Nutrition is vital for health and immune function in honey bees (Apis mellifera). The effect of diets enriched with bee-associated yeasts and essential oils of Mexican oregano (Lippia graveolens) was tested on survival, food intake, accumulated fat body tissue, and gene expression of vitellogenin (Vg), prophenoloxidase (proPO) and glucose oxidase (GOx) in newly emerged worker bees. The enriched diets were provided to bees under the premise that supplementation with yeasts or essential oils can enhance health variables and the expression of genes related to immune function in worker bees. Based on a standard pollen substitute, used as a control diet, enriched diets were formulated, five with added bee-associated yeasts (Starmerella bombicola, Starmerella etchellsii, Starmerella bombicola 2, Zygosaccharomyces mellis, and the brewers’ yeast Saccharomyces cerevisiae) and three with added essential oils from L. graveolens (carvacrol, thymol, and sesquiterpenes). Groups of bees were fed one of the diets for 9 or 12 days. Survival probability was similar in the yeast and essential oils treatments in relation to the control, but median survival was lower in the carvacrol and sesquiterpenes treatments. Food intake was higher in all the yeast treatments than in the control. Fat body percentage in individual bees was slightly lower in all treatments than in the control, with significant decreases in the thymol and carvacrol treatments. Expression of the genes Vg, proPO, and GOx was minimally affected by the yeast treatments but was adversely affected by the carvacrol and thymol treatments.

Abstract:Distyly is a genetically-controlled polymorphism with two fl oral morphs exhibiting spatial, reciprocal separation between stigmas and anthers; one morph presents styles above anthers, and the other styles below anthers. Distyly is usually linked to a self-incompatibility system that prevents self-pollination and crosses between plants of the same morph, thereby ensuring symmetrical mating and equal morph ratios within populations. This study is the fi rst description of distylous traits in the tropical tree species Cordia dodecandra and C. sebestena from the Yucatan Peninsula. Principal components analysis of fl ower morphological traits identifi ed segregation into two groups with characteristically distylous morphology. Estimation of reciprocal herkogamy using indices showed almost perfect reciprocity in the distance between long and short sexual organs in the two fl ower morphs of both species. Reciprocity between organs was lower in C. dodecandra, suggesting less accuracy in pollen transference between morphs. Self-incompatibility was observed for C. dodecandra, but could not be confi rmed for C. sebestena. However, a 1:1 fl oral morph ratio within the sampled C. sebestena populations suggests the existence of a distylous, self-incompatibility system in this species. Morph distribution in C. dodecandra did not follow a typically distylous distribution, suggesting a disruption in population processes such as seed dispersion and seedling establishment in this species. The reported data confi rm the existence of the distyly syndrome in the two Cordia species. Key words: distyly, morph ratio, reciprocal herkogamy, self-incompatibility.Resumen: La distilia es la separación recíproca entre estigma y anteras, entre plantas de una población, pudiéndose distinguir individuos con fl ores de estilo largo y anteras cortas e individuos con fl ores de estilo corto y anteras largas. Involucrados en este polimorfi smo se encuentran rasgos morfológicos de las fl ores y una auto-incompatibilidad controlada por un sistema de dos alelos que resulta en una proporción de tipos fl orales uno a uno dentro de una población. En este trabajo se explora las características de distilia en dos especies cercanas de árboles tropicales que se distribuyen en la duna costera y en los remanentes de huertos mayas en Yucatán. El análisis de componentes principales mostró la segregación de dos grupos de individuos con diferente morfología fl oral en ambas especies. Los índices de reciprocidad señalaron que la hercogamia entre los órganos largos y cortos se ajusta de forma casi perfecta a lo esperado en un sistema distílico con autoincompatibilidad sexual en Cordia sebestena y C. dodecandra. Sin embargo, en esta última especie se observó una mayor variación en la precisión en la posición de los órganos recíprocos, pudiendo tener consecuencias en la exactitud con la que el polen es depositado sobre el estigma. Las pruebas de incompatibilidad realizadas únicamente en C. dodecandra mostraron que los individuos cuyas fl ores recibieron polen...

Background: Floral nectar and honey vary in sugar concentration, from low concentration in nectar to high concentration in honey. Variation in sugar concentration is a gradient that determines yeast growth and can lead to its ecological niche specialization. Objective: Evaluate the effect of a sugar concentration gradient on the growth kinetics and cell size of yeasts isolated from the floral nectar and honey of Melipona beecheii. Methods: Four strains identified as Metschnikowia koreensis and Sympodiomycopsis paphiopedili, isolated from floral nectar, and Starmerella apicola and Starmerella apicola 2, isolated from honey of Melipona beecheii were grown in artificial media with a gradient of 2, 10, 20, 40 and 60% glucose. We evaluated culture density (cells / µL), growth parameters, and cell size in each strain. Results and Conclusions: Strains isolated from honey had high growth rates at the highest glucose concentrations, while strains isolated from floral nectar grew best at low concentrations. Cell size decreased as glucose concentration increased in all strains. The data supports the hypothesis that sugar concentration gradient is an ecological filter that modifies the growth and morphology of yeasts associated with flowers and honey and leads to niche specialization in yeasts that colonize plant-bee environments.