BACKGROUND: The tendency for male-larger sexual size dimorphism (SSD) to scale with body size - a pattern termed Rensch's rule - has been empirically supported in many animal lineages. Nevertheless, its theoretical elucidation is a subject of debate. Here, we exploited the extreme morphological variability of domestic dog (Canis familiaris) to gain insights into evolutionary causes of this rule. METHODOLOGY/PRINCIPAL FINDINGS: We studied SSD and its allometry among 74 breeds ranging in height from less than 19 cm in Chihuahua to about 84 cm in Irish wolfhound. In total, the dataset included 6,221 individuals. We demonstrate that most dog breeds are male-larger, and SSD in large breeds is comparable to SSD of their wolf ancestor. Among breeds, SSD becomes smaller with decreasing body size. The smallest breeds are nearly monomorphic. CONCLUSIONS/SIGNIFICANCE: SSD among dog breeds follows the pattern consistent with Rensch's rule. The variability of body size and corresponding changes in SSD among breeds of a domestic animal shaped by artificial selection can help to better understand processes leading to emergence of Rensch's rule.
Sexual dimorphism is responsible for a substantial part of human facial variability, the study of which is essential for many scientific fields ranging from evolution to special biomedical topics. Our aim was to analyse the relationship between size variability and shape facial variability of sexual traits in the young adult Central European population and to construct average surface models of adult males and females. The method of geometric morphometrics allowed not only the identification of dimorphic traits, but also the evaluation of static allometry and the visualisation of sexual facial differences. Facial variability in the studied sample was characterised by a strong relationship between facial size and shape of sexual dimorphic traits. Large size of face was associated with facial elongation and vice versa. Regarding shape sexual dimorphic traits, a wide, vaulted and high forehead in combination with a narrow and gracile lower face were typical for females. Variability in shape dimorphic traits was smaller in females compared to males. For female classification, shape sexual dimorphic traits are more important, while for males the stronger association is with face size. Males generally had a closer inter-orbital distance and a deeper position of the eyes in relation to the facial plane, a larger and wider straight nose and nostrils, and more massive lower face. Using pseudo-colour maps to provide a detailed schematic representation of the geometrical differences between the sexes, we attempted to clarify the reasons underlying the development of such differences.
- MeSH
- Finite Element Analysis MeSH
- Models, Anatomic MeSH
- Forehead anatomy & histology MeSH
- Sex Characteristics MeSH
- Facies MeSH
- Humans MeSH
- Young Adult MeSH
- Nose anatomy & histology MeSH
- Eye anatomy & histology MeSH
- Imaging, Three-Dimensional MeSH
- Check Tag
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Comparative Study MeSH
- Geographicals
- Europe MeSH
The subject of study was the anthropometry of an adult population in the period of early adulthood. In this study we evaluated twenty-four anthropometric parameters of Slovak population from three different districts (Bardejov, Zvolen and Považská Bystrica) in Slovakia. Our dataset consisted of 200 probands (108 men and 92 women) of young productive peoples with the age 18 to 35 years old with mean age 22.45 years for men. We measured body mass (V1) and 24 anthropometric parameters (V2 - V24). It also included calculation of the body mass index (BMI). The measurements in sexes overlapped, but both the univariate analysis (unpaired t-test) and multivariate analysis (two-way ANOVA) confirmed significant differences between them. The results of BMI values confirmed that both sexes belongs to “about right” weight category, i.e. the values in the range (18.50-24.99 kg/m2). For males and females were confirmed positive allometry between body mass and body height. Our data confirmed men biased sexual dimorphism with significantly higher dimensions than women and these results are fully consistent with the previous findings from above cited authors. Different allometric patterns obtained for sexes suggests that different changes during growth exist and may be due by different role in reproduction.
