Functional similarity and competitive symmetry control productivity in mixtures of Mediterranean perennial grasses.

Competition is a major factor structuring plant communities and controlling their productivity. The functional similarity between the interacting species and the context resource availability are assumed to be most critical factors that modulate the strength, sign, and outcome of plant competition, yet their roles and interactions are subjected to debate. In a glasshouse experiment, we constructed monocultures and bi-specific cultures of three common perennial grasses of Mediterranean drylands, the short grass Brachypodium retusum and the tussock grasses Stipa tenacissima and Lygeum spartum, and investigated how the functional similarity between these species modulate their interactions and culture productivity under contrasting levels of water availability. Regardless the degree of functional similarity between the interacting species, B. retusum consistently exhibited a greater competitive ability than the other two species, followed by L. spartum, and with S. tenacissima behaving as the weakest competitor. Bi-specific cultures of B. retusum and either L. spartum or S. tenacissima produced higher biomass than the average biomass of the respective monocultures (i.e. overyielding), whereas the combination of the most similar species, L. spartum-S. tenacissima, which exhibited the highest competition symmetry (i.e., the more similar mutual impact), did not show any significant overyielding. Higher water availability increased productivity and promoted transgressive overyielding for the most dissimilar species, B. retusum and L. spartum, which however exhibited intermediate competition asymmetry. This study calls attention to the thin line between differences in functional traits and competition asymmetry that could eventually lead to either competitive exclusion or resource partitioning and coexistence.

Anomalías congénitas urológicas: descripción epidemiológica y factores de riesgo asociados en Colombia 2001-2004 / Congenital urological anomalies: epidemiological description and associated risk factors in Colombia 2001-2004

OBJETIVO: Determinar la incidencia de anomalías congénitas urológicas en Colombia y estudiarsu asociación con factores de riesgo maternos.MÉTODOS: Se realizó una revisión de los registros generados por el ECLAMC (Estudio Colaborativo Latinoamericanode Malformaciones Congénitas) en Colombiaentre junio de 2001 y diciembre de 2004. Se seleccionaron los registros positivos para anomalías congénitas urológicas. Se realizaron cálculos de incidenciapara cada una de las entidades y estimación de odds ratio para 11 variables maternas.RESULTADOS: Se encontraron 83 registros positivos para alguna malformación congénita urológica, estableciendouna incidencia de 0,43%. La tasa (x 10.000 nacimientos) obtenida para cada una de las malformacionesfue: hipospadias 17,7; criptorquidia 13,3; hidronefrosis 2,6; enfermedad renal quística 2,6; genitalesambigüos 2,6; agenesia renal unilateral 1,3; micropene1,9; agenesia renal bilateral 0,7; persistencia uraco 0,3. Se encontró un riesgo incrementado para defectos renales con parto pretérmino, odds ratio (OR)= 3,66; 95% IC [1,13-13,82] y presencia de enfermedadcrónica en la madre OR= 6,18; 95% IC [1,09-34,98]. Una asociación determinística se encontró con consanguinidad entre padres. Las asociaciones positivaspara defectos genitales fueron bajo peso neonatal OR= 4,07; 95% IC [2,00-8,25], parto pretérmino OR= 3,80; 95% IC [1,87-7,72], existencia de malformado en la familia OR= 2,30; 95% IC [1,02-5,25], y tabaquismodurante el embarazo OR= 5,36; IC [1,01-28,51]. Una asociación determinística se encontró con la ingesta de alcohol durante el embarazo.CONCLUSIONES: La tasa de anomalías urológicas en Colombia es considerablemente más baja en relación con estadísticas europeas y norteamericanas. El peso al nacimiento es el principal factor de riesgo para anomalíascomo hipospadias y criptorquidia. La consanguinidadentre padres y la ingesta de alcohol durante el embarazo son determinantes en el riesgo de anomalías renales y genitales, respectivamente. Variables como el tabaquismo durante el embarazo y enfermedades crónicasen la madre deben ser más profundamente estudiadasen el futuro para determinar su papel en la etiología de estos defectos

OBJECTIVE: To determine the incidence of congenital anomalies of the urinary tract in Colombia and study their association with maternal risk factors. METHODS: We performed a register based, case control study using the data from the ECLAMC (Colaborative Latinoamerican Study for Congenital Malformations) in Colombia, between June, 2001 and December, 2004. Positive Registries for any urological anomaly wereselected. Calculations for the incidence of each abnormality were done. Odds ratio were estimated for 11 maternal variables.RESULTS: 83 positive registries were found. The established incidence was 0,43%. These anomalies accounted for 9,4% of the total of malformations. The obtained rate (x 10.000 births) for each anomaly was: hypospadias 17,7; chryptorchidism 13,3; hydronephrosis 2,6; cystic renal disease 2,6; undeterminate sex 2,6; unilateralrenal agenesis 1,3; micropenis 1,9; bilateral renalagenesis 0,7; patent urachus 0,3. The risk for renaldefects increased with preterm birth, odds ratio OR= 3,66; 95% IC [1,13-13,82] and maternal chronicdisease OR= 6,18; 95% CI [1,09-34,98]. A deterministicassociation was found with consanguinity between the parents. The positive associations for genital defects were: low birth weight OR= 4,07; 95% CI [2,00-8,25], preterm birth OR= 3,80; 95% CI [1,87-7,72], presence of malformated individuals in the family OR= 2,30; 95% CI [1,02-5,25], and smoking during pregnancy OR= 5,36; IC [1,01-28,51]. A deterministic association was found with alcohol ingestion during pregnancy.CONCLUSIONS: The prevalence of anomalies of the urinary tract in Colombia is considerably lower in comparisonwith european and northamerican statistics. The birth weight is the most important risk factor for anomalies like hypospadias and chriptorchidism. Consanguinity between the parents and alcohol ingestion during the pregnancy are determinant on the risk for renal and genital anomalies, respectively. Variables like smoking during pregnancy and chronic maternal disease must be deeply explored in the future to determine their role in the etiology of these defects