Home About us Contact
|
Home About us Contact | ||
|
|
||
Distances Range (distance + range)
Selected AbstractsInfrequent sporophyte production maintains a female-biased sex ratio in the unisexual clonal moss Hylocomium splendensJOURNAL OF ECOLOGY, Issue 5 2010Knut Rydgren Summary 1.,Sex ratios in unisexual bryophytes are most often female biased, whereas male-biased sex ratios predominate in unisexual seed plants. This ,bryophyte paradox', i.e. that sex ratios are biased in favour of the sex associated with the highest reproductive costs, has remained unexplained. 2.,Analysis of sex-ratio patterns via the influence of sex distribution on population growth rates (,) has not previously been carried out for bryophytes. We used this method to model how variation in sex ratio and sporophyte frequency influences , in the clonal bryophyte Hylocomium splendens. We obtained , by matrix modelling of synthetic experimental populations derived from demographic field data, using a linear two-sex model. 3.,In our set of experimental populations , varied between 1.13 and 1.27 in response to variation in sex ratio and sporophyte frequency, with the highest , obtained for the combination of a very low sporophyte frequency and a slightly female-biased sex ratio. 4.,Our results explain the female-biased sex ratio of H. splendens by the slightly lower survival of and production of vegetative offspring by males than by non-sporophytic females. 5.,Synthesis. According to our models, female dominance is the predicted outcome of low to moderate fertilization success and male performance intermediate between that of sporophytic and of non-sporophytic females. Our results therefore explain how a female-biased sex ratio can be maintained despite higher costs of reproduction in females than in males. In dioecious bryophytes, males and females must grow in close contact for fertilization to take place. Better performance of male ramets than of the female ramets they fertilize also explains how male clones can expand into female clones. A similar performance hierarchy of males and females may occur in unisexual clonal seed plants, but more efficient fertilization systems by pollination prevents the selective advantage of unfertilized females from being realized. This explains why vascular plant populations tend to be male biased. We hypothesise difference in fertilization distance range between sperm and pollen as a simple explanation why ramet level sex ratios are in general male dominated in clonal seed plants and female dominated in clonal bryophytes. [source] Using interpubic distance for sexing manakins in the fieldJOURNAL OF FIELD ORNITHOLOGY, Issue 1 2010Chase D. Mendenhall ABSTRACT Field methods for determining the sex of birds are often limited due to morphometric overlap between sexes, intermediate plumages, seasonality, and reliance on subjective age classification. Interpubic distance, characterized in birds as the distance between the distal ends of the pubic bones, has not been formally tested as a method for determining the sex of birds, despite references among parrot breeders and the frequent use of analogous measurements in mammals. We developed a harmless and easily performed field method for measuring interpubic distance in studies involving bird capture, and compared the interpubic distances of known sex White-ruffed Manakins (Corapipo altera), Orange-collared Manakins (Manacus aurantiacus), and Blue-crowned Manakins (Lepidothrix coronata) to evaluate the possible use of this measurement to determine sex. Using interpubic distance ranges based on 85% confidence intervals where overlap existed between sexes, the sex of 92.8,100% of all manakins in our study was accurately determined with no misclassification. Interpubic distance performed better than plumage-based methods that sexed 74.0% of all individuals and misclassified 1.5%. Using linear discriminant analysis, we developed classification equations that allowed us to accurately determine the sex of all individuals with 100% accuracy using mass and interpubic distance. Additionally, we compared the interpubic distances of female White-ruffed Manakins to evaluate the potential to determine age and reproductive status. Despite an apparent relationship between interpubic distance, age and reproductive status, we concluded that interpubic distance has limited use for determining age and reproductive status due to extensive overlap (31.6,100%), but shows potential in other applications. Based on these results, we endorse the use of interpubic distance to determine the sex of manakins. We encourage further study to develop additional classification equations using different morphometric measurements and to test the efficacy of interpubic distance to determine sex in other bird species. RESUMEN Los métodos del campo para distinguir el sexo de aves son limitados a causa de traslapes de medidas mórfometricas extremas entre sexos, plumajes intermedios, diferencias temporales y/o dependencia