Character of distribution of defects of wing venation in the banded agrion (Calopteryx spendens)

The distribution of morphological structures was studied in wings of the banded agrion (Calopteryx splendens Harr.) from different intrapopulation groups. Dragon flies of odd years of emergence are characterized by a more stable pattern of ontogenetic processes accordin to the mean total number of venation defects. The sharply increased level of radiation in summer 1986, which coincided with the flight of dragon-flies, could have caused hereditary defects expressed in a sequence of generations of even years of emergence. Apparently, most alternative features of wing venation in dragon-flies can be considered as markers of stability of the ontogenetic processes, which reflect, to a great extent, genotypic features of the organisms in a population. A possible mechanism has been described, which explains the proposed topological model of formation of the venation defects of different types. The increase in mean frequencies of defects can suggest an enhanced development over the aberrant epigenetic trajectories, which may lead to the elimination of these organisms under the influence of various agents, i.e., to the stabilizing selection in a population. The results obtained suggest that defects of venation arise on the stochastic basis and their frequency increases upon destabilization of ontogenetic processes not only by the environmental factors, but also by genetic stress. Venation defects can be successfully used in population biomonitoring.     

Density-dependent population dynamics in larvae of the dragonfly Pachydiplax longipennis: a field experiment

Summary Several features of dragonfly population biology suggest that population regulation occurs in the larval stage. This study was designed to determine if density-dependent interactions among larval odonates can affect survival, growth and emergence. First-instar larvae of the dragonfly Pachydiplax longipennis were raised in outdoor experimental ponds at initial densities of 38, 152, and 608 larvae · m^-2, under two levels of food availability. Food availability was supplemented in half the pools by volumetric addition of zooplankton every other day. Pools in the low food treatment did not receive the zooplankton supplement.There was a strong negative effect of density on the mean growth rate of survivors, which included both emerging tenerals and individuals overwintering in the larval stage. A higher proportion emerged from low density than high density pools. Metamorphs from high density populations were smaller and emerged slightly later than those from low density, but the absolute number of metamorphs did not differ significantly among density treatments. Food supplementation significantly increased the proportion of overwintering larvae. There were no significant food-by-density interactions, indicating that food and density acted independently on larval population dynamics. Density-dependent mechanisms can clearly contribute to odonate population regulation, especially by controlling the number of larvae which emerge and the average age at reproduction. Population-level responses to density may be a result of interference among larvae.     

Adult emergence phenology in checkerspot butterflies: the effects of macroclimate,topoclimate, and population history

The prediction of adult emergence times in insect populations can be greatly complicated by microclimatic gradients, especially in circumstances where distributions of juveniles along those gradients vary from year to year. To investigate adult emergence patterns in topographically heterogeneous habitats, we built a model of postdiapause development of the Bay checkerspot butterfly, Euphydryas editha bayensis. The model uses slope-specific insolation as the rate-controlling variable, and accounts for both solar exposure of the habitat and cloud cover. Instar-specific larval mass gains per unit of insolation were determined from mark-recapture experiments. A small correction for daily low temperatures was used to calibrate the model to five years of field data on larval mass. The model predicted mean mass of 90% of larval samples within 4 clear days over a 70–120 day growing season. The magnitude of spatial variation in emergence times across habitat slopes is greater than annual variation in emergence times due to yearly weather conditions. Historical variation (yearly shifts in larval distributions across slopes) is an important determinant of mean population emergence dates. All of these factors need to be considered in understanding adult emergence phenology in this butterfly and in other insects inhabiting heterogeneous thermal environments. Such an understanding can be useful in managing insect populations for both pest control and conservation.     

