Isolation and characterization of thermophilic bacteria from natural and artificial habitats

Several thermophilic Bacillus Strains were isolated from natural as well as artificial habitats. They grow optimally on a carbohydrate-containing medium at a temperature of 65 to 68°C and a pH value of 6 to 7 under aerobic conditions. They utilize glucose, sucrose and sodium acetate as carbon and energy sources. They can be differentiated by acid formation and composition of intracellular fatty acid fraction as well as growth on xylose, lactose, starch, cellobiose, ribose and galactose.     

Patterns of sexual dimorphism from birth to senescence

Sexual dimorphism is expressed as median of the female values in percent of the median of the male values, of 4 length measurements, 3 circumferences, and 5 measurements of corpulence respectively fat. Data were obtained from a cross-sectional sample of more than 41.000 German subjects, aged from birth to age 62. The pattern of sexual dimorphism is similar in the length measurements. Girls are shorter at birth, but they increase in length at higher rates than boys and even temporarily overgrow the boys up to age 12. Thereafter, males show an obvious growth advantage leading to some 6 to 9% more length in adult males. In contrast, female circumferences are always smaller, from birth to senescence. Though, the differences between the sexes are low in circumferences, up to age 13, sexual dimorphism increases to 17% in the thoracic circumference at adulthood. Sexual dimorphism in weight and BMI is comparably with that in length measurements while subcutaneous fat and total body fat content are always higher in females. The results highlight that sexual dimorphism develops at different pace in the various components of the body and that it associates with a sex specific growth tempo.     

Genetic constraints and the evolution of display trait sexual dimorphism by natural and sexual selection

The evolution of sexual dimorphism involves an interaction between sex-specific selection and a breakdown of genetic constraints that arise because the two sexes share a genome. We examined genetic constraints and the effect of sex-specific selection on a suite of sexually dimorphic display traits in Drosophila serrata. Sexual dimorphism varied among nine natural populations covering a substantial portion of the species range. Quantitative genetic analyses showed that intersexual genetic correlations were high because of autosomal genetic variance but that the inclusion of X-linked effects reduced genetic correlations substantially, indicating that sex linkage may be an important mechanism by which intersexual genetic constraints are reduced in this species. We then explored the potential for both natural and sexual selection to influence these traits, using a 12-generation laboratory experiment in which we altered the opportunities for each process as flies adapted to a novel environment. Sexual dimorphism evolved, with natural selection reducing sexual dimorphism, whereas sexual selection tended to increase it overall. To this extent, our results are consistent with the hypothesis that sexual selection favors evolutionary divergence of the sexes. However, sex-specific responses to natural and sexual selection contrasted with the classic model because sexual selection affected females rather than males.     

Insights into the ecology of Schizosaccharomyces species in natural and artificial habitats

The fission yeast genus Schizosaccharomyces contains important model organisms for biological research. In particular, S. pombe is a widely used model eukaryote. So far little is known about the natural and artificial habitats of species in this genus. Finding out where S. pombe and other fission yeast species occur and how they live in their habitats can promote better understanding of their biology. Here we investigate in which substrates S. pombe, S. octosporus, S. osmophilus and S. japonicus are present. To this end about 2100 samples consisting of soil, tree sap fluxes, fresh fruit, dried fruit, honey, cacao beans, molasses and other substrates were analyzed. Effective isolation methods that allow efficient isolation of the above mentioned species were developed. Based on the frequency of isolating different fission yeast species in various substrates and on extensive literature survey, conclusions are drawn on their ecology. The results suggest that the primary habitat of S. pombe and S. octosporus is honeybee honey. Both species were also frequently detected on certain dried fruit like raisins, mango or pineapple to which they could be brought by the honey bees during ripening or during drying. While S. pombe was regularly isolated from grape mash and from fermented raw cacao beans S. octosporus was never isolated from fresh fruit. The main habitat of S. osmophilus seems to be solitary bee beebread. It was rarely isolated from raisins. S. japonicus was mainly found in forest substrates although it occurs on fruit and in fruit fermentations, too.