en clasificación sujeto de la edad. Distancia interpúbica, caracterizada en aves como la distancia entre los puntos distales de los huesos púbicos, no ha sido formalmente probada como un método para distinguir el sexo de las aves, a pesar de referencias por criadores de loros y uso de métodos similares en mamíferos. Diseñamos un método del campo rápido y sencillo que no tiene riesgo del daño para sacar la distancia interpúbica en estudios que capturan aves. Comparamos la distancia interpúbica de individuos de sexo conocido de Corapipo altera, Manacus aurantiacus, y Lepidothrix coronata para probar el método. Clasificamos correctamente el sexo de 92.8,100% de todos los individuos en este estudio por rangos determinados a través de intérvalos de confianza de 85%. La distancia interpúbica funcionó mejor que un método basado en plumaje, el cual que distinguió el sexo correcto de 74.0% pero falló en clasificar el sexo de 1.5% de los individuos estudiados. Usamos el análisis de discriminación linear para determinar el poder predictivo de la distancia interpúbica, longitud del ala y masa e hicimos ecuaciones de clasificación que distinguieron sexo con un 100% de éxito usando solo masa y distancia interpúbica. Además, comparamos distancia interpúbica de las hembras de C. altera para evaluar el potencial de distinguir edad y estadio reproductivo. A pesar de existir una conexión entre distancia interpúbica, edad y estadio reproductivo, concluimos que la distancia interpúbica es limitada en el contexto de distinguir edad y estadio reproductivo por traslape extensivo (31.6,100%), pero muestra potencial en otras aplicaciones. Basados en estos resultados recomendamos el uso de distancia interpúbica como un método para distinguir sexo de pipridos. Recomendamos más investigación para crear otras ecuaciones de clasificación usando medidas mórfometricas diferentes y probar la eficacia de la distancia interpúbica para distinguir el sexo de otras especies de aves. [source] Exchange Interactions at the Supramolecular Level , Synthesis, Crystal Structure, Magnetic Properties, and EPR Spectra of [Mn(MAC)(TCNQ)2] (MAC = Pentaaza Macrocyclic Ligand; TCNQ·, = Radical Anion of 7,7,8,8-Tetracyano- p -quinodimethane)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2003Augustin M. Madalan Abstract The reaction between [Mn(MAC)(H2O)2]Cl2·4H2O and LiTCNQ (MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene) affords a complex with the formula [Mn(MAC)(TCNQ)2] (1), whose crystal structure has been determined. Its structure consists of neutral mononuclear entities. The manganese(II) ion is heptacoordinated, with a pentagonal bipyramidal geometry. The apical positions are occupied by the TCNQ·, radicals, while the macrocyclic ligand is coordinated at the equatorial positions. The seven Mn,N distances range from 2.273(3) to 2.301(6) Å. The strong intermolecular ,,, stacking interactions between the TCNQ radicals (3.2 Å) leads to weave-like infinite chains, which propagate along the crystallographic c axis. The cryomagnetic investigation of 1 revealed a weak intermolecular antiferromagnetic coupling of the Mn2+ ions (J = ,0.18 cm,1), which is mediated by the diamagnetic (TCNQ)22, pairs resulting from the stacking interactions in the crystal. The intermolecular exchange interaction between the Mn2+ ions was further confirmed by variable temperature EPR spectroscopic measurements [|J| = 0.15(5) cm,1], which have been carried out in both the X and Q bands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Concomitant polymorphic behavior of di-,-thiocyanato-,2N:S;,2S:N -bis[bis(tri- p -fluorophenylphosphine-,P)silver(I)]ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2010Bernard Omondi The structures of two polymorphs, both monoclinic P21/n [polymorph (I)] and P21/c [polymorph (II)], of di-,-thiocyanato-,2N:S;,2S:N -bis[bis(tri- p -fluorophenylphosphine-,P)silver(I)] complexes have been determined at 100,K. In both polymorphs the complex has a dinuclear structure where the silver(I) coordinates to two phosphine ligands and two bridging thiocyanate anions to form complexes with distorted tetrahedral geometry. Polymorph (I) has just one half of the [Ag2(SCN)2{P(4-FC6H4)3}4] molecule at (0, ½, 0) from the origin in the asymmetric unit. Polymorph (II) has one and a half molecules of [Ag2(SCN)2{P(4-FC6H4)3}4] in the asymmetric unit; the half molecule is situated at (0, 1, ½), while the full molecule is located at (1/3, ½, 1/3) from the origin. The Ag,P bond distances range from 2.4437,(4) to 2.4956,(7),Å in both polymorphs. The Ag,S distances are 2.5773,(7),Å in (I) and 2.5457,(5), 2.5576,(5) and 2.5576,(5),Å in (II). The full molecule in polymorph (II) has slightly shorter Ag,N bond distances [2.375,(1) and 2.367,(2),Å] compared with the half molecules in both polymorphs [2.409,(2),Å in (II) and 2.395,(2),Å in (I)]. The two polymorphs are compared using r.m.s. overlay calculations as well as half-normal probability plot analysis. [source] | |||||||||||||