ONOSMA (BORAGINACEAE) POLLEN INTERACTIONS WITH BOMBUS TERRESTRIS (BUFF-TAILED BUMBLEBEE) SPECIES IN JORDAN

The relationships between pollen morphology of three Onosma species and their interactions with their insect visitors Bombus terrestris during springs seasons 2012 and 2013 were studied in Jordan. Pollen morphological characteristics (type and size of pollen grains, pollen shape, symmetrical structures between pollen grains and pollen visitors, polar and equatorial measurements, P/E ratios, structures of endo- and ecto- apertures) were investigated to formulate any possible way of interactions. Certain kind of bees Bombus terrestris (buff- tailed bumblebee) was observed as the most abundant visitor especially on the flowers of Onosma in April although many other honey bees like Apis mellifera, B. impatiens, A. dorsata and A. florea were observed but in very low frequencies. Onosma species in Jordan as all boraginacean species produces a large amount of whitish polliniferous dust, thus considered as a potential source for all pollen visitor species of bees, especially B. terrestris known as buff-tailed bumblebee. Three Onosma species were investigated palynologically by LM and SEM. The pollen class was either 3 zonocolporate (O. aleppica Boiss and Onosma frutescens Lam.) or 4-zonocolporate (O. cinerea Schreber). Polar measurements ranges were 37-43 μm for Onosma aleppica Boiss, 42-45 μm for O. cinerea Screber and 41- 44 μm for O. frutescens Lam. Equatorial measurement ranges were 26-34 μm for O. aleppica Boiss, 28-34 μm for O. cinerea Screber and 28-33 μm for O. frutescens Lam. P/E ratio ranged between 1.41 – 1.39 for O. aleppica, 1.49-1.33 for O. cinerea Schreber and 1.45-1.28 for O. frutescens Lam. The results of pollen outline indicated that equatorial view for all Onosma species was rectangular - elliptic; the polar view was triangular for all species. P/E ratio view was erect for all species examined. The most important diagonistic factor in recognition of pollen morphology of Onosma species was in the endoaperture and ectoaperture which showed some kind of variation reflected on their pollen visitor association. The morphology of ectoaperture structures (colpi , fastigium and margins) for the three species exhibited short colpi, absence of fastigium with indistinct margins for O. aleppica, long colpi, presence of fastigium and indistinct margin for O. cinerea Schreber and short colpi, presence of fastigium and distinct margin for O. frutescens Lam. The morphology of endoaperture structures (colpi, costae and margins) reflected also distinguished variation. O. aleppica showed short colpi, presence of costae and indistinct margin. O. cinerea showed short to long colpi in general, absence of costae and distinct margins.