Fluctuating asymmetry in the honey bee,Apis mellifera: effects of ploidy and hybridization

We present a new measure of morphological asymmetry that avoids most of the statistical problems inherent in character-by-character analysis of size or shape. The method is an application of Procrustes analysis, which computes best-fitting super-positions of configurations of landmarks to the left and right sides of a single specimen. The Procrustes method combines subtle deviations in all aspects of the landmark configuration into one net asymmetry score. Directional asymmetry is separated from fluctuating asymmetry in a simple partition of a net sum-of-squares, and geometrical details of either component can be inspected by traditional methods of multivariate statistical analysis of landmarks. We demonstrate this method in a comparison of wing venation asymmetry in male (haploid) and female (diploid) honey bees (Apis mellifera). In addition we investigate the effects of ploidy and inter-subspecies hybridization on asymmetry and wing venation abnormalities, using the subspecies A. m. mellifera, A. m. carnica, and the hybrid strain “Nigra”. Results suggest that while the haploid males showed a higher frequency of wing venation abnormalities and greater total asymmetry than the diploid females, most of the asymmetry difference between males and females was in the form of directional, not fluctuating, asymmetry. Hybrid females had a higher frequency of wing venation abnormalities than females of either subspecies, but there were no significant differences in the mean level of asymmetry among females of A. m. mellifera, A. m. carnica and hybrid Nigra. Hybrid males had higher absolute frequency of wing venation abnormalities and asymmetry than males of either subspecies. However the mean frequency of venation abnormalities did not differ significantly between Nigra and A. m. carnica males, and mean asymmetries were not significantly different between Nigra and A. m. mellifera males. We discuss the relationship which is assumed to exist between developmental stability and fluctuating asymmetry in light of our result.     

INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: STIPULATE LEAVES OF THE RUBIACEAE INCLUDING A PROBABLE POLYPLOID POPULATION

A comparative study was made of the gross morphology, fine venation and cuticular features of Leitneria fioridana Chapman, the single living representative of the order Leitneriales and Leitneria eocenica (Berry) Brown, presumbaly a related fossil species. In addition to the type material, newly collected fossil specimens were investigated from clay pits in the Middle Eocene, Claiborne Formation, of western Tennessee and Kentucky. Foliate stipules attached to the petioles of several specimens suggest the assignment of this fossil leaf type to the genus Leitneria is incorrect. The nature of the gross morphology, fine venation and cuticular features confirms the misidentification. Previously, various specimens of this fossil leaf type have been placed in eight species of seven genera in seven families of six angiosperm orders, none of which are correct systematically. The gross morphology, venation and cuticular characters of the fossil leaf are distributed among a few extant South American genera of arborescent Rubiaceae. The fossil is an extinct rubiaceous leaf type which cannot be placed within a single modern subfamily, tribe or genus of the family. The organ genus, Paleorubiaceophyllum is proposed for these leaves. Three varieties of a single fossil species, P. eocenicum, are recognized. One variety with epidermal cells nearly twice the size of the others may represent a polyploid population.     

Linking evolution and development: Synchrotron Radiation X‐ray tomographic microscopy of planktic foraminifers

Abstract: Making the link between evolutionary processes and development in extinct organisms is usually hampered by the lack of preservation of ontogenetic stages in the fossil record. Planktic foraminifers, which grow by adding chambers, are an ideal target organism for such studies as their test incorporates all prior developmental stages. Previously, studies of development in these organisms were limited by the small size of their early chambers. Here, we describe the application of synchrotron radiation X‐ray tomographic microscopy (SRXTM) to document the ontogenetic history of the foraminifers Globigerinoides sacculifer and Globorotalia menardii. Our SRXTM scans permit resolution at submicrometre scale, thereby displaying additional internal structures such as pores, dissolution patterns and complexity of the wall growth. Our methods provide a powerful tool to pick apart the developmental history of these microfossils and subsequently assist in inferring phylogenetic relationships and evolutionary processes.     

The position and growth of lateral roots on cultured root axes of tomato,Lycopersicon esculentum (Solanaceae)

Root axes of tomato (Lycopersicon esculentum) were cultured in vitro in three different concentrations of sucrose in order to vary their growth rate. Lateral root growth and the initiation of lateral root primordia were studied on each group of axes. Various aspects of primordium initiation, positioning, and emergence were quantified with a view to discovering variable and constant features of these processes. Variable parameters were the rate and frequency of root primordium emergence. Constant parameters, at least under the prevailing conditions, were the spacing between successive laterals and primordia, and the position of the primordia in relation to the vascular system. A model of primordium initiation is presented which combines controls determined by the divisional history of the potential primordium cell and by the vascular pattern.Dedicated with great respect to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday in recognition of her distinguished contributions to cytology.     

