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Candida albicans, the major human fungal pathogen, undergoes a reversible morphological transition from single yeast cells to pseudohyphal and hyphal filaments (elongated cells attached end-to-end). Because typical C albicans infections contain a mixture of these morphologies it has, for many years, been difficult to assess the relative contribution of each form to virulence. In addition, the regulatory mechanisms that determine growth in pseudohyphal and hyphal morphologies are largely unknown. To address these questions we have generated a C. albicans strain that can be genetically manipulated to grow completely in the hyphal form under non-filament-inducing conditions in vitro. This was achieved by inducing high-level constitutive expression of UME6, a recently identified filament-specific transcriptional regulator of C. albicans hyphal extension. We show that high-level UME6 expression significantly increases hyphal formation and promotes virulence in a mouse model of systemic candidiasis. Our results strongly suggest that shifting the morphology of a C. albicans population toward the hyphal form, and/or increasing hyphal-specific gene expression, during the course of infection is sufficient to improve virulence potential. We also demonstrate that lower levels of UME6 expression specify growth largely in the pseudohyphal form and that increasing UME6 levels is sufficient to cause cells to gradually shift from pseudohyphal to hyphal morphology. In addition, we show that UME6 levels differentially induce the expression of several known filament-specific transcripts. These findings suggest that a common transcriptional regulatory mechanism functions to specify both pseudohyphal and hyphal morphologies in a dosage-dependent manner. filamentous growth | transcriptional regulation

Similarities between Mycobacterium tuberculosis phoP-phoR mutants and the attenuated laboratory strain M. tuberculosis H37Ra in terms of morphological and cytochemical properties, lipid content, gene expression and virulence attenuation prompted us to analyze the functionality of this two-component regulator in the latter strain. Sequence analysis revealed a base substitution resulting in a one-amino-acid change in the likely DNA-binding region of PhoP in H37Ra relative to H37Rv. Using gel-shift assays, we show that this mutation abrogates the ability of the H37Ra PhoP protein to bind to a 40-bp segment of its own promoter. Consistent with this result, the phoP gene from H37Rv but not that from H37Ra was able to restore the synthesis of sulfolipids, diacyltrehaloses and polyacyltrehaloses in an isogenic phoP-phoR knock-out mutant of M. tuberculosis Moreover, complementation of H37Ra with phoP from H37Rv fully restored sulfolipid, diacyltrehalose and polyacyltrehalose synthesis, clearly indicating that the lack of production of these lipids in H37Ra is solely due to the point mutation in phoP. Using a pks2-3/4 knock-out mutant of M. tuberculosis H37Rv, evidence is further provided that the above-mentioned polyketide-derived acyltrehaloses do not significantly contribute to the virulence of the tubercle bacillus in a mouse model of infection. Reasons for the attenuation of H37Ra thus most likely stand in other virulence factors, many of which are expected to belong to the PhoP regulon and another of which, unrelated to PhoP, appears to be the lack of production of phthiocerol dimycocerosates in this strain.

Octocorals, especially gorgonians, are conspicuous on Caribbean coral reefs, but there is no consensus regarding species relationships. Mitochondrial protein-coding genes [NADH-dehydrogenase subunits 2 (ND2) and 6 (ND6), and mutS homolog (msh1), 1633 bp] from 28 shallow-water species were sequenced to develop the first molecular phylogeny for Caribbean octocorals. The specimens were collected primarily in the Caribbean or off Brazil in 1999-2001. Morphological characters (sclerites and axial ultrastructure) were also examined in order to map them onto the molecular phylogeny. Analyses of both nucleotide and amino acid substitutions using maximum parsimony and likelihood (including maximum-likelihood and Bayesian analysis) generated very similar results, with most nodes having high levels of support. These molecular results were significantly different from the generally accepted classification. Neither Plexauridae nor Gorgoniidae were monophyletic. Plexaurella spp., nominal plexaurids, were basal to the gorgoniids, sharing many morphological characters with them. This corroborates previous findings using secondary metabolites and biosynthetic pathways. The sea fans, Gorgonia spp. and Pacifigorgia spp., as well as the pinnate gorgonians, Muriceopsis flavida and Pseudopterogorgia spp., did not have sea fan or pinnate relatives, suggesting there has been convergent evolution of colony form. Caribbean plexaurids appeared more derived and/or recently evolved according to both morphological and molecular data (e.g. Eunicea spp. and Plexaura spp.). Molecular phylogenetics is a promising approach for reconstructing phylogenetic relationships among octocorals as well as to understand their complex morphology.