     

Differences in trait compositions between rocky natural and artificial habitats

Question: What are the differences in trait compositions that enable native plants to colonise comparable natural and man‐made habitats? Are these traits independent of phylogenetic relationships between species? Location: Czech Republic. Methods: The relative importance of biological, ecological and distributional traits of native species was studied, using a dataset of 75 species growing in rock and wall habitats in the Czech Republic. Species preferences for individual habitats due to climatic conditions and proportions of different vegetation types in their surroundings were partialled out using partial canonical correspondence analysis. The pattern of plant traits along a gradient from natural rock habitats to secondary wall habitats was analysed using regression trees and generalized linear models with and without phylogenetic correction. Results: The most common native species colonising rock habitats are phanerophytes, mostly woody juveniles, with a CSR life strategy and most are adapted to epizoochory. Summer green leaves, annual life span, CR life strategy, reproduction mostly by seeds and dispersal by ants are all traits positively associated with the ability of species to colonise wall habitats. These species are also characterised by their high demand for nutrients, temperature, base‐rich substrates and light. Biological and ecological traits are more important for colonising new habitats than traits related to species dispersal ability or phylogenetic relationships between species. Biological and ecological traits alone explained 29.3% of variability in the species dataset, while dispersal characteristics and phylogeny alone explained 9.1% and 4.8%, respectively. Conclusions: We outline how the process of environmental filtering determines native species assemblages and identify a set of species traits that enable them to persist in particular habitats. We conclude that although urbanisation generally results in loss of natural habitats, there are new, man‐made habitats potentially suitable for native species.     

Ontogenetic approaches to sexual dimorphism in anthropoids

Studies of sexual dimorphism have traditionally focused on the static differences in size and shape between adult males and females. In this paper, I suggest that an investigation of the ontogenetic bases of sexual dimorphism can provide new insights and information unobtainable from studies concerned only with adult endpoints. While growth is often viewed as simply the developmental pathway utilized to attain final adult size and shape, we must recognize that it is the entire pattern of sex-differentiated growth, and not merely the adult endpoints, which is adaptive and the target of natural selection. The importance of an ontogenetic approach to the analysis of sexual dimorphism is also demonstrated by the fact that a given morphologicalresult (e.g., a certain degree of adult weight dimorphism) may be attained by very different developmentalprocesses, signalling selection for quite different factors. The need to analyze the ontogenetic bases of sexual dimorphism in size and shape has recently been recognized by Jarman, in his study of dimorphism in large terrestrial herbivores. Here I combine aspects of Jarman’s approach with those of allometry and heterochrony in an analysis of sexual dimorphism in selected anthropoid primates. It is demonstrated that although all dimorphic anthropoids appear to be characterized by somebimaturism, the degree varies significantly. Marked weight dimorphism in certain species is primarily produced by an increased differentiation of female and male growthrates, while in other species the primary change involves differences in thetime or duration of growth between the sexes. These variations are illustrated with anthropoid genera such asMiopithecus, Cercopithecus, Erythrocebus, Macaca, Papio, Pan, andGorilla. It is suggested that additional ontogenetic investigations of other anthropoids will help clarify some of the socioecological bases of this variation in the ways of attaining an adult dimorphic state. This will contribute to our understanding of the complex factors underlying and producing sexual dimorphism in primates and other mammals.     

Inferring social behavior from sexual dimorphism in the fossil record

Sexual dimorphism is commonly used as evidence of the behavior of extinct species. Even so, few analyses scrutinize whether extant comparative data support inferences of mating systems or behavior in extinct species. This analysis evaluates the relations between measures of dimorphism and several estimates of mating system and intrasexual competition. Dimorphism alone provides poor resolution for reconstructing behavior. Many behavioral inferences based on perceived dimorphism are not supported by extant comparative data. This reflects the large standard errors of relations between dimorphism estimates and behavioral classifications. Used with caution, dimorphism can provide a hint of the behavior of extinct species in some cases. However, in many cases inferred dimorphism allows little more than an inference of polygyny, without any indication of specific types of mating systems.     

Visualizing sexual dimorphism in the brain

Sexually dimorphic behaviors are likely to involve neural pathways that express the androgen receptor (AR). We have genetically modified the AR locus to visualize dimorphisms in neuronal populations that express AR. Analysis of AR-positive neurons reveals both known dimorphisms in the preoptic area of the hypothalamus and the bed nucleus of the stria terminalis as well as novel dimorphic islands in the basal forebrain with a clarity unencumbered by the vast population of AR-negative neurons. This genetic approach allows the visualization of dimorphic subpopulations of AR-positive neurons along with their projections and may ultimately permit an association between neural circuits and specific dimorphic behaviors.     

Direct and correlated responses to artificial selection on sexual size dimorphism in the flour beetle, Tribolium castaneum

Sexual size dimorphism (SSD) is a conspicuous yet poorly understood pattern across many organisms. Although artificial selection is an important tool for studying the evolution of SSD, previous studies have applied selection to only a single sex or to both sexes in the same direction. In nature, however, SSD likely arises through sex-specific selection on body size. Here, we use Tribolium castaneum flour beetles to investigate the evolution of SSD by subjecting males and females to sexually antagonistic selection on body size (sexes selected in opposite directions). Additionally, we examined correlated responses to body size selection in larval growth rates and development time. After seven generations, SSD remained unchanged in all selected lines; this observed lack of response to short-term selection may be attributed to evolutionary constraints arising from between-sex body size correlations. Developmental traits showed complex correlated responses under different selection treatments. These results suggest that sex-specific larval development patterns may facilitate the evolution of SSD.     