The role of sexual and clonal reproduction in maintaining population in Fritillaria camtschatcensis (L.) Ker-Gawl. (Liliaceae)

Fritillaria camtschatcensis can reproduce by means of both sexual reproduction and clonal multiplication. Despite prolific seed production, no seedlings have been found for several years in natural populations on Mt Hakusan. The purposes of this paper are to clarify: (i) whether population size is maintained mainly by clonal multiplication; and (ii) if this is the case, to what extent occasional seedling establishment affects population growth rate and population structure. Two permanent quadrats were placed in subalpine meadows in 1992 on Mt Hakusan. Plant size, location and reproductive states for all ramets in the quadrats were recorded every year. Projection matrices were created based on field census, and computer simulation experiments were performed. Fritillaria camtschatcensis had two types of flower, male flower and cosexual flower, and they were changeable. This is the first report on sex lability in Fritillaria. Clonal growth was more closely correlated with life-history stages, especially with sexual states than with plant size. The population growth rate, , was 1.006 for the Mizuyajiri population and 1.047 for the Nanryu population, respectively. Seedlings were found in 1996 for the first time. These facts indicate that populations of F. camtschatcensis on Mt Hakusan can usually be maintained by clonal multiplication. However, it is not yet certain whether seeds germinate every year or whether a flush of seedling emergence occurs once in every few years in natural populations. Computer simulation revealed that: (i) there was a critical germination rate above which population growth rate suddenly increased; and (ii) occasional seedling establishment could provide almost the same contribution to population growth rate as that of annual seedling establishment. These results suggest that population size can be maintained mainly by clonal multiplication, and the role of sexual reproduction lies beyond maintaining the population size in F. camtschatcensis.     

A study of the activity of enzymes of the antioxidant system in ontogenesis ofArabidopsis thaliana mutants tolerant to norflurazone

The activities of superoxide dismutase and guaiacol-dependent peroxidase were studied in the ontogenesis of recessive homozygous mutants ofArabidopsis thaliana Heynh.le-2 andnfz24, which are characterized by two- to threefold increases in tolerance to the herbicide norflurazone. The mutantsle-2 andnfz24 differed from the initial race Dijon in some phenotypic features, duration of ontogenetic stages, and dynamics of the superoxide dismutase and peroxidase activities in ontogenesis. A single treatment of plants with norflurazone induced an accelerated increase in the level of both enzymes in the mutants as compared to the wild type plants. Under the conditions of multiple treatment with norflurazone, the mutantsle-2 andnfz24 displayed a higher tolerance to the bleaching effect of the herbicide and were characterized by a higher level of superoxide dismutase. The data obtained suggest that the superoxide dismutase and peroxidase activities are controlled by both ontogenetic factors and stress signals. Mutations in the linesle-2 andnfz24 increase sensitivity to a stress signal or increase efficiency of an adaptive response due to long-term maintenance of a high level of the antioxidant enzymes under the conditions of stress.     

Experimental analysis of character coupling across a complex life cycle: Pigment pattern metamorphosis in the tiger salamander,Ambystoma tigrinum tigrinum

Developmental relationships among characters are expected to bias patterns of morphological variation at the population level. Studies of character development thus can provide insights into processes of adaptation and the evolutionary diversification of morphologies. Here I use experimental manipulations to test whether larval and adult pigment patterns are coupled across metamorphosis in the tiger salamander, Ambystoma tigrinum tigrinum (Ambystomatidae). Previous investigations showed that the early larval pigment pattern depends on interactions between pigment cells and the lateral line sensory system. In contrast, the results of this study demonstrate that the major features of the adult pigment pattern develop largely independently of both the early larval pattern and the lateral lines. These results suggest that ontogenetic changes that occur across metamorphosis decouple larval and adult pigment patterns and could thereby facilitate independent evolutionary modifications to the patterns during different stages of the life cycle. J. Morphol. 237:53–67, 1998. © 1998 Wiley-Liss, Inc.     

