Reproductive potential of a vole pest (Arvicola scherman) in Spanish apple orchards

Fossorial water voles, Arvicola scherman, feed on tree roots causing important damages in European apple orchards. Since the intensity of crop damage produced by rodents ultimately depends on their inherent capacity to increase their population, the main goal of this study was to determine the reproductive potential of the subspecies A. scherman cantabriae in apple orchards from Asturias (NW Spain), where voles breed over the whole year. Our results were compared with those reported for the subspecies A. scherman monticola from the Spanish Pyrenees (where reproduction ceases in winter). Sexual characteristics, body condition, relative age class and number of embryos were recorded from 422 females caught in apple orchards along two years. We found pregnant females all along the year, which were able to produce a high number of litters per year (7.30) although litter size was relatively moderate (first year: 3.87 embryos/female; second year: 3.63 embryos/females). The potential number of pups per female and year (first year: 28.25; second year: 26.50) was substantially higher than that reported for Pyrenean voles, what is probably related with differences in the length of the breeding season and in life histories between subspecies. In our population, the number of implanted embryos correlated positively with the body condition of the mother. Our results reveal that management efforts should not be seasonal as they used to be so far and invite to explore the physiological consequences of management practices

Postnatal ontogeny of the femur in fossorial and semiaquatic water voles in the 3D-shape space

Altres ajuts: Acord transformatiu CRUE-CSICWater voles of the genus Arvicola constitute an excellent subject to investigate to which extent function affects postnatal developmental growth of limb structures in phylogenetically close species. We performed a comparative analysis of postweaning femur form changes between Arvicola sapidus (semiaquatic) and Arvicola scherman (fossorial) using three-dimensional landmark-based geometric morphometrics. In both species, we observed greater femur robustness in juvenile individuals than in adult ones, probably due to the accommodation of high loads on the bone during initial locomotor efforts. Significant interspecific differences were also found in the femur size and shape of adult specimens, as well as in the postnatal allometric and phenotypic trajectories. In terms of phenotypic variation, fossorial water voles show relatively wider third and lesser trochanters, and greater femur robustness than A. sapidus, characters associated to the digging activity. In contrast, A. sapidus displays a slight increase of the greater trochanter in comparison with A. scherman, which is seemingly an adaptive response for enhancing propulsion through the water. Results evidence that certain morphological traits and differences between A. sapidus and A. scherman in the allometric and phenotypic trajectories of the femur are associated with their different locomotor mode

Morphometrics of genus Caluromys (Didelphimorphia : Didelphidae) in northern South America

We reviewed the morphometric relationships between different forms of the woolly opossum, genus Caluromys, in northern South America by means of univariate and multivariate analyses of skull characters. Results revealed that specimens from Trinidad and northern Venezuela differ substantially in size and shape from other representatives of the genus. Thus, we propose that they should be attributed to Caluromys trinitatis rather to C. philander. Consequently, the specific name given by Thomas (1894, 1903) should be reapplied. The morphotype leucurus, also attributed by Thomas (1904) to C. trinitatis, has an intermediate morphology, resembling C. philander in size but C. trinitatis in shape. Therefore, we were unable to assign it to a specific taxon. Nevertheless, these differences allowed us to consider leucurus as a valid taxonomic entity. Caluromys derbianus and C. lanatus show similar skull sizes but these two species clearly differ in shape, the latter being more phenetically related to C. philander than to any other Caluromys form.Se revisan las relaciones morfométricas entre distintos morfotipos del género Caluromys, presentes en el norte de Suramérica, mediante análisis univariantes y multivariantes de caracteres craneales. Los resultados obtenidos indican que los ejemplares de Trinidad y del norte de Venezuela difieren substancialmente en el tamaño y la forma del cráneo respecto a las demás muestras analizadas. En consecuencia, se sugiere atribuir dichos ejemplares a Caluromys trinitatis y no a C. philander, recuperando así el nombre específico bajo el que fueron descritos por Thomas (1984, 1903). El morfotipo leucurus, considerado por Thomas (1904) como una subespecie de trinitatis, presenta una morfología intermedia, asemejándose a C. philander en tamaño y a C. trinitatis en forma. Estas características no permiten realizar un diagnóstico específico inequívoco de los ejemplares atribuidos a dicho morfotipo. No obstante, debido a sus características craneales, se considera leucurus como una entidad con validez taxonómica. Los resultados obtenidos corroboran la similitud existente entre C. derbianus y C. lanatus en cuanto al tamaño craneal. Sin embargo, ambas especies difieren notablemente en forma, mostrando en este caso C. lanatus una mayor proximidad fenética respecto a C. philander que respecto a cualquier otro representante del género