Maturing amphibian oocytes undergo drastic morphological changes, including germinal vesicle breakdown (GVBD), chromosome condensation, and spindle formation in response to progesterone. Two kinases, maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK), are involved in these changes, but their precise roles are unknown. Unlike in Xenopus oocytes, discrimination of the functions of MAPK and MPF in Rana oocytes is easy owing to the lack of pre-MPF. We investigated the roles of these kinases by careful observations of chromosomes and microtubules in Rana oocytes. MPF and MAPK activities were manipulated by treatment with progesterone, c-mos mRNA, or cyclin B mRNA in combination with MAPK kinase inhibitors. Activation of one kinase without activation of the other induced only limited events; GVBD was induced by MPF without MAPK, and reorganization of microtubules at GVBD was induced by MAPK without MPF, but other events were not induced. In contrast, coactivation of MPF and MAPK by injection of c-mos and cyclin B mRNA promoted almost all of the morphological changes that occur during maturation without progesterone, indicating that these are controlled by cooperation of MPF and MAPK. The results revealed the functions of MAPK and MPF in each process of sequential morphological changes during oocyte maturation. Key Words: cyclin B; microtubules; chromosome condensation; spindle formation; Rana oocytes.

Teleost fin ray bifurcations are characteristic of each ray in each fin of the fishes. Control of the positioning of such morphological markers is not well understood. We present evidence suggesting that the interray blastema is necessary for a proper bifurcation of each ray during regeneration in Danio rerio (Hamilton-Buchanan) (Cyprinidae, Teleostei). We performed single ray ablations, heterotopical graftings of ray fragments and small holes in lateral rays which do not normally bifurcate, to generate recombinants in which the lateral rays are surrounded with ectopic interrays originating from different positions within the tail fin. These ray-interray recombinants do now bifurcate. Furthermore, we show that the interray tissue and surrounding epidermis can modulate the length of the ray. These results stress the role of the interray in inducing bifurcations of the ray blastema as well as modulating ray morphogenesis in general. In addition, gene expression analysis under these experimental conditions suggests that msxA and msxD expression in the ray and interray epidermis is controlled by the ray blastema and that bmp4 could be a candidate signal involved in these inductions. Key Words: Danio rerio; fin regeneration; epidermis-blastema interactions; msxA; msxD; bmp4; graftings; ray-interray interactions; ray bifurcation.

Results show that gene huckebein encoded protein HKB regulates polarized cell shape changes and apical membrane growth during epithelial tube morphogenesis. Furthermore in invaginating salivary cells, two genes mediate growth and delivery of apical membrane, which have bearing on the size and shape of the salivary tube.

Temporal shifts in the expression of regulatory genes, relative to other events taking place during development, can result in changes in morphology. Such transcriptional heterochrony can introduce dramatic morphological changes that involve rather few genetic events and so has the potential to cause rapid changes during evolution. We have shown previously that stereotyped species-specific bristle patterns on the notum of higher Diptera correlate with changes in the spatial regulation of scute expression, scute encodes a proneural gene required for the development of sensory bristle precursors and is expressed before pupation in discrete domains on the presumptive notum at sites where the macrochaete precursors arise. Thus, for Ceratitis capitata and Calliphora vicina, species separated from Drosophila melanogaster by about 80 and 100 million years respectively, the domains of sc expression differ. In all three species, a second phase of ubiquitous sc expression, after pupation, precedes formation of the microchaete precursors. Here, we describe sc expression in Phormia terranovae, a species belonging to the family Calliphoridae that is closely related to C. vicina. We find that spatial regulation is almost identical between P. terranovae and C. vicina, in spite of their different bristle patterns. The timing of sc expression differs, however, between the two. The first spatially restricted phase of expression is slightly delayed and the second ubiquitous phase remarkably accelerated, such that there is a period of overlap. As a result, the last precursors from the first phase of expression arise at the same time as the first precursors from the second phase of expression and are morphologically indistinguishable from the late-arising microchaetes. These observations illustrate the power of developmental heterochrony in bringing about rapid morphological change. Key Words: achaete-scute; bristle pattern; diptera; blowfly; heterochrony.

