Materials and methods

Study area
Honey bee visitations on the plant species referred to were studied in the low altitude (<100 m) coastal lateritic terrain of Uttara Kannada district of (74^o 9’ to 75^o 10’E and latitude 13^o 55’ to 15^o 31’N) Karnataka State. The terrain studied is closer to the shores of the Arabian Sea, flanked towards its immediate east by the wooded hills and valleys of the Western Ghats. Most of the district, located towards the central Western Ghats west coast region, is characterized by high intensity seasonal rainfall (of 300-400 cm/year) from the South-west monsoon. Sizeable portion of rainfall receives during June to September. July to mid-September period, coinciding with high intensity rainfall, witnesses gregarious growth of ephemeral herbs with flowers of various hues, on these rocky expanses, a spectacle rarely referred to otherwise.

Most of the rocky terrain this time turns into a mosaic of seasonal wetlands, with its micro habitats like puddles, pools, streamlets, marshes and meadows teeming with plant life and insect community. Even the most denuded portions of indurated laterite get covered with gelatinous coating of blue-green algae. Shallow depressions, tubules and porosities in the rocks tend to have, clinging on them, insectivorous herbs like Droseras and Utricularias along with Eriocaulons. Seasonal pools and puddles are characterized by various hydrophytic herbs. Isolated amidst, in pockets of soil, occur leguminous herbs and stunted woody plants such as Sapium insigne, Memecylon umbellatum, F. indica, Ixora coccinea and some grasses. The tapering of rainfall from late September to almost its complete stoppage by end of November, marks the cessation of the herbal flora. The herbs and grasses dry up giving a brownish hue to the hills and plateaus.

Study organisms
Honeybees were mainly found visiting the flowers of the herbs Utricularia spp., Eriocaulon spp., Impatiens spp., and of a shrub F. indica and hence the study was restricted to these. Utricularias, or bladderworts, named so due to tiny bladders fitted with trap doors, are nectar producing insectivorous herbs. The laterite plateau bladderworts (Figure 1a), notably U. lazulina, U. reticulata and U. striatula are delicate, leafless plants with brilliantly coloured flowers. The Western Ghats and west coast have many species of balsams (Impatiens spp.), which produce attractive flowers with saccate or spurred corolla (Figure 1c). Impatiens raziana and I. rosea, are characteristic rainy season balsams of laterite plateaus. They are also notable producers of nectar for the bees35. The Eriocaulons grow on wet rocks, in marshes and meadows and freshwater pools and puddles. Of this pantropical herb, about 40 species occur in Karnataka and at least eight species occurred in the study areas. They are identified easily by their minute flowers aggregated into white, button-like inflorescences (Figure 1d). Their tiny petals are equipped with nectar producing glands. F. indica is a thorny shrub with small, unisexual, greenish-yellow flowers in short axillary or terminal sprays (Figure 1b).

Figure 1: a) A. dorsata on flower of Utricularias; b) A. dorsata on flower of Flacourtia indica; c) A. dorsata on flower of Impatiens rosea; d) Chilades laius on flower of Eriocaulon.

Sampling methods
The current study was carried out in 12 sampling stations from August to mid September 2012, during the peak flowering period for the herbs (Table 1). One of the sampling localities, a typical laterite plateau at Mugali (300 ha), in Honavar Taluk, was chosen for one time estimation of flower production, for the most prolifically occurring seasonal bee plants Utricularia spp. and Eriocaulon spp. A total of 65 quadrats (1 x 1 m each) were used along transect lines, leaving 20 m length intervals between quadrats, for counting number of flowers of the two above mentioned targeted genera, which contribute to the bulk of bee flower resources. After count of the total number of flowers (open ones and buds for Utricularia spp., and button-like flower heads bearing minute flowers in case of Eriocaulon spp.) from 65 quadrats, average number of flowers/m² was arrived at. These values are converted into standing floral wealth/ha of these two dominant ephemeral herbs of the laterite terrain.

Table 1: Sampling locality of different laterite plateau of Uttara Kannada district

For insect diversity and flower visitation rates, at each sampling station, three replicate plots of one m² were laid down and all the insects visiting the flowers in these plots were recorded. An insect visit was recorded only when the insect landed on the flowers. Flower visiting insects were identified using standard field keys from taxonomic literature^31-34. The insect visitation rates of four selected plants were measured in the quadrats. In each quadrat, three freshly opened flowers were observed for visitation counts of four species of honeybees (Apis dorsata, Apis cerana, Apis florae and Trigona sp.) for five minutes duration per flower. The more widespread Utricularia spp. and Eriocaulon spp. were examined altogether in 33 quadrats from 12 stations, whereas relatively lesser Impatiens spp., and F. indica were observed in nine quadrats each, in three sampling stations only. In addition, just to unravel the pollinator richness of laterite plateaus, the butterfly diversity also was recorded by walking along a 20 x 500 m belt transect, three transects per station. The observations were carried out during daytime only.

Similarities in butterfly taxonomic composition between sampling stations were measured by cluster analysis using Jaccard’s similarity index. Visitation rates of honeybees are illustrated using box plot. For each species sample group, the 25-75 percent quartiles represented using a box, the horizontal line within it indicating the median value. The minimum and maximum values are shown with short horizontal lines.