequency. In many organisms these alterations were accompanied by internalization of the recurrent flagellum, which, however, remained external in other, presumably earlier stages of pseudocyst formation. In some of the internalized and even still external recurrent flagella the microtubules were in various states of disassembly. The often distended flagellar membrane enclosed large accumulations of filaments 5 nm in diameter. Internalization of the anterior flagella also was noted. Changes similar to those characteristic of the recurrent flagella were not seen, however, among the microtubules of the anterior flagella or among those of the pelta or the axostyle.     

Fine Structure of the Mastigont System in Tritrichomonas muris (Grassi)*

SYNOPSIS. Tritrichomonas muris shares many fine-structural details with the previously described members of the family Trichomonadidae, and especially with the organisms belonging to the subfamily Tritrichomonadinae. Among the features which T. muris has in common with all Trichomonadidae and in all probability with other Trichomonadida are the arrangement and structure of: the kinetosomes; many rootlet filaments, including the sigmoid filaments of kinetosome #2; the parabasal apparatus; and the pelta-axostyle complex. The structures which T. muris-type flagellates share with other Tritrichomonadinae, and especially with Tritrichomonas augusta-type species (including T. foetus), but not with Trichomonadinae that have been studied to date, are: the Type A costa; a comb-like structure, which appears to have replaced the costal base of Trichomonadinae and of Hypotrichomonas; the suprakinetosomal body, rudimentary in T. muris; and the infrakinetosomal body. The undulating membrane, like that of T. augusta-type organisms, consists of a proximal and a distal part. The proximal part, which contains the proximal marginal lamella, is less developed in T. muris than in T. augusta-type flagellates, being represented by a relatively low ridge for the entire length of the organism. The distal part of the membrane in T. muris, on the other hand, is more highly developed; it is a heavy cord, with a distal marginal lamella which consists of a large triangular organelle having a highly ordered structure and 2 less well defined cords distal to this organelle. The tubules of the recurrent flagellum occupy the area distal to the cords. The sigmoid filaments of kinetosome #2, unlike those of other Trichomonadidae examined to date, extend posteriorly to the peltar-axostylar junction; they seem to terminate within the cytoplasm near, but not connected to the axostyle. In addition to the Type A costa, there is a small rootlet filament, which appears to be homologous to the rudimentary costa noted in Hypotrichomonas. Some of the paraxostylar and paracostal granules consist of an outer, relatively dense layer and an inner “core” of moderate density; between the 2 there is a lucent ring. The discussion deals in some detail with the possible nature of the paraxostylar and paracostal granules in trichomonads. The taxonomic status of Tritrichomonas cricetus (Wantland) [Tritrichomonas criceti (Wantland) emend. Levine] and Trichomonas criceti Ray & Sen Gupta is discussed in an appendix; it is concluded that both of these names are synonyms of T. muris (Grassi).     

Phylogenetic relationships and molecular evolution in uropeltid snakes (Serpentes: Uropeltidae): allozymes and albumin immunology

Multilocus electrophoretic methods and microcomplement fixation comparisons of serum albumin are used to assess phylogenetic relationships among species of uropeltid snakes, to infer aspects of their population biology and biogeography, and to evaluate their relationships to other primitive snakes (Henophidia). There is very good agreement between phylogenetic inferences derived from the electrophoretic data and those derived from the albumin immunological data. Protein variation detected by electrophoresis is relatively high among 17 operational taxonomic units (OTUs) examined. The mean number of alleles per locus (5.1 across all OTUs), levels of polymorphism (25% of loci), and heterozygosity (4–6%), are typical of, or greater than, values reported for other snakes. Species of uropeltids are genetically highly differentiated, as measured by genetic distances (lowest interspecific Nei's unbiased genetic distances, 0.22-0.27 among several Sri Lankan species; 2.3 between Teretrurus of India and other uropeltines). The phylogenetic tree most consistent with both the immunological and electrophoretic data shows uropeltines from Sri Lanka to be monophyletic, but the Indian species are paraphyletic with respect to those from Sri Lanka. Rhinophis travancoricus of India is inferred to be the sister taxon to the Sri Lankan radiation. As the genera are presently understood, neither Rhinophis nor Uropeltis appears to be monophyletic. A biogeographic scenario derived from the phylogenetic hypothesis suggests an early diversification of uropeltids in India, followed by a single invasion into the lowlands of Sri Lanka. Subsequent evolution on Sri Lanka resulted in occupation of montane biotopes. Cylindrophis is the sister group to uropeltines and is considered a member of the Uropeltidae. The immunological data indicate no phylogenetic association between uropeltids and other ‘anilioid’ taxa, specifically Anilius, Loxocemus or Xenopeltis, although we cannot rule out a very remote relationship. We specifically reject the hypothesis that uropeltines and scolecophidians form a clade relative to henophidians. High levels of genetic variation and a trend toward negative F_IS values for polymorphic loci in three populations suggest generally large effective population sizes and outbreeding in these species. The niche-width variation hypothesis for allozyme loci is not supported by the uropeltid data. In comparison to other vertebrates, the relationship between Nei's genetic distance and albumin immunological distance in uropeltids suggests either conservative albumin evolution or strong differentiation at electrophoretic loci.     