Selection is widely accepted as the principal force shaping phenotypic variation within populations. Its importance in speciation and macroevolution has been questioned, however, because phenotypic differences between species or higher taxa sometimes appear to be nonadaptive. Here, we use the quantitative trait locus (QTL) sign test to evaluate the importance of directional selection in phenotypic divergence. If a trait has a history of directional selection, QTL effects should be mostly in the same direction; otherwise QTLs with antagonistic effects should be common. Analysis of QTL effects for 572 traits from 86 studies revealed significantly fewer antagonistic QTLs than expected under neutrality, a result that validates Darwin's claim that phenotypic diversification is caused mainly by selection. Moreover, interspecific trait differences were more strongly or consistently selected than intraspecific differences, strengthening a growing consensus among students of speciation that directional selection is the primary cause of speciation. Contrary to studies of selection in contemporary populations, life history traits appear to be selected more strongly than morphological traits, but traits related to the timing of development are weakly selected relative to most other traits.

Research demonstrates that the Hox protein Deformed facilitates separation between the maxillary and mandibular head lobes through the activation of apoptosis genes, reaper and Abdominal-B, in the early Drosophila developmental stages, which sculpts segments into distinct shapes.

The authors review the publications on gynostemium. The topics of interest include the adnation and zygomorphy evolution, phylogenic distribution of gynostemium and labellum in lilioid monocots and dynamic evolutionary transitions in floral morphology.

Body length in C. elegans is regulated by a member of the TGF[beta] family, DBL-1. Loss-of-function mutations in dbl-1, or in genes encoding components of the signaling pathway it activates, cause worms to be shorter than wild type and slightly thinner (Sma). Overexpression of dbl-1 confers the Lon phenotype characterized by an increase in body length. We show here that loss-of-function mutations in dbl-1 and lon-1, respectively, cause a decrease or increase in the ploidy of nuclei in the hypodermal syncytial cell, hyp7. To learn more about the regulation of body length in C. elegans we carried out a genetic screen for new mutations causing a Lon phenotype. We report here the cloning and characterization of lon-3, lon-3 is shown to encode a putative cuticle collagen that is expressed in hypodermal cells. We show that, whereas putative null mutations in lon-3 (or reduction of lon-3 activity by RNAi) causes a Lon phenotype, increasing lon-3 gene copy number causes a marked reduction in body length. Morphometric analyses indicate that the lon-3 loss-of-function phenotype resembles that caused by overexpression of dbl-1. Furthermore, phenotypes caused by defects in dbl-1 or lon-3 expression are in both cases suppressed by a null mutation in sqt-1, a second cuticle collagen gene. However, whereas loss of dbl-1 activity causes a reduction in hypodermal endoreduplication, the reduction in body length associated with overexpression of lon-3 occurs in the absence of defects in hypodermal ploidy.

Research has been conducted on the miniaturization. The relationship between the body size miniaturization and morphology has been investigated via the comparison of the miniature frog population skeletons to those of related larger species and the results indicate that certain lineages are resistant to the morphological trends.

Research has been conducted on Drosophila simulans mitochondrial DNA population subdivision. Results suggest that mitochondrial DNA is not a good indicator of D. simulans organismal subdivision.

Research demonstrates that the degree of cotyledon asymmetry is not related to genome attributes in terms of heterozygosity, genomic co-adaptation, and genetic stress. Results do not support the effect of genetic crossing distance on the level of cotyledon developmental stability in Brassica cretica.

Research has been conducted on the sexual selection by scramble competition. The effect of gravity on the sexual size dimorphism evolution in spiders has been investigated and the results indicate that the gravity imposed constraint on climbing males is a selective factor in male dwarfism determination.

Research has been conducted on the escalation level and extinction selectivity of bivalves. The bivalves' metabolic rate has been tested via the use of oxygen isotope ratios of fossil bivalve shells and the results suggest that isotopic approach to metabolism determination may not support the extinction selectivity hypothesis.

