In Melipona bees, gyne proportion is exceptionally high in relation to other genera of eusocial bees. However, hypotheses on caste determination in this genus predict gyne proportions above those usually observed. This may be because gyne production is limited by environmental conditions. Our aim was to investigate the influence of environmental factors on caste allocation in two species in the genus Melipona. Monthly caste production was monitored for almost 2 years. In Melipona interrupta, gyne proportion was negatively correlated to cumulative rainfall. However, in Melipona seminigra, caste allocation did not depend on environmental factors. Comparison among these and other congeneric species suggests that this variation reflects the diversity of food sources. Thus, although the mechanism of caste determination may be common to Melipona spp., caste allocation across species responds differently to environmental constraints. © 2013 INRA, DIB and Springer-Verlag France.
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