Influência da temperatura no desempenho reprodutivo de abelhas Melipona interrupta Latreille, 1811 (Hymenoptera: Meliponini) em condições de laboratório

Abstract

Bees are important pollinators, especially the Meliponini tribe, known as indigenous sting-less bees, which has great importance for the pollination of native flora. Evidences of the influence of environmental factors on the production of queens and males throughout the year in different species of Melipona have been recorded. They need to maintain the internal temperature of the nests within a specific range to provide a proper development of the im-matures and protection to the adults from extreme outside temperatures, enabling the sur-vival of the colony. Climate change affect living beings, like bees, in different ways, each species has a different tolerance to environmental conditions. Thus, this study aimed to ver-ify the influence of temperature on reproductive development of the stingless bee Melipona interrupta, with emphasis on the proportions of males and females and mortality; differential expression of genes related to development and reproduction (hsp70, hsp90, dnmt3 e jhe); and body size of newly emerged bees exposed to different temperatures throughout the de-velopment. To fulfill these objectives, 21 colonies of Melipona interrupta, with equivalent development conditions, from Meliponary of GPA/INPA were separated into seven groups, with three hives each. The hives of the control group were kept at the Meliponary exposed to natural ambient temperature. The hives of the treatment groups were kept in the laboratory under different temperature ranges (artificially induced) in order to generate a thermal gra-dient. Sex and caste segregation was observed on disks sampled over time; differential gene expression was measured by real-time quantitative polymerase chain reaction; and size var-iation was compared by morphometry. External temperatures below 28 °C and above 30 °C increased immature mortality in M. interrupta colonies, and also provided clear evidence of effect on sex ratio in favor of females. Although phenotypic composition is expected to play an important role in colony function, our results clearly show that the effects of temperature on mortality are much stronger than on sex and caste segregation. The relative expression of the M. interrupta genes is clearly affected by the environment temperature, and varies by sex and caste. In general, the level of expression was higher in the workers, particularly in the lower temperatures. Using these genes as bioindicators of cell metabolism for climate change, we can understand that the species manages to maintain homeostasis, despite the higher physiological stress, at lower external temperatures. While high temperatures act as a limiting factor, and consequently higher mortality rate. We also observed the curve of the thermal effect on workers size in M. interrupta, in which, apparently, the metabolism is more efficient between 28 and 32 °C resulting in larger adults. As the average external tempera-tures diverges from this range, induce development of smaller adults. When comparing the species curve of thermal effect on size with the average temperature of the region, we con-clude that M. interrupta already lives near its thermal limit. The effects of climate change, coupled with species biology characteristics, demonstrate the vulnerability of Melipona in-terrupta, extendable to other species of the genus due to the biological and ethological prox-imity between them.