NEDD8/Rub1 is a ubiquitin (Ub)-like molecule that covalently ligates to target proteins through an enzymatic cascade analogous to ubiquitylation. This modifier is known to target all cullin (Cul) family proteins. The latter are essential components of Skp1/Cul-1/F-box protein (SCF)--like Ub ligase complexes, which play critical roles in Ub-mediated proteolysis. To determine the role of the NEDD8 system in mammals, we generated mice deficient in Uba3 gene that encodes a catalytic subunit of NEDD8-activating enzyme. Uba[3.sup.-/-] mice died in utero at the periimplantation stage. Mutant embryos showed selective apoptosis of the inner cell mass but not of trophoblastic cells. However, the mutant trophoblastic cells could not enter the S phase of the endoreduplication cycle. This cell cycle arrest was accompanied with aberrant expression of cyclin E and p5[7.sup.Kip2]. These results suggested that the NEDD8 system is essential for both mitotic and the endoreduplicative cell cycle progression. [beta]-Catenin, a mediator of the Wnt/ wingless signaling pathway, which degrades continuously in the cytoplasm through SCF Ub ligase, was also accumulated in the Uba[3.sup.-/-] cytoplasm and nucleus. Thus, the NEDD8 system is essential for the regulation of protein degradation pathways involved in cell cycle progression and morphogenesis, possibly through the function of the Cul family proteins.

Research has been conducted on the filamentous bacterium Streptomyces coelicolor. Results indicate that the isolated mutant unable to produce an aerial mycelium demonstrates the delayed production of the blue-pigmented antibiotic actinorhodin.

Misidentified paternity and maternal effects have been studied relative to heritability of morphological traits in Darwin's Finches. To find parentage, data from eight microsatellite loci were used. Grandparent-offspring regressions evidence maternal effects, comparable in size to those seen in other wild bird studies.

Research describes six morphogenetic genes in Yarrowia lipolytica involved in hyphal formation and its filamentous morphology. Results show that a Ras-cyclic AMP pathway forms the hyphae and processing abnormalities of the extracellular and the parietal proteins lead to morphogenetic defects.

Research has been conducted on plasticity evolution. The fitness costs and phenotypic plasticity evolution have been investigated and the results are described.

Genetic variation of morphological traits in Drosophila melanogaster was studied. Heritabilities and genetic and phenotypic variances were in general higher in an isofemale line design than in a offspring-parent regression design with both standard and substandard nutrition. Wing length showed lower heritability under poor nutrition. Heritabilities of sternopleural bristle number and thorax length, however, did not differ in the two regimes.

Research has been conducted on the morphological variance-covariance structure evolution among house finch populations. Results indicate that the among-population morphological divergence in both males and females do not follow the within-population covariance patterns.

The evolution of gene regulation and morphological diversity is discussed in this minireview. Mounting evidence indicating a central role for differences in developmental gene regulation in intraspecific variation and body plans and body parts diversification is reviewed with changes in the cis-regulatory systems of genes and why changes in them more often are behind the evolution of morphological diversity than are changes in protein function or gene number. The sufficiency of evolutionary mechanisms seen below or at the species level to account for the larger scale patterns of morphological evolution is discussed from the developmental genetic perspective.

Evolutionary implications in the relationship between body size and genome size in copepods and flatworms have been studied. Genome and body sizes were measured in 38 turbellarian flatworm species and 16 copepod crustaceans species. Significant positive relations were seen between genome size and body size in both. Increases in cell volume are reinforced by greater cell numbers, or cell volumes show positive allometric variation with genome size. Genome sizes seem to vary discontinuously among congeneric species in both so such changes would have come on rapidly with potentially profound effects on important morphology.

Small numbers of important genes can govern extreme differences in morphology and may influence the rate of evolution of new adaptions in natural populations. A new study of Crepis tectorum ssp. pumila uses the factorial mating design to investigate the genetic variation in leaf morphology in a population that appears to have a dominant gene causing deep lobed leaves. Details of the study are presented.

Research demonstrates the key role of the environment in biological morphology, using lizard genera Anolis and Sceloporus as examples. Topics include a comparison of morphological traits, such as limb proportions and tail length, and of geographic location, such as tropic and arid, for both species.

Two important race groups of the stem nematode, Ditylenchus dipsaci, an obligatory polyphagous endoparasite, attack the bean, Vicia faba. Morphological differences have been found in the two groups and there were corresponding differences in faba bean disease symptoms. Agreement has been found between RAPD and phenotypic characteristics in the nematodes. Variation between D. dipsaci species in populations involved with V. faba was low. No strong correlation was found between geographical origin and morphological or molecular characteristics.

