Canine teeth of bats (Microchiroptera): size, shape and role in crack propagation

Upper canines in microchiropteran bats show a variety of cross-sectional shapes. A consistent feature of all species studied here is that the tooth is edged and not simply round or oval. Prominent sharp edges are positioned in several directions but particularly antero-medially toward the incisors and posteriorly toward the premolars. These edges appear to direct the cracks made in food items to the incisors or to the premolars. A continuous cutting edge is apparent in the occlusal view of the palate running from tip of canine to the ectoloph of the molars. Size and shape analysis indicates that larger bats have slender, rather than stouter, canines for their height, a condition that may be attributable to the nature of the prey. Most bats take prey that have little hard substance imbedded within. The compromises in tooth shape may vary between that of a terrestrial predator with short, conical canines for processing endoskeletal prey to that of a small flying predator with long, slender, edged canines for capturing and processing exoskeletal prey. Unicuspid teeth and how they might function in food break-up have been overlooked to the literature; such a study could lead to an understanding of how more complex teeth function.     

Morphometrics of the callitrichid forelimb: A case study in size and shape

Mosimann and colleagues formulated a technique that distinguishes between size and shape, based on the concept of geometric similarity and the distinction between log size-and-shape and log shape variables. We extend these formulations in an examination of the forelimb of three callitrichid species (adultSaguinus oedipus, Saguinus fuscicollis, andCallithrix jacchus). We employ principal components analysis to explore the relationship between variance explained by size-and-shape versus shape alone. Independence of shape vectors is examined via correlation analysis. Then we use log shape data to construct intersample (species means) and total sample (between all paris of individuals) matrices of average taxonomic distances. These distance matrices are subjected to cluster analysis and principal coordinate ordinations. Results of principal components analysis suggest that after isometric size is removed, there remains sufficient shape information to discriminate among the three taxa. Careful examination and quantification of the relationships between shape and size suggest that size information (e.g., geometric mean) is fundamental for understanding shape differences within and among callitrichid species; in other words, most aspects of forelimb shape are significantly correlated with size. Contrary to conventional wisdom, we also demonstrate that such correlations are not spurious. Ordinations and clustering of log shape distance matrices (based on means and individuals) support the notion that, despite differences in size, the two tamarins are more similar in shape than either is toC. jacchus (despite size similarity betweenS. fuscicollis andC. jacchus). Although shape variation in the forelimb of calliirichids may have a functional component, the phylogenetic signal remains strong and serves to group individuals accordingly.     

Global evaluation of growth in a rural population: comparative analysis of shape and size

In this work the analogies and differences in shape and size between a rural school population (6–14 aged) of the Lozoya-Somosierra region (Madrid) and several recent and past Spanish populations from different environments have been studied. The results show the growth trend as well as the influences of ecological and socioeconomical factors. Paper presented at the 4^th congress of the European Anthropology Association (Florence, Sept. 1984).     

The effect of leaf size on mutual shading and cultivar differences in soybean leaf photosynthetic capacity

This study investigated the basis of the negative relationship between leaf size and photosynthetic rate per unit of area among five cultivars of soybeans. Exposure of developing mainstem leaves to light, and sizes and light saturated photosynthesis rates of those leaves at maturity were compared in cultivars grown in field plots for two years at Beltsville, Maryland, USA. Plants were grown both in stands at 2.5 cm by 1 m spacing and as isolated plants. While cultivar differences in leaf size were large and consistent in both planting arrangements, significant cultivar differences in light saturated photosynthetic rates were found only in plants grown in stands. Similarly, leaf size was significantly correlated with specific leaf weight only for plants grown in stands. The mainstem apex and developing mainstem leaves experienced more severe shading in large-leaved cultivars than in small-leaved cultivars when plants were grown in stands. Thus, cultivar differences in photosynthetic capacity were probably a consequence of differences in the exposure of developing leaves to light.     

Myxosporida (Protozoa): The determination and maintenance of spore size and shape

Data are presented which suggest that the size of fish myxosporidan spores is primarily determined by the parasite's development in the tissues or organ's cavities and the spore's shape is determined by the presence of physiologically and behaviorally suitable fish.     

Phenotypic plasticity in leaf morphology of Crataegus monogyna (Rosaceae): an experimental study with taxonomic implications

Many leaf characters are considered in the taxonomy of Crataegus in Europe, and several have been used in studies of the extent of hybridization in populations of northwest Europe. In such analyses it is assumed that the environmental component of phenotypic variation in such characters is insignificant. We tested this assumption by analysing the variation in the size and shape of leaves borne on clone cuttings of Crataegus monogyna maintained under identical conditions apart from the availability of soil nutrients. The resulting variation among leaves from this single genotype was as great as that observed previously across populations. Furthermore, although most of this variation could not be explained, a part could be attributed to differences in nutrient availability; of nine leaf characters investigated, eight showed significant variation due to this source, and in seven, the variation covaried significantly with nutrient level. The systematic implications of this are briefly explored.     

Pelvic growth: ontogeny of size and shape sexual dimorphism in rat pelves

The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization.     

Specific leaf area and leaf dry matter content as alternative predictors of plant strategies

A key element of most recently proposed plant strategy schemes is an axis of resource capture, usage and availability. In the search for a simple, robust plant trait (or traits) that will allow plants to be located on this axis, specific leaf area is one of the leading contenders. Using a large new unpublished database, we examine the variability of specific leaf area and other leaf traits, the relationships between them, and their ability to predict position on the resource use axis. Specific leaf area is found to suffer from a number of drawbacks; it is both very variable between replicates and much influenced by leaf thickness. Leaf dry-matter content (sometimes referred to as tissue density) is much less variable, largely independent of leaf thickness and a better predictor of location on an axis of resource capture, usage and availability. However, it is not clear how useful dry matter content will be outside northwest Europe, and in particular in dry climates with many succulents.     

