Por que Melipona scutellaris (Hymenoptera, Apidae) forrageia sob alta umidade relativa do ar?

Abstract

ABSTRACT. Why do the stingless bee Melipona scutellaris (Hymenoptera, Apidae) forage at high relative air humidity? There are evidences that air temperature and relative humidity exerts influence on the flight activity of the social stingless bees (Meliponini). Particularly, the relatively large species of Melipona Illiger, 1806 would present variation in daily foraging activity very close to variation in relative humidity. In this study, we argue that the relative humidity is a confounding variable. In this same line of argumentation, it was also examined the role of pollen harvest on daily rhythm of foraging. The robust Melipona scutellaris (Latreille, 1811) was used as a model and the flight activity and pollen harvest along the day were measured in 12 colonies (4 colonies/habitat), in three types of habitats with varying rainfall, within the natural distribution range of this species (tropical rainforest, seasonal tropical forest and transition of tropical forest-savannah). Most of flight activity occurs during morning time in the three habitats. Colony foraging is high in the very early morning when the relative humidity is also high, and often associated with peaks of pollen harvest. Flight activity decreases abruptly during the high temperatures around noon time. The relationship between the flight activity and the relative humidity was highly significant and linear, in contrast to the unimodal and significant relationship with temperature. The relationship between the flight activity and the relative humidity is assumed to be contingent within humid tropical habitats, considering the daily microclimate variation and pollen foraging patterns. In particular, the latter pattern supports the hypothesis of temporal partitioning of pollen sources. KEYWORDS.Temporal resource partitioning, pollen foraging, physiological constraint, stingless bees. RESUMO. Há evidências de que a temperatura do ar e a umidade relativa afetam a atividade de voo de espécies de abelhas sociaisMeliponini. Em particular, as espécies grandes do gênero Melipona Illiger, 1806 responderiam de maneira mais estreita à variação na umidade relativa. Neste estudo defende-se o argumento de que a umidade relativa seja uma variável de confusão. Nesta linha de argumentação, também foi analisado o papel da coleta de pólen sobre o ritmo diário de forrageio. A robusta Melipona scutellaris (Latreille, 1811) foi usada como modelo e a atividade diária de voo e de forrageio de pólen foi medida em 12 colônias (4 colônias/hábitat), em três tipos de hábitats, que variam principalmente quanto à pluviosidade, na área de distribuição natural desta espécie (Floresta Pluvial, Floresta Sazonal e Transição Floresta Tropical-Cerrados). A maioria da atividade de voo acontece durante a manhã. A atividade de forrageio das colônias foi mais elevada nas primeiras horas do alvorecer, quando a umidade relativa também era alta, frequentemente associada a picos de coleta de pólen. A atividade de voo decresceu abruptamente durante as temperaturas altas ao redor do meio dia. A...

Influence of seasonal changes in daily activity and annual life cycle of Geotrigona mombuca (Hymenoptera, Apidae) in a Cerrado habitat, São Paulo, Brazil

“…Analysing the previous studies performed about Meliponini flight activity, Silva et al (2011) noted a consensus on small bees of this group being different from the foraging activity profile of Melipona large species, in similar flight conditions. Small size species show a high surface/ volume relationship, and so their metabolism is directly related to climate variations (Oliveira, 1973; Iwama, 1977; Silva et al, 2011).…”

“…Analysing the previous studies performed about Meliponini flight activity, Silva et al (2011) noted a consensus on small bees of this group being different from the foraging activity profile of Melipona large species, in similar flight conditions. Small size species show a high surface/ volume relationship, and so their metabolism is directly related to climate variations (Oliveira, 1973; Iwama, 1977; Silva et al, 2011). Indeed, temperature and relative humidity, or both, are considered as influential factors on flight activity of several stingless bees of small size, including Tetragonisca angustula (Latreille, 1811), Plebeia saiqui (Friese, 1900), Plebeia droryana (Friese, 1900), Plebeia remota (Holmberg, 1903), Plebeia emerina Friese, Trigona carbonaria (Smith, 1854), T. hyalinata (Lepeletier, 1836) and Plebeia pugnax Moure (Oliveira, 1973;Iwama, 1977;KleinertGiovannini, 1982;Imperatriz-Fonseca et al, 1985;Heard & Hendrikz, 1993;Hilário et al, 2001;Pick & Blochtein, 2002;Contrera et al, 2004).…”

“…There is evidence of a temporal division in the exploitation of floral resources throughout the day, based on body size and the consequent relationships with flight activity (Bruijn & Sommeijer, 1997;Hilário et al, 2000;Souza et al, 2006;Silva et al, 2011). The idea is that smaller size bees may also benefit from resources left by large size competitors, and this could partially explain the constancy of pollen collection during the day (Silva et al, 2011). An alternative hypothesis would be the forager specialization in different kinds of material transported.…”

“…Data from the total number of samples were analysed to verify the null hypothesis that the number of exiting bees is equal to the entering bees (from now on determined as entrance number), using the NPAR test Wilcoxon non-parametric test and Spearman's correlation for samples paired by time (Zar, 1999). The relationship among flight activity (measured by the forager number) and the analysed abiotical factors (time, temperature and relative humidity) was verified by a quadratic polynomial nonlinear regression, where the geometric shape is a parable, fitting better to the interpretation of biological data (Zar, 1999;Silva et al, 2011). Finally, according to the type of transported material, the forage proportion was analysed to check possible diffences of these variables within and between seasons of the year (Kolmogorov-Smirnov test, p < 0.05).…”

Pollen and nectar foraging by Melipona quadrifasciata anthidioides Lepeletier (Hymenoptera: Apidae: Meliponini) in natural habitat

“…More than 1 / 3 of our data were recorded with RH above 90%, in the studied area. Silva et al, (2011) suggested that foragers from large species of Melipona use RH as indicator of pollen availability in the environment.…”