Nuclear restriction fragment length polymorphism (RFLP) diversity in Eucalyptus nitens has been investigated using 40 antonymous RFLP loci. Information on the probes came from the genetic linkage map of the species. The diversity in the nuclear genome was high compared with other species for which RFLP surveys have been done. Population similarities based on RFLP analysis of the nuclear genome did not agree with those based on the chloroplast genome.

The characterization of species as separate entities depends on some form of distinctiveness measured in genetic and/or phenotypic terms. The biological species concept and the geographic theories of speciation (Mayr [...]

SSF1 and SSF2 are redundant essential yeast genes that, when overexpressed, increase the mating efficiency of cells containing a defective Ste4p [G.sub.[Beta]] subunit. To identify the precise function of these genes in mating, different responses to pheromone were assayed in cells that either lacked or overexpressed SSF gene products. Cells containing null alleles of both SSF1 and SSF2 displayed the normal transcriptional induction response to pheromone but were unable to form mating projections. Overexpression of SSF1 conferred the ability to form mating projections on cells containing a temperature-sensitive STE4 allele, but had only a small effect on transcriptional induction. SSF1 overexpression preferentially increased the mating efficiency of a strain containing a null allele of SPA2, a gene that functions specifically in cell morphology. To investigate whether Ssf1p plays a direct physical role in mating projection formation, its subcellular location was determined. An Ssf1p-GFP fusion was found to localize to the nucleolus, implying that the role of SSF gene products in projection formation is indirect. The region of Ssf1p-GFP localization in cells undergoing projection formation was larger and more diffuse, and was often present in a specific orientation with respect to the projection. Although the function of Ssf1p appears to originate in the nucleus, it is likely that it ultimately acts on one or more of the proteins that is directly involved in the morphological response to pheromone. Because many of the proteins required for projection formation during mating are also required for bud formation during vegetative growth, regulation of the activity or amount of one or more of these proteins by Ssf1p could explain its role in both mating and dividing cells.

The yeast Zip1 protein (Zip1p) is a component of the central region of the synaptonemal complex (sc). Zip1p is predicted to form a dimer consisting of a coiled-coil domain flanked by globular domains. To analyze the organization of Zip1p within the SC, in-frame deletions of ZIP1 were constructed and analyzed. The results demonstrate that the C terminus but not the N terminus of Zip1p is required for its localization to chromosomes. Deletions in the carboxy half of the predicted coiled-coil region cause decreases in the width of the SC. based on these results, a model for the organization of Zip1p within the SC is proposed. zip1 deletion mutations were also examined for their effects on sporulation, spore viability, crossing over, and crossover interference. The results demonstrate that the extent of synapsis is positively correlated with the levels of spore viability, crossing over, and crossover interference. In contrast, the role of Zip1p in synapsis is separable from its role in meiotic cell cycle progression. zip1 mutants display interval-specific effects on crossing over.

The specification of floral organ identity in the higher dicots depends on the function of a limited set of homeotic genes, many of them members of the MADS-box gene family. Two such genes, APETALA3 (AP3) and PISTILLATA (PI), are required for petal and stamen identity in Arabidopsis; their orthologs in Antirrhinum exhibit similar functions. To understand how changes in these genes may have influenced the morphological evolution of petals and stamens, we have cloned twenty-six homologs of the AP3 and PI genes from two higher eudicot and eleven lower eudicot and magnolid dicot species. The sequences of these genes reveal the presence of characteristic PI- and AP3-specific motifs. While the PI-specific motif is found in all of the PI genes characterized to date, the lower eudicot and magnolid dicot AP3 homologs contain distinctly different motifs from those seen in the higher eudicots. An analysis of all the available AP3 and PI sequences uncovers multiple duplication events within each of the two gene lineages. A major duplication event in the AP3 lineage coincides with the base of the higher eudicot radiation and may reflect the evolution of a petal-specific AP3 function in the higher eudicot lineage.