Sexual dimorphism in human skulls. A comparison of sexual dimorphism in different populations

Application and comparison of sex discriminant functions in different populations led to the conclusion that a certain combination and weighting of a few sex dimorphism variables (in this study we only used craniometric variables) can give a good discrimination between male and female individuals, independent of the racial group to which this function is applied. In our study, the sex-discriminatory power of five discriminant functions which were based on different ordination and selection procedures (e.g. professional knowledge, stepwise discriminant analysis, literature) of the cranial variables is compared. These discriminant functions were applied to three different data sets, the first being skull measurements from an Amsterdam series (Europids), the second skull measurements of a Zulu series (Negrids) and the third skull measurements of a Japan series (Mongolids). Our decision as to whether a function is a good or less good sex-discriminating function is determined by the Dt values (these values give an idea about the discriminatory value of the discriminant function when applied to a new test sample), the number of variables necessary to obtain this Dt and the location of the sectioning point (i.e. comparison between the estimation of the sectioning point and the ”real” sectioning point). These discriminant functions were compared withGiles Elliot's (1962, 1963) “race-independent” sex function.     

A geometric approach to cranial sexual dimorphism in the orang-utan

Adult craniofacial morphology is quantified and compared using Euclidean distance matrix analysis (EDMA), a three-dimensional morphometric method for the comparison of forms, which localizes form differences between comparative groups. Results indicate that the number and magnitude of differences between male and female crania are striking. The face, basicranium and neurocranium exhibit the most dimorphism, while the palate shows the least. Significant differences also exist between young adult and fully adult individuals, especially males, supporting the delayed onset of sexual maturity and secondary sex characteristics in males. As one of the many new morphometric techniques available, EDMA was useful for identifying local form difference and provides insights into the understanding of sexual dimorphism in this species beyond that obtained from traditional statistical methods based on linear caliper measurements.     

Evolution of sexual size dimorphism in birds: test of hypotheses using blue tits in contrasted Mediterranean habitats

Many hypotheses, either sex‐related or environment‐related, have been proposed to explain sexual size dimorphism in birds. Two populations of blue tits provide an interesting case study for testing these hypotheses because they live in contrasting environments in continental France and in Corsica and exhibit different degree of sexual size dimorphism. Contrary to several predictions, the insular population is less dimorphic than the continental one but neither the sexual selection hypothesis nor the niche variation hypothesis explain the observed patterns. In the mainland population it is advantageous for both sexes to be large, and males are larger than females. In Corsica, however, reproductive success was greater for pairs in which the male was relatively small, i.e. pairs in which sexual size dimorphism is reduced. The most likely explanation is that interpopulation differences in sexual size dimorphism are determined not by sex‐related factors, but by differences in sex‐specific reproductive roles and responses to environmental factors. Because of environmental stress on the island as a result of food shortage and high parasite infestations, the share of parents in caring for young favours small size in males so that a reduced sexual size dimorphism is not the target of selection but a by‐product of mechanisms that operate at the level of individual sexes.     

Killer-sensitive relationships in yeasts from natural habitats

Yeast strains (157) belonging to at least 9 genera were isolated from natural habitats and screened for killer-sensitive relationships. Killer and sensitive characteristics were exhibited by 17 and 11 percent of the isolates, respectively. The strains belong to either one of two mutually exclusive killer-sensitive groups.     

Disproportionate sexual dimorphism in the human face

Analysis of facial dimensions of 86 young adults and their 76 parents indicates that a disproportionate sexual dimorphism exists in the ramus of the mandible, demonstrating a regional difference in growth response. The male ramus is on the average 14% longer than the female ramus, whereas other facial dimensions approximate an 8% sex difference. The findings have relevance to the analysis of skeletal remains and suggest the desirability of age specific discriminant function analysis for the sexing of adult mandibles.     