Influence of energetic status on ontogenetic niche shifts: emergence from the redd is linked to metabolic rate in brown trout

Ontogenetic niche shift should occur when the ratio of growth opportunities to mortality risk becomes higher in the subsequent habitat. While most studies have focused on size to understand the timing of these shifts, an endogenous factor like energetic status (interaction between energy available and energy requirements) appears as a natural candidate to integrate and analyze the growth trade-off between habitats. In this study, we measure energetic content and metabolic rate of individual brown trout (Salmo trutta) fry at emergence from gravel to investigate the influence of energetic status on the timing of this critical ontogenetic niche shift. In addition, as offspring energetic status is subject to parental effects, we examine how females could maximize their own fitness by influencing offspring emergence timing. Our results demonstrate that emergence from gravel is influenced by energetic status. Individuals that emerge first have a higher energetic content but deplete it faster because of a higher metabolic rate. We also find that female fecundity is positively related to emergence period duration. Moreover, our results suggest that females may decrease kin competition during the critical period of emergence by influencing the energetic status of offspring, thus, maximizing their own fitness. Our results help elucidate the mechanisms underlying early ontogenetic niche shifts in juvenile fish and suggest reasons why maternal investment can be so variable within populations.     

贺兰山岩黄耆及其近缘种的分类学研究

依据植物野外和腊叶标本形态观察以及小叶脉序观察,对贺兰山岩黄耆(豆科)及其近缘种进行了分类学研究。结果表明:贺兰山岩黄耆及其近缘种之间较为稳定的差别体现在花器官的形态方面。贺兰山岩黄耆与短翼岩黄耆的主要区别特征是小苞片长为萼筒的1～2倍,旗瓣与龙骨瓣近等长,而后者的小苞片长为萼筒的0.5～0.8倍,旗瓣长为龙骨瓣的0.8倍。贺兰山岩黄耆与华北岩黄耆和费尔干岩黄耆的主要区别是翼瓣长为龙骨瓣的0.3～0.5倍,而后二者的翼瓣长均为龙骨瓣的0.7～0.8倍。在小叶脉序特征方面,贺兰山岩黄耆与短翼岩黄耆和华北岩黄耆近似,均为小叶一级脉纤细,二级脉不分支,二级脉环外有较多网结三级脉,具少量复合二级间脉或不明显,而费尔干岩黄耆小叶一级脉粗,二级脉多分支,二级脉环外有少量网结三级脉,具明显的简单二级间脉。此外,小叶脉序特征可能在岩黄耆属组间关系的探讨中发挥作用。     

The subcommissural organ of the adult and pouch-young brush-tailed possum (Trichosurus vulpecula)

Summary Scanning electron microscopy (SEM) was used to examine the surface features of the subcommissural organ (SCO) and the roof of the cerebral aqueduct of 35 adult and 33 pouch-young Trichosurus vulpecula. The animals were at various developmental stages and of both sexes. In the adult animals, the surfaces of the groove and the adjacent medial walls of the ridges of the SCO were characterized primarily by microvilli. Typically, Reissner's fibre was associated closely with the median groove of the SCO. The ridges and the paramedian grooves of the SCO were often heavily ciliated displaying many cerebrospinal fluid-contacting nerve processes. These processes were of varying lengths with terminal and preterminal varicosities. The observed morphology supports a hypothesis suggesting that under certain physiological and pathological conditions the flow of CSF may be directed away from the heavily ciliated ridges to the poorly ciliated groove containing the Reissner's fibre. In the youngest pouch-young animals there were no cilia, CSF-contacting nerve processes, nor supraependymal cells. Also the surface features of the SCO in the young assumed adult appearance before the adjacent roof of the cerebral aqueduct. These findings suggest the possibility that the SCO begins to function early in ontogenetic development. Acknowledgement. Technical assistance of Mrs. G. Hermanis is gratefully acknowledged.The author thanks the Director of Wild Life and National Parks, South Australia, for permission to use brush-tailed possums     

Continuity and/or Discontinuity in the Pleistocene peopling of Europe?