A new mutant of Arabidopsis thaliana that initiates flowering early and terminates the inflorescence with floral structures has been identified and named terminal flower2 (tfl2). While these phenotypes are similar to that of the terminal flower1 (tfl1) mutant, tfl2 mutant plants are also dwarfed in appearance, have reduced photoperiod sensitivity and have a more variable terminal flower structure. Under long-day and short-day growth conditions till tfl2 double mutants terminate the inflorescence without development of lateral flowers; thus, unlike tfl1 single mutants the double mutant inflorescence morphology is not affected by day length. The enhanced phenotype of the double mutant suggests that TFL2 acts in a developmental pathway distinct from TFL1. The complex nature of the tfl2 single mutant phenotype suggests that TFL2 has a regulatory role more global than that of TFL1. Double mutant analysis of tfl2 in combination with mutant alleles of the floral meristem identity genes LEAFY and APETALA1 demonstrates that TFL2 function influences developmental processes controlled by APETALA1, but not those regulated by LEAFY. Thus, the TFL2 gene product appears to have a dual role in regulating meristem activity, one being to regulate the meristem response to light signals affecting the development of the plant and the other being the maintenance of inflorescence meristem identity.

Postgenital organ fusion occurs most commonly during reproductive development and is important in many angiosperms during genesis of the carpel. Although a number of mutants have been described that manifest ectopic organ fusion, little is known about the genes involved in regulating this process. In this article we describe the characterization of a collection of 29 Arabidopsis mutants showing an organ fusion phenotype. Mapping and complementation analyses revealed that the mutant alleles define nine different loci distributed throughout the Arabidopsis genome. Multiple alleles were isolated for the four complementation groups showing the strongest organ fusion phenotype while the remaining five complementation groups, all of which show only weak floral organ fusion, have a single representative allele. In addition to fusion events between aerial parts of the shoot, some mutants also show abnormal ovule morphology with adjacent ovules.joined together at maturity. Many of the fusion mutants isolated have detectable differences in the rate at which chlorophyll can be extracted; however, in one case no difference could be detected between mutant and wild-type plants. In three mutant lines pollen remained unresponsive to contact with the mutant epidermis, demonstrating that organ fusion and pollen growth responses can be genetically separated from one another.

The analysis of possible effects of B chromosomes in Locusta migratoria, migratory locusts, in Spain, on several physiological and morphological traits and some other traits that pertain to female fitness is discussed. No harmful effects of a selfish B chromosome are seen on several morphological and physiological traits, and B chromosomes were not seen to be strongly parasitic in the studied population.

Insights derived from morphological and allozyme markers as they relate to genetic-variation/gene-flow in polyploid populations of Lotus (L. alpinus (D.C.) Schleicher/L. corniculatus L.) in the Alps are discussed. The diploid cytotype L. alpinus may be the ancestor of the alpine tetraploids, but gene flow between cytotypes seems to be limited and genetic introgression would seem to occur between the two tetraploid species.

Two closely related species of Drosophila, D. simulans and D. mauritiana, differ markedly in morphology of the posterior lobe of the male genital arch. Both size and shape aspects of lobe variation can be quantified by a morphometric descriptor based on elliptical Fourier and principal components analyses. The genetic architecture of this quantitative trait (PC1) was investigated by hybridizing inbred lines to produce two backcross populations of [approximately]200 individuals each, which were analyzed jointly by a composite interval mapping procedure with the aid of 18 marker loci. The parental lines show a large difference in PC1 (30.4 environmental standard deviations), and the markers account for >80% of the phenotypic variation in backcross populations. Eight of 15 intervals analyzed show convincing evidence of quantitative trait loci (QTL), and the range of estimated QTL effects is 5.7-15.9% of the parental difference (1.7-4.8 environmental standard deviations). These estimates may represent the joint effects of multiple QTL within a single interval (which averaged 23 cM in length). Although there is some evidence of partial dominance of mauritiana alleles and for epistasis, the pattern of inheritance is largely additive.

1 Studies of morphological plasticity in clonal plants have analysed responses to habitat quality in terms of spacer (stolon or rhizome internode) length and branching intensity. The capacity for these parameters to respond to environmental quality has been interpreted as an expression of foraging behaviour, as it confers the potential to intensify the placement of ramets in the more favourable microhabitats (patches) of a heterogeneous environment. This plasticity in clonal morphology is compared with similar responses of individual shoots and roots to habitat quality that have also been accepted as manifestations of foraging behaviour. 2 The most consistent morphological response shown by clonal species is a higher branching intensity - an increased propensity of lateral meristems to grow out and form lateral rhizomes and stolons - under conditions of higher resource supply. In contrast, spacer lengths show a variety of responses to light and nutrient availability, and many species exhibit no significant response. Even in stoloniferous species, where stolon internodes tend to shorten under higher photon flux densities, the degree of shortening may often be insufficient to elicit a significant concentration of ramets in favourable habitat patches. 3 Many clonal and nonclonal species have however, been shown to be very efficient in placing leaves and roots in areas of high resource supply within their environment. This is achieved by a high level of morphological plasticity of the shoot and root branches. 4 We therefore suggest that it is the highly plastic changes in the morphology of individual ramets that enable effective exploitation of local concentrations of essential resources once they have been located. The unresponsive spacer lengths of many clonal species may permit a continuous search of habitat space by the plant, rather than a selective placement of ramets. 5 The foraging concept is reformulated in more general terms relating to resource-acquisition strategies, so that it is applicable to both clonal and nonclonal species of plants. Keywords: clonal branching, habitat heterogeneity, internode length, resource acquisition, simulation studies