- MeSH
- Anthropometry * methods MeSH
- Adult MeSH
- Epidemiologic Factors MeSH
- Body Mass Index MeSH
- Humans MeSH
- Young Adult MeSH
- Growth MeSH
- Statistics as Topic MeSH
- Body Weights and Measures * methods statistics & numerical data MeSH
- Age Factors MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Slovakia MeSH
Green algae of the genus Halimeda have modular siphonous thalli composed of multiple repeated segments. Morphological variation among the segments has been related to various environmental factors, which often jointly affect their size and shape. The segments are bilaterally symmetric, which means that their shape variation can be decomposed into the symmetric and asymmetric components. Asymmetric variation might reflect both environmental heterogeneity and developmental instability of morphogenetic processes during the development of segments. In the present study, we examined if segment shape in H. tuna is related to their size and if an allometric relationship can also be found with respect to their asymmetry. Relative contributions of directional and fluctuating asymmetry to the segment shape variation within individual plants were investigated at two close localities in the northern Adriatic Sea. A series of equidistant semilandmarks were set along the outline of the segments, and analyzed by geometric morphometrics using two parallel methods to optimize their final position. Symmetric variation was strongly constrained by allometry, which also explained differences between populations. Smaller segments were significantly more asymmetric, but the difference in asymmetry between populations could not be explained solely by this allometric relationship. These differences between populations might have been caused by variation in local environmental factors. We conclude that members of the genus Halimeda represent an intriguing model system for studies of morphometric symmetry and asymmetry of sessile marine organisms, including effects of allometric relationships and infraspecific variation in relation to environmental factors of the benthic coastal habitats.
- MeSH
- Biological Evolution MeSH
- Models, Biological MeSH
- Chlorophyta anatomy & histology physiology MeSH
- Ecosystem MeSH
- Morphogenesis physiology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
1. Predation is often size selective, but the role of other traits of the prey and predators in their interactions is little known. This hinders our understanding of the causal links between trophic interactions and the structure of animal communities. Better knowledge of trophic traits underlying predator-prey interactions is also needed to improve models attempting to predict food web structure and dynamics from known species traits. 2. We carried out laboratory experiments with common freshwater macroinvertebrate predators (diving beetles, dragonfly and damselfly larvae and water bugs) and their prey to assess how body size and traits related to foraging (microhabitat use, feeding mode and foraging mode) and to prey vulnerability (microhabitat use, activity and escape behaviour) affect predation strength. 3. The underlying predator-prey body mass allometry characterizing mean prey size and total predation pressure was modified by feeding mode of the predators (suctorial or chewing). Suctorial predators fed upon larger prey and had ˜3 times higher mass-specific predation rate than chewing predators of the same size and may thus have stronger effect on prey abundance. 4. Strength of individual trophic links, measured as mortality of the focal prey caused by the focal predator, was determined jointly by the predator and prey body mass and their foraging and vulnerability traits. In addition to the feeding mode, interactions between prey escape behaviour (slow or fast), prey activity (sedentary or active) and predator foraging mode (searching or ambush) strongly affected prey mortality. Searching predators was ineffective in capturing fast-escape prey in comparison with the remaining predator-prey combinations, while ambush predators caused higher mortality than searching predators and the difference was larger in active prey. 5. Our results imply that the inclusion of the commonly available qualitative data on foraging traits of predators and vulnerability traits of prey could substantially increase biological realism of food web descriptions.
- MeSH
- Invertebrates physiology MeSH
- Coleoptera physiology MeSH
- Chironomidae MeSH
- Behavior, Animal physiology MeSH
- Cladocera MeSH
- Culicidae MeSH
- Heteroptera physiology MeSH
- Insecta MeSH
- Isopoda MeSH
- Larva physiology MeSH
- Locomotion MeSH
- Lymnaea MeSH
- Carnivory physiology MeSH
- Mortality MeSH
- Food Chain MeSH
- Predatory Behavior * MeSH
- Fresh Water MeSH
- Body Weight physiology MeSH
- Odonata physiology MeSH
- Aquatic Organisms physiology MeSH
- Anura MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The surface area-to-volume ratio of cells is one of the key factors affecting fundamental biological processes and, thus, fitness of unicellular organisms. One of the general models for allometric increase in surface-to-volume scaling involves fractal-like elaboration of cellular surfaces. However, specific data illustrating this pattern in natural populations of the unicellular organisms have not previously been available. This study shows that unicellular green algae of the genus Micrasterias (Desmidiales) have positive allometric surface-to-volume scaling caused by changes in morphology of individual species, especially in the degree of cell lobulation. This allometric pattern was also detected within most of the cultured and natural populations analysed. Values of the allometric S:V scaling within individual populations were closely correlated to the phylogenetic structure of the clade. In addition, they were related to species-specific cellular morphology. Individual populations differed in their allometric patterns, and their position in the allometric space was strongly correlated with the degree of allometric S:V scaling. This result illustrates that allometric shape patterns are an important correlate of the capacity of individual populations to compensate for increases in their cell volumes by increasing the surface area. However, variation in allometric patterns was not associated with phylogenetic structure. This indicates that the position of the populations in the allometric space was not evolutionarily conserved and might be influenced by environmental factors.
