Insect pollinators and plant interactions: a taxonomic implications of pollen morphological features in melliferous plants

The current study was the fi rst report on pollen morphology of 17 species belonging to 11 different families that are particularly involved in nectar and pollen collection by honeybees from southern Pakistan using microscopic techniques. The plants were collected after being foraged by honeybees, identifi ed, and studied. Flowering periods, habits and localities of plants were examined. The pollen grains were then passed through the process of acetolysis, measured and both quantitative and qualitative characteristics evaluated. The investigated pollen grains varied in size, shape, colpi/pore and exine sculpturing. The most common type of pollen examined was tricolporate and among the shapes was oblate spheroidal one. Three types of exine sculpturing were observed, psilate, reticulate and echinate. The recorded pollen fertility ranged from 67 to 93 percent, showing that the considered plants are well established in the area. Brassica campestris L. Asphodelus tenuifolius Cav. and Astragalus hamosus L. resulted in the most visited species by honeybees. Our results showed that the pollen morphology of the melliferous plants in the study varies largely. The principal component analysis did not show clusters in relation to specifi c pollination syndromes and only some strictly phylogenetically related species were close in the graph. For this reason, the pollen grain characters can be considered suffi ciently diversifi ed to be used as markers for species identifi cation in melissopalynological analyses. The present study plays a vital role in taxa identifi cation, fl oral calendar preparation, and production of honey in the study area. This evidence may provide the possibility of evaluating the geographical provenance of honey from melissopalynological analysis at least in southern Pakistan.