Today, a number of European fossils are known which can be dated between 500,000 and 900,000 years ago. These remains provide evidence of an early human settlement of Europe, which apparently predates the emergence of Neanderthals. However, the taxonomic attribution of these fossils and their phylogenetic relationship to each other and to Neanderthals remains unclear. Evidence for a direct phylogenetic relationship with Neanderthals or a discontinuity is not yet conclusive. The task is complicated by the fact that the emergence of the Neanderthal population was not abrupt, but progressive. It is probable that the peopling of Europe during the entire Pleistocene was unique and presented from its very origins an “endemic” (a cul-de-sac) character, which may explain that the first traces of fossils in Europe illustrate particularities in comparison those from Africa and from Asia. Further paleontological discoveries will be needed to redefine the status of these features and to improve our understanding of human evolution in Europe.     

Systems analysis of density-dependent population processes in the azuki bean weevil,Callosobruchus chinensis

Systems analysis of density-dependent population processes was conducted in an experimental population of the azuki bean weevil,Callosobruchus chinensis. Density-dependent population change was formulated for two separate processes; adult production of eggs and hatching of the eggs outside the beans, and survival of the first instar larvae inside the beans and their emergence as new adults. The formulation of each process was based on a common basic equation modified from the logistic-difference equation. Parametric values were estimated from experimental data onC. chinensis in a laboratory population. Simulations of the model showed good fits not only to observed population changes both outside and inside the beans, but also to the observed reproduction curve reflecting the population change as a whole within one generation in an experimental population. Furthermore, population dynamics from generation to generation were simulated from the model reproduction curve. The simulation showed a slight dumped oscillation and converged to a carrying capacity, which fitted well with the experimental population dynamics.     

Neoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturus alpestris (Amphibia: Caudata)

Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two distinct processes can lead to paedomorphosis in the Alpine newt, Triturus alpestris. In this respect, we compared age structures of paedomorphic and metamorphic individuals in two newt populations where the two forms lived syntopically. Whereas paedomorphosis resulted in a slower rate of somatic development in one population, it resulted in an acceleration of sexual maturation in the other population. These processes correspond to neoteny and progenesis, respectively. These results suggest that phenotypic plasticity can result from contrasted ontogenetic pathways between two populations of the same species. They give support to models that consider gonadic development as the target of selection under different environmental pressures.     

Appendicular skeletal morphology in minute salamanders,genus Thorius (amphibia: Plethodontidae): Growth regulation,adult size determination,and natural variation

Patterns of growth and variation of the appendicular skeleton were examined in Thorius, a speciose genus of minute terrestrial plethodontid salamanders from southern Mexico. Observations were based primarily on ontogenetic series of each of five species that collectively span the range of adult body size in the genus; samples of adults of each of seven additional species provided supplemental estimates of the full range of variation of limb skeletal morphology. Limbs are generally reduced, i.e., pedomorphic, in both overall size and development, and they are characterized by a pattern of extreme variation in the composition of the limb skeleton, especially mesopodial elements, both within and between species. Fifteen different combinations of fused carpal or tarsal elements are variably present in the genus, producing at least 18 different overall carpal or tarsal arrangements, many of which occur in no other plethodontid genus. As many as four carpal or tarsal arrangements were observed in single population samples of each of several; five tarsal arrangements were observed in one population of T. minutissimus. Left-right asymmetry of mesopodial arrangement in a given specimen is also common. In contrast, several unique, nonpedomorphic features of the limb skeleton, including ossification of the typically cartilaginous adult mesopodial elements and ontogenetic increase in the degree of ossification of long bones, are characteristic of all species and distinguish Thorius from most related genera. They form part of a mechanism of determinate skeletal growth that restricts skeletal growth after sexual maturity. Interspecific differences in the timing of the processes of appendicular skeletal maturation relative to body size are well correlated with interspecific differences in mean adult size and size at sexual maturity, suggesting that shifts in the timing of skeletal maturation provide a mechanism of achieving adult size differentiation among species. Processes of skeletal maturation that confer determinate skeletal growth in Thorius are analogous to those typical of most amniotes – both groups exhibit ontogenetic reduction and eventual disappearance of the complex of stratified layers of proliferating and maturing cartilage in long bone epiphyses – but, unlike most amniotes, Thorius lacks secondary ossification centers. Thus, the presence of secondary ossification centers cannot be used as a criterion for establishing determinate skeletal growth in all vertebrates.     