- MeSH
- Phylogeny MeSH
- Micrasterias classification cytology genetics MeSH
- Regression Analysis MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Cell Size MeSH
- Publication type
- Journal Article MeSH
Low resting metabolic rate (RMR) in subterranean rodents used to be considered as a physiological adaptation to cope with stresses of the belowground environment. In African mole-rats (Bathyergidae, Rodentia), RMR was reported to be independent of body mass. This deviation from a general mammalian pattern was considered a precondition for evolution of eusociality, occurring in some bathyergids. We measured metabolic rate and thermoregulation in the silvery mole-rat, Heliophobius argenteocinereus, the only bathyergid genus for which well-supported, comparable data were still missing. Low RMR (154.04 mL O(2) h(-1), which is 82% of the value predicted for a rodent) corresponds to the value expected in a subterranean rodent. Broad range of the thermoneutral zone (25-33 degrees C) and only slightly higher conductance (17.3 mL O(2) h(-1) degrees C(-1), i.e. 112.5% of that predicted for subterranean mammals) indicate that H. argenteocinereus is adapted to lower burrow temperatures rather than to high temperatures. Low RMR in this solitary species, as in other subterranean rodents in general, is probably associated particularly with high energetic cost of foraging. Our results combined with data on other mole-rats show clearly that RMR within the Bathyergidae is mass-dependent.
Alders (Alnus spp.) often dominate at nutrient-poor sites by symbiotic relations with atmospheric nitrogen-fixing bacteria. However, little is known about quantitative relationships between root nodule as a nitrogen acquisition organ and leaf as a carbon acquisition organ. To examine carbon allocation, nitrogen acquisition and net production in nutrient-poor conditions, we examined allocation patterns among organs of shrub Alnus fruticosa at a young 80-year-old moraine in Kamchatka. Slopes of double-log allometric equations were significantly smaller than 1.0 for the root mass, leaf mass and root nodule mass against stem mass, and for the root nodule mass against root mass, indicating that smaller individuals invested disproportionally more biomass into resource-acquiring leaf and root tissues than to supportive tissues compared to older individuals. The slope of allometric equation of root depth against stem height was 0.542, indicating that smaller/younger individuals allocate disproportionally more biomass into root length growth than stem height growth. On the contrary, the root nodule mass isometrically scaled to leaf mass. The whole-plant nitrogen content also isometrically scaled to root nodule mass, indicating that a certain ratio of nitrogen acquisition depended on root nodules, irrespective of plant size. Although the net production per plant increased with the increase in stem mass, the slope of the double-log regression was smaller than 1.0. On the contrary, the net production per plant isometrically increased with leaf mass, root nodule mass and leaf nitrogen content per plant. Since the leaf mass isometrically scaled to root nodule mass, growth of each individual occurred at the leaves and root nodules in a coordinated manner. It is suggested that their isometric increase contributes to the increase in net production per plant for A. fruticosa in nutrient-poor conditions.
- MeSH
- Biomass MeSH
- Nitrogen metabolism MeSH
- Root Nodules, Plant growth & development physiology MeSH
- Plant Roots growth & development physiology MeSH
- Ice Cover MeSH
- Alnus growth & development physiology MeSH
- Plant Stems growth & development physiology MeSH
- Symbiosis MeSH
- Carbon metabolism MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Russia MeSH
