The fig pollinating wasps (Hymenoptera: Agaonidae) have obligate arrhenotoky and a breeding structure that fits local mate competition (LMC). it has been traditionally assumed that LMC organisms adjust the sex ratio by laying a greater proportion of male eggs when there is superparasitism (several foundresses in a host). We tested the assumption with two wasp species, Pegoscapus silvestrii, pollinator of Ficus pertusa and Pegoscapus tonduzi, pollinator of Ficus eximia (= F. citrifolia), in the Central Valley of Costa Rica. Total number of wasps and seeds were recorded in individual isolated naturally colonized syconia. There was a constant additive effect between the number of foundresses and the number of males produced in the brood of a syconium, while the number of females decreased. Both wasp species seem to have precise sex ratios and probably lay the male eggs first in the sequence, independently of superparasitism and clutch size: consequently, they have a non-random sex allocation. Each syconium of Ficus pertusa and of F. eximia colonized by one foundress had similar mean numbers of females, males, and seeds. The two species of wasps studied do not seem to adjust the sex ratio when there is superparasitism. Pollinating fig wasp behavior is better explained by those models not assuming that females do mathematical calculations according to other females' sex ratios, size, number of foundresses, genetic constitution, clutch size or environmental conditions inside the syconium. Our results are in agreement with the constant male number hypothesis, not with sex ratio games. Rev. Biol. Trop. 57 (3): 605-621. Epub 2009 September 30.
Revista electrónica semestral RESUMEN: El objetivo de este estudio fue investigar la mortalidad por causas externas y por enfermedades entre inmigrantes nicaragüenses jóvenes en Costa Rica y compararla con la respectiva población de jóvenes costarricenses. El estudio se enfocó en personas con edades de 15 a 35 años, debido a la importancia relativa de las muertes por causas externas en ese grupo de edad. Las defunciones (numeradores) y la población (denominadores), que fueron obtenidas del X Censo de Población y Vivienda 2000, se utilizaron para calcular las tasas de mortalidad por 100,000 habitantes. El riesgo relativo (RR) resulta de dividir las tasas de mortalidad estandarizadas de las dos poblaciones. Se encontró que alrededor del 66% de las defunciones de inmigrantes nicaragüenses son por causas externas, versus el 57% de su contraparte costarricense. Los inmigrantes tienen riesgos relativos (RR) mayores de mortalidad por causas externas que su correspondiente costarricense (homicidios RR=2.00, otros accidentes RR=1.70 y accidentes vehiculares RR=1.17). En particular, se destaca que los inmigrantes nicaragüenses tienen el doble de riesgo de morir a causa de homicidios que su contraparte costarricense. Palabras Clave: Mortalidad, muertes por causas externas, muertes por enfermedades, inmigrantes, Costa Rica.
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