Phenotypic differentiation and pre-mating isolation between allopatric populations of Girardinichthys multiradiatus

Sexual selection may lead to reproductive isolation between populations through divergence in female mate choice, and population differentiation driven by female mate choice is expected to produce pre- but not post-mating isolation. We tested these hypotheses by looking at whether allopatric populations of the Amarillo (Girardinichthys multiradiatus), a sexually dimorphic viviparous fish with effective female choice, (i) have undergone phenotypical differentiation that may be attributed to divergence in female mate choice, and (ii) are already separated by pre- and/or post-mating reproductive barriers. We found substantial divergence in morphological traits which are the target of female mate choice, and in male courtship behaviour. Strong female preferences for homogametic males indicate substantial and symmetric pre-copulatory isolation, but the few successful heterogametic crosses produced in confinement yielded litters of the same size as those produced in homogametic matings, suggesting that post-copulatory isolation between populations is non-existent or weak. It appears that the studied populations have undergone incipient speciation with a pattern that is consistent with speciation driven by sexual selection, yet further work should assess whether divergence in female preferences has promoted male phenotypic differentiation or whether variation in male attributes has driven divergence in female preferences

Female mate preferences on high‐dimensional shape variation for male species recognition traits

En zonas donde las temperaturas son bajas, el problema más común asociado con los calentadores solares de agua es la posibilidad de daños debidos a la congelación del agua. Se propone un calentador solar de aire convencional en combinación con un intercambiador calor aire – agua, en donde el aire caliente del colector cede su calor al agua fría que esta en el sistema de intercambio, perfectamente aislado y fuera de la posibilidad de congelamiento. Este intercambiador esta a su vez conectado con un tanque de almacenamiento. La trasferencias de calor, aire – agua y la circulación del agua del intercambiador al tanque, se realizan por convección natural. La relación entre el área de colección y volumen de los tanques de almacenamiento, es el adecuado. Se analizan los resultados experimentales referidos a las distintas condiciones de funcionamiento del calentador, mostrándose las diferentes temperaturas del mismo, sin extracciones. La simulación numérica con SIMUSOL permite obtener información para optimizar las relaciones entre las tres componentes del sistema.In areas where temperatures are low, the most common problem associated with solar water heaters is the possibility of damage due to water freezing. A conventional solar air heater is proposed in combination with a air - water heat exchanger, where the hot air of the collector gives heat to the cold water that is in the fully isolated exchange system, far from the possibility of freezing. This exchanger is in turn connected to a storage tank. The heat transfer, air – water, and the water circulation from the intercooler to the tank, is achieved by natural convection. The relationship between the collection area and volume of storage vessels is adequate. The experimental results related to several operating conditions of the heater are analyzed, and the different temperatures, without extractions, are shown. The numerical simulation with SIMUSOL makes it possible to obtain information for the optimization of the relationship between the three components of the system.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

The southern churchill, Petrocephalus wesselsi, a new species of mormyrid from South Africa defined by electric organ discharges, genetics, and morphology

East African and south African churchills (Petrocephalus, Mormyridae) were synonymised in 1959 to become members of a single species of subcontinental, southern African distribution, Petrocephalus catostoma (G¨unther, 1866). By comparison with the type material for P. catostoma from the Ruvuma River and P. stuhlmanni from the Ruvu River, both of East African origin, we confirm the South African form of churchill to represent a new species, P. wesselsi, ranging from the northern Limpopo and Incomati systems south to the Pongola River (Natal) as its southern limit.We also compared churchills from the Sabie River (25 S, South Africa, Incomati system) with churchills from the Upper Zambezi River (17 S, Namibia), using electric organ discharges (EODs) and morphology. The duration of an EOD pulse of the South African form (N D 39; 943:2S:E: 18.82 s) is, on average, more than twice that of the Upper Zambezi form (N D 37; 436:6 15:1 s), and the amplitude of the second head-positive phase (P2 phase relative to P1 D 1) significantly weaker (0:133 0:0005 vs. 0:472 0:002 for Upper Zambezi males, 0:363 0:03 for Upper Zambezi females). In contrast to the Upper Zambezi form, the EOD of the South African form exhibits no difference between the sexes. Fish from the two origins differ significantly in 11 out of 14 anatomical characters studied, confirming molecular genetic differentiation on the species level