El intercambio comercial con los países centralmente planificados

Los acontecimientos de política exterior, desde los comienzos de la última década, han hecho presentes en el concierto económico de las naciones un grupo de países que se habían mantenido tradicionalmente al margen de la economía mundial en general y del comercio en particular.Asumida la creciente importancia que este nuevo mercado tiene para el país y sin profundizar en materia tan extensa como la economía centralmente planificada, dada la brevedad y espacio que es necesario guardar, veamos algunos de los aspectos más importantes del intercambio comercial entre países con sistemas económicos y sociales diferentes

Phenology of Scramble Polygyny in a Wild Population of Chrysolemid Beetles: The Opportunity for and the Strength of Sexual Selection

Recent debate has highlighted the importance of estimating both the strength of sexual selection on phenotypic traits, and the opportunity for sexual selection. We describe seasonal fluctuations in mating dynamics of Leptinotarsa undecimlineata (Coleoptera: Chrysomelidae). We compared several estimates of the opportunity for, and the strength of, sexual selection and male precopulatory competition over the reproductive season. First, using a null model, we suggest that the ratio between observed values of the opportunity for sexual selections and their expected value under random mating results in unbiased estimates of the actual nonrandom mating behavior of the population. Second, we found that estimates for the whole reproductive season often misrepresent the actual value at any given time period. Third, mating differentials on male size and mobility, frequency of male fighting and three estimates of the opportunity for sexual selection provide contrasting but complementary information. More intense sexual selection associated to male mobility, but not to male size, was observed in periods with high opportunity for sexual selection and high frequency of male fights. Fourth, based on parameters of spatial and temporal aggregation of female receptivity, we describe the mating system of L. undecimlineata as a scramble mating polygyny in which the opportunity for sexual selection varies widely throughout the season, but the strength of sexual selection on male size remains fairly weak, while male mobility inversely covaries with mating success. We suggest that different estimates for the opportunity for, and intensity of, sexual selection should be applied in order to discriminate how different behavioral and demographic factors shape the reproductive dynamic of populations

Efectos de la cópula y el tamaño del macho sobre el comportamiento de ovipostura en la mosca estercolera Archisepsis diversiformis (Diptera: Sepsidae)

Se evaluó el efecto de la cópula como factor esti­mulante de la oviposición en Archisepsis diversiformis utilizando hembras de dos edades, y en la longevidad de la hembra y en la proporción sexual de la progenie, tomando en cuenta el tamaño de hembra y macho, y el desarrollo de los ovocitos en relación a la edad de la hembra. Se demostró que una demora en copular indujo una demora en oviponer. También hubo similitud en el número de huevos puestos en los diez primeros días después de la cópula, en el número promedio de posturas (grupo de huevos puestos por día) durante toda la vida de una hembra, y en el tiempo promedio transcurrido entre posturas. Otra evidencia del efecto de la cópula en la ovipostura, fue que las hembras que copularon ovipositaron más rápido que las vírgenes. Además, éstas colocaron un número muy bajo (en prome­dio 14) de huevos a partir de los 13 días de edad, mientras que hembras de esta misma edad (que previamente habían copulado a los dos o seis días de edad) colocaron un mayor número (en promedio 75) de huevos. Como en otros estu­dios, el tamaño de la hembra tuvo un efecto significativo sobre el número total de huevos puestos. Sin embargo, el tamaño del macho afectó significativamente la tasa (Nº total de huevos/duración de la vida de la hembra) de ovipostura. Estos datos sugieren la posibilidad de que la selección sexual por elección femenina actúe en hembras de esta especie de mosca.<br>Effects of copulation and male size on the oviposition behavior of the manure fly Archisepsis diversiformis (Diptera: Sepsidae). I evaluated the effect of copulation as a stimulation factor for oviposition of Archisepsis diversiformis by using two different age groups of females. In addition, I tested the effect of copulation on female longevity and progeny sex ratio, taking into account female and male size, and oocyte development in relation to female age. A delay in copulation leads to a delay in oviposition. Females of both age groups started to oviposit between four and five days after copulation. The number of eggs that were laid during the first ten days after copulation, the average number of ovipositions (number of eggs laid per day) during the female’s life, and the average time between ovipositions were all similar. I found further evidence for the effect of copulation on oviposition: when females copulate, they oviposited faster than virgin females. In addition, these females laid a lower number of eggs after the age of 13 days, while females of the same age (that have copulated before, when they were two or six days old) laid a higher number of eggs (an average of 75 eggs). Oocytes in virgin females became larger with age; 57 % of the variation in the number of eggs laid by females depends on female’s longevity. As in other studies, female size had an effect on the total number of eggs laid. However, male size significantly affected the oviposition rate (total number of eggs/female longevity). Females tended to have a higher oviposition rate after copulating with larger males. These data suggest that for this fly species, sexual selection through female choice might be occurring. Rev. Biol. Trop. 57 (Suppl. 1): 239-250. Epub 2009 November 30

Effects of copulation and male size on the oviposition behavior of the manure fly Archisepsis diversiformis (Diptera: Sepsidae).