Patterns of intraspecific variation through ontogeny: a case study of the Cretaceous nautilid Eutrephoceras dekayi and modern Nautilus pompilius

The magnitude and ontogenetic patterns of intraspecific variation can provide important insights into the evolution and development of organisms. Understanding the intraspecific variation of organisms is also a key to correctly pursuing studies in major fields of palaeontology. However, intraspecific variation has been largely overlooked in ectocochleate cephalopods, particularly nautilids. Furthermore, little is known regarding the evolutionary pattern. Here, we present morphological data for the Cretaceous nautilid Eutrephoceras dekayi (Morton) and the modern nautilid Nautilus pompilius Linnaeus through ontogeny. The data are used to describe conch morphology and to elucidate the evolutionary patterns of intraspecific variation. We discovered a similar overall pattern of growth trajectories and the presence of morphological changes at hatching and maturity in both taxa. We also found that intraspecific variation is higher in earlier ontogeny than in later ontogeny in both taxa. The high variation in earlier ontogeny may imply increased flexibility in changing the timing of developmental events, which probably played an important role in nautilid evolution. We assume that the decrease in variation in later ontogeny reflects developmental constraints. Lastly, we compared the similarity/dissimilarity of ontogenetic patterns of variation between taxa. Results reveal that the similarity/dissimilarity of the ontogenetic pattern differs between E. dekayi and N. pompilius. We conclude that this shift in the ontogenetic pattern of variation may be rooted in changes in the developmental programme of nautilids through time. We propose that studying ontogenetic patterns of intraspecific variation can provide new insights into the evolution and development of organisms.     

The costae presenting in high-temperature-induced <Emphasis Type="Italic">vestigial</Emphasis> wings of <Emphasis Type="Italic">Drosophila</Emphasis>: implications for anterior wing margin formation

It has long been noted that high temperature produces great variation in wing forms of the vestigial mutant of Drosophila. Most of the wings have defects in the wing blade and partially formed wing margin, which are the result of autonomous cell death in the presumptive wing blade or costal region of the wing disc. The vestigial gene (vg) and the interaction of Vg protein with other gene products are well understood. With this biochemical knowledge, reinvestigations of the high-temperature-induced vestigial wings and the elucidation of the molecular mechanism underlying the large-scale variation of the wing forms may provide insight into further understanding of development of the wing of Drosophila. As a first step of such explorations, I examined high-temperature-induced (29°C) vestigial wings. In the first part of this paper, I provide evidences to show that the proximal and distal costae in these wings exhibit regular and continuous variation, which suggests different developmental processes for the proximal and distal costal sections. Judging by the costae presenting in the anterior wing margin, I propose that the proximal and distal costal sections are independent growth units. The genes that regulate formation of the distal costal section also strongly affect proliferation of cells nearby; however, the same phenomenon has not been found in the proximal costal section. The distal costal section seems to be an extension of the radius vein. vestigial, one of the most intensely researched temperature-sensitive mutations, is a good candidate for the study of marginal vein formation. In the second part of the paper, I regroup the wing forms of these wings, chiefly by comparison of venation among these wings, and try to elucidate the variation of the wing forms according to the results of previous work and the conclusions reached in the first part of this paper, and provide clues for further researches.