Effect of sowing date on the temperature response of leaf emergence and leaf size in barley

Abstract Rate of leaf emergence of barley grown in the field in each of 2 years was affected by sowing date and, where direct comparisons were possible, it was found that leaves on late-sown plants emerged more quickly. Rate of leaf emergence fluctuated throughout the season, slowing almost to zero in the winter. Much of this variation in rate was removed when the number of leaves was plotted against accumulated temperature rather than time. When emergence rates for each sowing were calculated using a common base temperature they were found to be well correlated with rate of change of daylength. However, it was (bund that base temperature as well as temperature response was affected by date of sowing. The pattern of change of size of leaves was also affected by date of sowing. It appeared that in low temperatures and short days, there was no increase in leaf size from leaf position to leaf position. The responses of leaf emergence, extension and final size to date of sowing appear to adapt the plant to grow quickly when sown early but to cease growth and possibly frost-harden at low temperatures.     

Functional interaction between leaf trichomes, leaf wettability and the optical properties of water droplets

Abstract. Because CO₂ diffuses 10000 times more slowly through water than air, there may be strong selective pressure for increased water repellency in terrestrial plant leaves. In the present study, leaf trichomes appeared to have a strong influence on leaf water repellency (i.e. degree of water droplet formation on the leaf surface) as well as the retention of droplets on the leaf. Based upon evaluation of 38 plant species from 21 families, we found that leaves with trichomes were more water repellent, especially where trichome density was greater than 25mm². However, droplet repellency and retention were both high in some species where trichomes entrapped droplets. Finally, the lensing effects of water droplets on leaf surfaces increased incident sunlight by over 20-fold directly beneath individual droplets. These results may have important implications for such processes as stomatal function, whole leaf photosynthesis, and transpiration for a large variety of plant species.     

Polyploidy and cellular mechanisms changing leaf size: comparison of diploid and autotetraploid populations in two species of Lolium

BACKGROUND AND AIMS: Growth and development of plant organs, including leaves, depend on cell division and expansion. Leaf size is increased by greater cell ploidy, but the mechanism of this effect is poorly understood. Therefore, in this study, the role of cell division and expansion in the increase of leaf size caused by polyploidy was examined by comparing various cell parameters of the mesophyll layer of developing leaves of diploid and autotetraploid cultivars of two grass species, Lolium perenne and L. multiflorum. METHODS: Three cultivars of each ploidy level of both species were grown under pot conditions in a controlled growth chamber, and leaf elongation rate and the cell length profile at the leaf base were measured on six plants in each cultivar. Cell parameters related to division and elongation activities were calculated by a kinematic method. KEY RESULTS: Tetraploid cultivars had faster leaf elongation rates than did diploid cultivars in both species, resulting in longer leaves, mainly due to their longer mature cells. Epidermal and mesophyll cells differed 20-fold in length, but were both greater in the tetraploid cultivars of both species. The increase in cell length of the tetraploid cultivars was caused by a faster cell elongation rate, not by a longer period of cell elongation. There were no significant differences between cell division parameters, such as cell production rate and cell cycle time, in the diploid and tetraploid cultivars. CONCLUSION: The results demonstrated clearly that polyploidy increases leaf size mainly by increasing the cell elongation rate, but not the duration of the period of elongation, and thus increases final cell size.     

The scaling of leaf area and mass: the cost of light interception increases with leaf size

For leaves, the light-capturing surface area per unit dry mass investment (specific leaf area, SLA) is a key trait from physiological, ecological and biophysical perspectives. To address whether SLA declines with leaf size, as hypothesized due to increasing costs of support in larger leaves, we compiled data on intraspecific variation in leaf dry mass (LM) and leaf surface area (LA) for 6334 leaves of 157 species. We used the power function LM=alpha LAbeta to test whether, within each species, large leaves deploy less surface area per unit dry mass than small leaves. Comparing scaling exponents (beta) showed that more species had a statistically significant decrease in SLA as leaf size increased (61) than the opposite (7) and the average beta was significantly greater than 1 (betamean=1.10, 95% CI 1.08-1.13). However, scaling exponents varied markedly from the few species that decreased to the many that increased SLA disproportionately fast as leaf size increased. This variation was unrelated to growth form, ecosystem of origin or climate. The average within-species tendency found here (allometric decrease of SLA with leaf size, averaging 13%) is in accord with concurrent findings on global-scale trends among species, although the substantial scatter around the central tendency suggests that the leaf size dependency does not obligately shape SLA. Nonetheless, the generally greater mass per unit leaf area of larger than smaller leaves directly translates into a greater cost to build and maintain a unit of leaf area, which, all else being equal, should constrain the maximum leaf size displayed.     

Developmental plasticity, morphological variation and evolvability: a multilevel analysis of morphometric integration in the shape of compound leaves

The structure of compound leaves provides flexibility for morphological change by variation in the shapes, sizes and arrangement of leaflets. Here, we conduct a multilevel analysis of shape variation in compound leaves to explore the developmental plasticity and evolutionary potential that are the basis of diversification in leaf shape. We use the methods of geometric morphometrics to study the shapes of individual leaflets and whole leaves in 20 taxa of Potentilla (sensu lato). A newly developed test based on the bootstrap approach suggests that uncertainty in the molecular phylogeny precludes firm conclusions whether there is a phylogenetic signal in the data on leaf shape. For variation among taxa, variation within taxa, as well as fluctuating asymmetry, there is evidence of strong morphological integration. The patterns of variation are similar across all three levels, suggesting that integration within taxa may act as a constraint on evolutionary change.