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Aims Nothapodytes nimmoniana (Family Icacinaceae) is a deciduous tree species distributed in Asia facing severe population decline. Wood chips from the tree are a source of camptothecin, a globally soughtafter alkaloid with cancer-treating properties, and are harvested unsustainably in natural forests. We studied the pollination ecology of the species and asked if there are constraints in pollination and fruiting success in its natural populations. We also discuss the potential effects of wood extraction on pollinators and reproductive success in the population. Methods The study was carried out during the flowering season in two populations with varying exploitation levels, both located in the Protected Area Network in the Western Ghats of Karnataka State. We assessed floral resource availability and measured pollinator diversity and activity in the canopy from the perspective of the biology of the species. We quantified pollinator abundance and percent fruit set as a function of population density. Important Findings Flowers belong to the fly pollination syndrome and are open to visits by generalists such as Apis dorsata and Trigona iridipennis. Fruiting success did not vary between exploited and unexploited sites, but there was a significant difference in pollinator assemblage. In a lean male flowering year, fruit set was low, suggesting pollen limitation in the population. No fruiting was recorded in the second year at the site where trees were felled soon after the flowering period. We argue that when male floral resources are altered in exploited populations, pollinators of generalist nature may show a shift in foraging pattern. Also, generalist plants may be as susceptible to pollination loss as are specialist plants. The need for outcrossing in the species would probably exacerbate this vulnerability.

Camptothecin (CPT), a monoterpene alkaloid, is an important anti-cancer compound obtained from several plant sources including Camptotheca acuminta (from China) and Nothapodytes nimmoniana (from India). Currently, by far the highest levels of CPT (approximately 0.3% w/w) are reported from Nothapodytes nimmoniana, a small tree distributed in the Western Ghats, India. In recent years because of the heavy demand, there has been a serious threat of extinction of the populations of the tree in the Western Ghats forest of south India. Several studies have chemically profiled populations of the species in the Western Ghats to identify sources of high yield and therefore to enable the sustainable production and harvesting of CPT. In this study, using both high-performance liquid chromatography and liquid chromatography-mass spectrometry, we report for the first time the identification of trees that produce at least 5- to 8-fold more CPT than hitherto reported. Furthermore, we show for the first time the production of a few minor camptothecines, including 10-hydroxy camptothecin, in the stem and root bark extracts of the tree. These results have important implications for not only harnessing the high-yielding individuals for clonal multiplication but also for exploiting some of the minor camptothecines, which also have been shown to have important anti-cancer and anti-viral activity.

Differential development of sinks that depend on a common resource pool has been viewed as a consequence of an autocatalytic feedback process of flow of resource units into them. The feed-back process implies that the stronger a sink is relative to its competitors, the greater is its probability of getting further resources as a non-linear function of its resource drawing ability and sink size. We show that this model contrasts with that of the sink-strength dependent model in its prediction of the subsequent development of the initial asymmetry of growing leaves when their resource drawing ability is enhanced. By artificially enhancing the resource drawing ability of the leaves of Mestha (Hibiscus cannabinus L.) by external application of growth regulators, we test these predictions and show that the results are in conformity with the autocatalytic model proposed by Ganeshaiah and Uma Shaanker.