Variación craneométrica de Rhipidomys latimanus venezuelae (Muridae, Sigmodontinae)

Se estudian las características craneométricas del morfotipo neotropical de rata arborícola Rhipidomys latimanus venezuelae (sensu Tribe, 1996) atendiendo al sexo, edad relativa y crecimiento postnatal. Los análisis estadísticos efectuados revelaron que se trata de una subespecie sexualmente monomórfica y que el criterio de agrupación de las clases de edad propuesto por Tribe (1996) para Rhipidomys no debe hacerse extensivo a todos los representantes del género. Los análisis de regresión demostraron que, durante el periodo postnatal, la región facial experimenta de manera general un crecimiento significativamente mayor que la caja craneana. Esta variación alométrica cabe asociarla al rápido desarrollo de la porción encefálica del cráneo durante la fase embrionaria y a la regulación de la morfología esquelética que ejercen especialmente los músculos temporal, masetero y pterigoides.The craniometrical characteristics of the Neotropical climbing mouse Rhipidomys latimanus venezuelae (sensu Tribe, 1996), according to sex, relative age, and postnatal growth were investigated. Results showed that it is a sexually monomorfic subspecies and that the criterion used by Tribe (1996) to group age classes in Rhipidomys cannot be extended to all representatives of this genus. Regession analyses revealed that during postnatal period the facial region of the skull grows, in general, more than the braincase. This allometric variation is connected with the fast development of the encephalic portion of the skull during the embryonary growth and the regulation of the skeletal morphology caused especially by the temporal, maseter, and pterigoid muscles

Common distribution patterns of marsupials related to physiographical diversity in Venezuela

The aim of this study is to identify significant biotic regions (groups of areas with similar biotas) and biotic elements (groups of taxa with similar distributions) for the marsupial fauna in a part of northern South America using physiographical areas as Operational Geographical Units (OGUs). We considered Venezuela a good model to elucidate this issue because of its high diversity in landscapes and the relatively vast amount of information available on the geographical distribution of marsupial species. Based on the presence-absence of 33 species in 15 physiographical sub-regions (OGUs) we identified Operational Biogeographical Units (OBUs) and chorotypes using a quantitative analysis that tested statistical significance of the resulting groups. Altitudinal and/or climatic trends in the OBUs and chorotypes were studied using a redundancy analysis. The classification method revealed four OBUs. Strong biotic boundaries separated: i) the xerophytic zone of the Continental coast (OBU I); ii) the sub-regions north of the Orinoco River (OBU III and IV); and those south to the river (OBU II). Eleven chorotypes were identified, four of which included a single species with a restricted geographic distribution. As for the other chorotypes, three main common distribution patterns have been inferred: i) species from the Llanos and/or distributed south of the Orinoco River; ii) species exclusively from the Andes; and iii) species that either occur exclusively north of the Orinoco River or that show a wide distribution throughout Venezuela. Mean altitude, evapotranspiration and precipitation of the driest month, and temperature range allowed us to characterize environmentally most of the OBUs and chorotypes obtained

Variational modularity at the cell level : insights from the sperm head of the house mouse

Background: Modularity is an important feature in the evolvability of organisms, since it allows the occurrence of complex adaptations at every single level of biological systems. While at the cellular level the modular organization of molecular interactions has been analyzed in detail, the phenotypic modularity (or variational modularity) of cell shape remains unexplored. The mammalian spermatozoon constitutes one of the most complex and specialized cell types found in organisms. The structural heterogeneity found in the sperm head suggests an association between its inner composition, shape and specificity of function. However, little is known about the extent of the connections between these features. Taking advantage of the house mouse sperm morphology, we analyzed the variational modularity of the sperm head by testing several hypotheses related to its structural and functional organization. Because chromosomal rearrangements can affect the genotype-phenotype map of individuals and thus modify the patterns of covariation between traits, we also evaluate the effect of Robertsonian translocations on the modularity pattern of the sperm head. Results: The results indicated that the house mouse sperm head is divided into three variational modules (the acrosomal, post-acrosomal and ventral spur module), which correspond to the main regions of the cytoskeletal mesh beneath the plasma membrane, i.e., the perinuclear theca. Most of the covariation is concentrated between the ventral spur and the acrosomal and post-acrosomal modules. Although the Rb fusions did not alter the main modularity pattern, they did affect the percentages of covariation between pairs of modules. Conclusions: The structural heterogeneity of the cytoskeleton is responsible for the modular organization of the sperm head shape, corroborating the role that this structure has in maintaining the cell shape. The reduction in percentages of shape covariation between pairs of modules in Rb sperms suggests that chromosomal rearrangements could induce changes in the genotype-phenotype map. Nevertheless, how these variations affect sperm fertilization success is yet to be elucidated