Robusticity and sexual dimorphism in the postcranium of modern hunter-gatherers from Australia

Throughout much of prehistory, humans practiced a hunting and gathering subsistence strategy. Elevated postcranial robusticity and sexually dimorphic mobility patterns are presumed consequences of this strategy, in which males are attributed greater robusticity and mobility than females. Much of the basis for these trends originates from populations where skeletal correlates of activity patterns are known (e.g., cross-sectional geometric properties of long bones), but in which activity patterns are inferred using evidence such as archaeological records (e.g., Pleistocene Europe). Australian hunter-gatherers provide an opportunity to critically assess these ideas since ethnographic documentation of their activity patterns is available. We address the following questions: do skeletal indicators of Australian hunter-gatherers express elevated postcranial robusticity and sexually dimorphic mobility relative to populations from similar latitudes, and do ethnographic accounts support these findings. Using computed tomography, cross-sectional images were obtained from 149 skeletal elements including humeri, radii, ulnae, femora, and tibiae. Cross-sectional geometric properties were calculated from image data and standardized for body size. Australian hunter-gatherers often have reduced robusticity at femoral and humeral midshafts relative to forager (Khoi-San), agricultural/industrialized (Zulu), and industrialized (African American) groups. Australian hunter-gatherers display more sexual dimorphism in upper limb robusticity than lower limb robusticity. Attributing specific behavioral causes to upper limb sexual dimorphism is premature, although ethnographic accounts support sex-specific differences in tool use. Virtually absent sexual dimorphism in lower limb robusticity is consistent with ethnographic accounts of equivalently high mobility among females and males. Thus, elevated postcranial robusticity and sexually dimorphic mobility do not always characterize hunter-gatherers.     

Changes in the sexual dimorphism of the human mandible during the last 1200 years in Central Europe

According to many investigations, changes in mandibular morphology can occur synchronously with changes in the environment, and sexual dimorphism of the mandible can be influenced by the environment. Sexual dimorphism during the last 1200 years was evaluated using geometric morphometric analysis of virtual cranial models. The method of geometric morphometrics allows differences in size and shape to be assessed separately. We analyzed groups of adult individuals dating to Early Middle Ages, High Middle Ages, Early Modern Ages and from a modern Czech population (21st century). Significant sexual dimorphism in mandibular size was found in all populations. A trend in the sexual dimorphism of size was seen, with differences between the sexes increasing gradually over time. Size changes in female mandibles were a better reflection of environmental conditions and climate than size changes in male mandibles. Regarding changes in the sexual dimorphism of shape, significant dimorphism was found in all four samples. However, the pattern of mandibular shape dimorphism was different and varied considerably between samples. There was only one stable shape trait showing sexual dimorphism across all four samples in our study: the gonion lies more laterally in male than in female mandibles and male mandibles are relatively wider than female mandibles. Sexual dimorphism of shape is not influenced by the climate; instead sexual selection might play a role. This research supports earlier studies that have found that the degree and pattern of sexual dimorphism is population-specific and the factors regulating sexual dimorphism today may not be the same as those in the past.     

Human marriage systems and sexual dimorphism in stature.

Contemporary populations of Homo sapiens are sexually dimorphic on a variety of traits. In terms of stature, men are reliably between 4% and 10% taller than women in well-sampled human populations. Are cross-cultural differences in the magnitude of sexual dimorphism consistent with expectations from sexual selection theory? Prior studies have provided conflicting answers to this question in part because they failed to agree on how the force of sexual selection should or could be operationalized. Here we offer a simple and unbiased method for operationalizing sexual selection and retest two separate predictions from earlier work (Alexander et al., 1979) about its expected impact on stature dimorphism in a sample of 155 societies. Neither prediction matches the observed cross-cultural distribution of dimorphism. However, this is not the consequence of a random distribution of dimorphism across societies. Instead, the data exhibit a robust and unexpected pattern.     

On the origins of sexual dimorphism in butterflies

The processes governing the evolution of sexual dimorphism provided a foundation for sexual selection theory. Two alternative processes, originally proposed by Darwin and Wallace, differ primarily in the timing of events creating the dimorphism. In the process advocated by Darwin, a novel ornament arises in a single sex, with no temporal separation in the origin and sex-limitation of the novel trait. By contrast, Wallace proposed a process where novel ornaments appear simultaneously in both sexes, but are then converted into sex-limited expression by natural selection acting against showy coloration in one sex. Here, we investigate these alternative modes of sexual dimorphism evolution in a phylogenetic framework and demonstrate that both processes contribute to dimorphic wing patterns in the butterfly genera Bicyclus and Junonia. In some lineages, eyespots and bands arise in a single sex, whereas in other lineages they appear in both sexes but are then lost in one of the sexes. In addition, lineages displaying sexual dimorphism were more likely to become sexually monomorphic than they were to remain dimorphic. This derived monomorphism was either owing to a loss of the ornament ('drab monomorphism') or owing to a gain of the same ornament by the opposite sex ('mutual ornamentation'). Our results demonstrate the necessity of a plurality in theories explaining the evolution of sexual dimorphism within and across taxa. The origins and evolutionary fate of sexual dimorphism are probably influenced by underlying genetic architecture responsible for sex-limited expression and the degree of intralocus sexual conflict. Future comparative and developmental work on sexual dimorphism within and among taxa will provide a better understanding of the biases and constraints governing the evolution of animal sexual dimorphism.