Se evaluó el efecto de la cópula como factor estimulante de la oviposición en Archisepsis diversiformis utilizando hembras de dos edades, y en la longevidad de la hembra y en la proporción sexual de la progenie, tomando en cuenta el tamaño de hembra y macho, y el desarrollo de los ovocitos en relación a la edad de la hembra. Se demostró que una demora en copular indujo una demora en oviponer. También hubo similitud en el número de huevos puestos en los diez primeros días después de la cópula, en el número promedio de posturas (grupo de huevos puestos por día) durante toda la vida de una hembra, y en el tiempo promedio transcurrido entre posturas. Otra evidencia del efecto de la cópula en la ovipostura, fue que las hembras que copularon ovipositaron más rápido que las vírgenes. Además, éstas colocaron un número muy bajo (en promedio 14) de huevos a partir de los 13 días de edad, mientras que hembras de esta misma edad (que previamente habían copulado a los dos o seis días de edad) colocaron un mayor número (en promedio 75) de huevos. Como en otros estudios, el tamaño de la hembra tuvo un efecto significativo sobre el número total de huevos puestos. Sin embargo, el tamaño del macho afectó significativamente la tasa (Nº total de huevos/duración de la vida de la hembra) de ovipostura. Estos datos sugieren la posibilidad de que la selección sexual por elección femenina actúe en hembras de esta especie de mosca.I evaluated the effect of copulation as a stimulation factor for oviposition of Archisepsis diversiformis by using two different age groups of females. In addition, I tested the effect of copulation on female longevity and progeny sex ratio, taking into account female and male size, and oocyte development in relation to female age. A delay in copulation leads to a delay in oviposition. Females of both age groups started to oviposit between four and five days after copulation. The number of eggs that were laid during the first ten days after copulation, the average number of ovipositions (number of eggs laid per day) during the female’s life, and the average time between ovipositions were all similar. I found further evidence for the effect of copulation on oviposition: when females copulate, they oviposited faster than virgin females. In addition, these females laid a lower number of eggs after the age of 13 days, while females of the same age (that have copulated before, when they were two or six days old) laid a higher number of eggs (an average of 75 eggs). Oocytes in virgin females became larger with age; 57 % of the variation in the number of eggs laid by females depends on female’s longevity. As in other studies, female size had an effect on the total number of eggs laid. However, male size significantly affected the oviposition rate (total number of eggs/female longevity). Females tended to have a higher oviposition rate after copulating with larger males. These data suggest that for this fly species, sexual selection through female choice might be occurrin

Anacroneuria farallonensis (Plecoptera : Perlidae) una nueva especie para Colombia.

Se describe a Anacroneuria farallonensis (Plecoptera: Perlidae) nueva especie, basada en un ejemplar macho colectado en el Parque Nacional Natural de los Farallones, departamento del Valle del Cauca, Colombia

Variance in male mating success in <i>L. undecimlineata</i>.

<p>Estimates and bootstrap 95% confidence intervals of variance in mating success among successful males (<i>V</i>_harem) and among all males (<i>V</i>_mates) in each period (squares) and for the whole season (circles). <b>A–D</b>) observed values (open markers) and values expected under random mating (solid markers). <b>E–H</b>) the ratio between observed and randomly expected values (O/RE) from the null model of each estimate. The dashed horizontal lines at y = 1 represent no difference between observed and randomly expected values (O/RE  = 1). Variances in male mating success among successful males (<i>V</i>_harem), and among all males (<i>V</i>_mates) were significantly higher than expected under random mating for period 2, barely higher for period 1, and not different or even significantly lower than random expectations in period 3.</p

Covariance across temporal intervals in male mating success and sex ratio in <i>L. undecimlineata.</i>

<p>Observed values represented by open markers, randomly expected values represented by solid markers, 95% bootstrap confidence intervals represented by lines and random expectations represented by dashed horizontal line at y = 0. <b>A</b>) Covariance across temporal intervals in male mating success which includes the temporal and spatial variation of sex ratio (<i>Cov</i>_(phen) ×10⁻²). Only the observed value for period 4 differed from random expectations although no differences were observed among periods or to the whole season. <b>B</b>) Sex ratio (R), the number of receptive females to total males; there were no significant differences among periods while the value for the whole season was significantly different from periods 3 and 4.</p

The opportunity for sexual selection in <i>L. undecimlineata</i>.

<p>Estimates and bootstrap 95% confidence intervals of the opportunity for sexual selection among successful males (<i>I</i>_harem), the opportunity for sexual selection (<i>I</i>_mates) derived from the relationship between the number of mated females per successful male (<i>m</i>), the variance in mating success among successful males (<i>V</i>_harem) and among all males (<i>V</i>_mates); its value adjusted (<i>I</i>_mates(adj)) to sex ratio (R) mean spatial female crowding around males (<i>m*</i>), and the opportunity for sexual selection derived from female receptive phenology (<i>I</i>_mates(phen)) in each period (squares) and for the whole season (circles). <b>A–D</b>) observed values (open markers) and values expected under random mating (solid markers). <b>E–H</b>) the ratio between observed and randomly expected values (O/RE) from the null model of each estimate. The dashed horizontal lines at y = 1 represent no difference between observed and randomly expected values (O/RE  = 1). All four estimates of <i>I</i> for period 2, and two (<i>I</i>_mates(adj) and <i>I</i>_mates(phen)) for period 3, are significantly higher than random expectations. The opportunity for sexual selection for both estimates that factor in sex ratio (<i>I</i>_mates(adj) and <i>I</i>_mates(phen)) resulted in significantly higher randomly expected values for periods 1, 2 and 3. Relatively fewer mating events in period 4 due to lower density in the population and a decrease in reproductive behavior resulted in much larger confidence intervals.</p

Estimates of the opportunity for sexual selection based on female reproductive phenology in <i>L. undecimlineata</i>.

<p>Estimates of the opportunity for sexual selection based on female reproductive phenology in <i>L. undecimlineata</i>.</p