Nine-year reciprocal transplant experiment in the gardens of the basin and mountain big sagebrush (Artemisia tridentata: Asteraceae) hybrid zone of Salt Creek Canyon: the importance of multiple-year tracking of f itness

We have studied reciprocal transplant gardens involving the hybrid zone between basin and mountain big sagebrush ( Artemisia tridentata ) in Salt Creek Canyon, Utah, for 9 years. Previously, we showed that the parental taxa and hybrids had superior reproductive and vegetative performance in their native garden. These earlier data supported the Bounded Hybrid Superiority model. Now, after 9 years, we find that the mountain seed source plants have greater relative fitness than middle hybrid zone seed source plants in the middle hybrid zone garden. These results may be due to plant density and climatic factors more conducive to mountain seed source growth than that of either basin or middle hybrid zone seed source plants. On the other hand, these fitness estimates do not take into account the timing of reproduction, which together with the age-specific survival rate, can profoundly affect lifetime fitness. The intrinsic rate of increase ( r ) takes both of these factors into account, providing another estimate of fitness. Middle hybrid zone seed source plants had the greatest rate of increase in both the middle hybrid zone and mountain gardens and a greater rate of increase than either parent in the basin garden. This is most likely due to the greater reproductive performance of middle hybrid zone plants earlier in life than either parental taxon. These results partly support the Bounded Hybrid Superiority model and show the importance of long- term studies of hybrid fitness.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 213–225.     

Structure of Hypotrichomonas acosta (Moskowitz) (Monocercomonadidae,Trichomonadida) as Revealed by Electron Microscopy*

SYNOPSIS. The fine structure of Hypotrichomonas acosta resembles in many respects that of Trichomonadidae, and especially of members of the sub-family Trichomonadinae which have been examined to date by electron microscopy. In addition, the flagellate has certain ultrastructural differences from the latter organisms, some of which are of phylogenetic significance. Among these, the structure of the undulating membrane and the apparently occasional presence of a fine filament which may be considered as homologous to the costa of Trichomonadidae are the most important. The undulating membrane is represented by a rather low and otherwise poorly developed dorsal cytoplasmic fold with an ill-defined distal marginal lamella; the recurrent flagellum is applied near the dorsum of the fold. In a very few preparations a relatively short filament, of a diameter falling below the resolution limits of light microscope, is seen in a position which corresponds to that of the costa of Trichomonadidae. The identity of the filament as a probable rudimentary costa is supported also by the character of its periodicity. The rare appearance of the rudimentary costa among hundreds of sections may be explained either by its minute dimensions or by its absence from many hypotrichomonads. Other structures recorded for the first time in trichomonads are: the fine filamentous connections of the axostylar microtubules; the branching of parabasal filament 2; and the unusually organized, perhaps helical, polysomes, which are found in addition to the ribosomal complexes associated with the endoplasmic reticulum and commonly found in trichomonads. A detailed analysis of interconnections among various mastigont structures is presented and several kinds of cytoplasmic inclusions are described. H. acosta is of interest in the study of the nuclear envelope and presence of nuclear pores, which are numerous and conspicuous in this flagellate. The fine structure of the hypotrichomonad is discussed in relation to that of other trichomonads and in some instances to that of other protozoa.     

Structure of Monocercomonas sp. as Revealed by Electron Microscopy*

SYNOPSIS. Monocercomonas shares many fine-structural features with all other trichomonads. These include the basic arrangement of the kinetosomes as well as of the recurrent and 3 anterior flagella. The pelta-axostyle complex and the parabasal apparatus, i.e. the Golgi complex and the periodic filaments, also conform to the trichomonad pattern. Of interest with regard to the crucial evolutionary position of Monocercomonas, considered to represent the most primitive trichomonad type, is the fact that it has some structures in common with other Monocercomonadidae and Trichomonadinae and others in common with Devescovinidae and Tritrichomonadinae. Among the former organelles are the marginal lamella and the costal base, and among the latter, the comb-like organelle situated between the infrakinetosomal body and parabasal filament 2 as well as the infrakinetosomal body. No traces of either costa or undulating membrane have been noted, but a complex structure homologous to the marginal lamella of Hypotrichomonas and Trichomonadinae is found underlying the short anteriormost portion of the recurrent flagellum that is attached to the body surface. Observations of sections of selected division stages indicate the potential of parental kinetosomes #1 and #3 to become daughter kinetosome #2.