Projecte d'atlas electrònic del crani : innovació docent a les pràctiques de vertebrats

L'assignatura de Vertebrats s'imparteix dins el segon cicle de la llicenciatura de Biologia, tant a la Universitat Autònoma de Barcelona com a la Universitat de Barcelona. La matèria pròpia d'aquesta assignatura es caracteritza per la seva amplitud temàtica, així com per la dificultat intrínseca que comporten els continguts referents a aspectes morfològics. De manera particular, una de les estructures que per la seva complexitat sempre resulta difícil d'assimilar per part dels estudiants és el crani. Tradicionalment, durant les pràctiques de laboratori els alumnes examinen i interpreten diferents peces anatòmiques des del punt de vista comparat i és freqüent que, degut a la quantitat de material a consultar i a la poca durada relativa de les sessions pràctiques, no hi hagi temps suficient per poder assimilar amb profunditat certes observacions referents al crani. Per tal de facilitar la comprensió d'aquesta estructura, professors de les Universitats esmentades estan elaborant, a partir fonamentalment de material i imatges pròpies, un atlas electrònic del crani, en el que es presta una atenció molt particular al binomi estructura-funció, relació que facilita notablement la interpretació morfològica des dels punts de vista evolutiu i adaptatiu. Mitjançant aquest atlas s'esperen obtenir resultats positius en els següents aspectes: i) una millor comprensió del pla estructural del crani; ii) un increment en la capacitat de síntesi dels alumnes; iii) completar l'aprenentatge teòric amb observacions de les peces anatòmiques, constatant la seva modificació al llarg de l'evolució; iv) una millora de la qualitat docent i de la coordinació del professorat que imparteix l'assignatura. Un cop completades les diferents seccions de l'atlas, es té previst programar una sèrie d'activitats d'autoavaluació sobre la informació proporcionada, així com realitzar una enquesta a l'alumnat per tal de valorar i, en el seu cas, millorar el material presentat

Effect of chromosomal reorganizations on morphological covariation of the house mouse mandible: insights from a Robertsonian system of Mus musculus domesticus

Morphological integration and modularity depend on genetic covariation between traits, which emerges from pleiotropic effects of single loci and genetic linkage between loci. Since chromosomal reorganizations alter meiotic recombination, they might modify groups of linked genes and entail the fixation of new alleles with new pleiotropic effects. As a result, they could contribute to the intraspecific variation of the covariance structure of morphological traits. Although the mouse mandible has long been studied in terms of development and evolution, little is known about how its covariance structure varies in natural populations with chromosomal reorganizations. Consequently, here we analyzed the magnitude and patterns of morphological covariation of mandible shape in groups of mice with different karyotypes from a Robertsonian system of Mus musculus domesticus. Results: The organization of the mouse mandible into two main modules was confirmed in all chromosomal groups, since RV coefficients for the corresponding subdivision of landmarks were always significant. However, substantial variation in the magnitude of integration was detected between groups, especially when the effect of allometry was not removed. A significant positive correlation between differences in magnitude of integration of the symmetric component of shape and karyotypic distances between groups was detected when not correcting for size. Moreover, the degree of dependence of symmetric shape variation on size showed a negative association with the chromosome number and a positive association with the magnitude of integration. All groups showed similar patterns of morphological integration of the mandible, especially regarding the symmetric component of shape. However, the display of landmark displacements and the computation of vector angles highlighted some differences. In addition, distances between groups in terms of covariation matrices of the symmetric component were positively correlated with geographic distance. Conclusions: Robertsonian translocations do not alter the organization of the mouse mandible into two main modules, but do affect the magnitude of integration between them. This effect is mainly due to changes in the allometric relationship. In the 'Barcelona' Robertsonian system, geographically structured sources of variation seem to affect the patterns of integration by producing parallel variation in separate developmental pathways. Overall, our results suggest that Robertsonian translocations could play a role in intraspecific differentiation processes by producing changes in the covariance structure of morphological traits

La asimetría bilateral como indicador de inestabilidad del desarrollo

The effect that developmental instability (DI) has on the asymmetry of bilateral structures in animals and plants is a topic of increasing interest in many ecological and evolutionary contextsEl efecto que la inestabilidad del desarrollo (ID) tiene sobre la asimetría de las estructuras bilaterales de animales y plantas es un tema de interés creciente en muchos contextos ecológicos y evolutivos