Migration by flight is an important component of the life cycles of most insects. The probability that a given insect will migrate by flight is influenced by many factors, most notably the presence or absence of fully-developed wings and functional flight musculature. Considerable variation has also been reported in the flight propensity of full-winged individuals with functional flight musculature. We test the hypothesis that these components of migratory tendency are genetically correlated in a wing-dimorhic cricket, Gryllus firmus. Flight propensity and condition of the dorsal longitudinal flight muscles (DLM) are examined in fully-winged (LW) crickets from lines selected for increasing and for decreasing %LW, as well as from unselected control lines. Increased %LW is found to be associated with increased flight propensity among individuals with intact DLM, and with retention of functional DLM. The opposite is true for lines selected for decreased %LW. These results indicate both phenotypic and genetic correlations among behavioral, physiological, and morphological traits determining migratory tendency. We propose that these correlations may result from the multifunctional role of juvenile hormone, which has been reported to influence wing development, flight muscle development and degeneration, and flight propensity. Finally, discuss the potential influence of genetic correlations for migratory traits on the evolution and maintenance of migratory polymorphisms in insects.

This paper discusses the use of duplicated structures in evolution. Duplication, followed by variation and modification of function, has been a major strategy from the time of the early biological molecules to the evolution of advanced morphological complexity. Evolution by duplication with variation produces a hierarchically structured organizational logic based on nested segments, or metameres. The genome is itself largely structured in this way by the process of gene duplication. Duplicate genes often maintain related function and even chromosomal arrangement, and the expression of those related genes may be coordinated, often by regulatory genes, which are themselves the products of gene duplication. The morphology of complex metazoan organisms has evolved in a metameric way from early in evolution, by the use of repeat units in histology and repeated morphological segments. Recent advances in genetics have shown that there is a direct correspondence between these morphological structures and metameric structures in the genome, suggesting how complex morphology was produced by evolution at the gene level. Examples from invertebrates and vertebrates show that homologous processes are involved in morphogenesis in both groups, with strictly homologous processes are involved in morphogenesis in both groups, with strictly homologous developmental genes retaining very similar function and regulation. These issues are highly relevant to an improved understanding of macroevolution and to the core questions of biological anthropology. The evolution of dental morphology is discussed as an example.

In the Gram-positive bacteria, cell shape is determined by the MreB family of proteins that form helical, actin-like cables in the cell and occurs by diverse molecular pathways. Research reveals that in the rod-shaped Bacillus subtilis synthesis of the cell wall cylindrical structure occurs in a helical pattern, mediated by an MreB homolog. However, in a few rod-like bacteria the rod shape is accomplished by polar growth zones.

Research has been conducted on Hyla nana and Hyla sanborni specimens. The authors have investigated these specimens cytogenetically, and they report that chromosomal morphology of these species is different from that of the populations from other georgaphic regions.

Research has been conducted on morphological traits in Lipizzan horses. The authors have measured morphological traits in Lipizzan mares and regressed them on the individual inbreeding coefficients and on the heterozygosity and mean square distances between microsatellite alleles within an individual, and they report that inbreeding, microsatellite heterozygosity and mean square distances between microsatellite alleles have no large effects on Lipizzan horses' morphological traits.

Research has been conducted on mice selected for high voluntary wheel-running activity. The authors have studied the role of genetic drift, early-age selection and activity environment in the shape and position of food consuming, wheel-running and body-mass ontogenies.

Research has been conducted on sand cricket Gryllus firmus inbreeding, developmental stability and canalization. The association between variation in canalization and developmental stability's fluctuating asymmetry has been investigated, and the results are reported.