Neelkamal Rastogi

Role of floral repellents in the regulation of flower visits of extrafloral nectary-visiting ants in an Indian crop plant

Abstract 1. Field investigation of the association between sponge gourd, Luffa cylindrica plants and its ant visitors revealed that five of the six most frequent species: Camponotus compressus, C. paria, Pheidole sp., Pachycondyla tesserinoda and Tetramorium sp. mainly visited the extrafloral (EF) nectaries present on the leaves, bracts, bracteoles and calyx of the plant. Tapinoma melanocephalum was the only ant species observed at the floral as well as the EF nectaries.

Deterrent effect of a guild of extrafloral nectary‐visiting ant species on Raphidopalpa foveicollis, a major insect pest of sponge gourd, Luffa cylindrica

Among the 10 ant species visiting the extrafloral nectaries of sponge gourd plants [Luffa cylindrica L. (Cucurbitaceae)], Camponotus compressus (Fabricius) (Hymenoptera: Formicidae) appears to be the ecologically dominant species, due to its abundance and the high frequency of deterrent encounters with the major insect herbivore, Raphidopalpa foveicollis Lucas (Coleoptera: Chrysomelidae). A significant positive linear correlation was found between the number of extrafloral nectaries per leaf, calyx, bract, and bracteole and the patrolling time of C. compressus, Camponotus paria (Emery), Pheidole spec., and Tetramorium spec. (all Hymenoptera: Formicidae) at the corresponding plant parts. Many one‐to‐one deterrent interactions between the ant visitors and adult R. foveicollis were recorded, with C. compressus being involved in most encounters on the calyx and bracts, Pheidole spec. on the leaves, and Pachycondyla tesserinoda (Emery) (Hymenoptera: Formicidae) on the bracteoles. Tapinoma melanocephalum (Fabr.) (Hymenoptera: Formicidae) exhibited significant deterrent effects on adult herbivores on the corolla when in groups larger than 15 ants. Ant exclusion and inclusion experiments revealed a significant reduction in the residence time, as well as dose‐ and time‐dependent reduction in the frequency of visits of the herbivore on crop plants with C. compressus, C. paria, Pheidole spec., and T. melanocephalum ants, compared to the control. Results support the optimal defence hypothesis, as the plant structures most closely linked to plant fitness bear the extrafloral nectaries and are defended by the visiting ant species. This is a valuable, indirect plant‐protection strategy of an annual crop plant.

Prey concealment and spatiotemporal patrolling behaviour of the Indian tree ant Oecophylla smaragdina (Fabricius)

Summary:Oecophylla smaragdina workers conceal prey with leaves and twigs on discovering large prey on their ground territory. The prey concealment behaviour occurs concurrently with prey capture and killing. Ants were observed conducting spatiotemporal patrolling around large prey. The garden lizard Calotes versicolor and at least two predatory ant species were found to forage in the same area as O. smaragdina. It is suggested that the prey concealment behaviour of Oecophylla may be a strategy to prevent prey detection by vertebrate predators which use vision to prey on similar large prey species.

Heavy metal accumulation and ecosystem engineering by two common mine site-nesting ant species: implications for pollution-level assessment and bioremediation of coal mine soil

The present study focuses on the abundance, heavy metal content, and the impact of ecosystem engineering activities of two coal mine site-inhabiting ant species, Cataglyphis longipedem and Camponotus compressus. The abundance of Ct. longipedem increased while that of C. compressus decreased, with increasing soil pollution. Correspondence analysis reveals a close association between soil heavy metal concentrations and Ct. longipedem abundance, but this association is lacking in the case of C. compressus. Cataglyphis ants which occupy stress-characterized niches appear to be pre-adapted to tolerate heavy metal pollution. Higher concentrations of Zn and Mn in Ct. longipedem may contribute to the strengthening of the cuticular structures, necessary for nest excavation in the hard, arid soil and for single load carrying. C. compressus ants appear to be pollution sensitive. Their higher Fe content may be related to metal uptake via plant-derived liquids and species-specific regulatory mechanisms. The metal pollution index and biota-to-soil accumulation factors, calculated by using the ant body metal content of the two species, indicate an overall decrease of soil heavy metal concentrations with increase of the site age, which reflects the degree of pollution related to the mine site age. The concentrations of total and available heavy metals (Fe, Zn, Mn, Pb, and Cu) were significantly lower in the ant nest debris soil as compared to the reference soil. The results of the present study highlight the role of ants as bioindicators and in bioremediation of contaminated soil.

Contribution of the nutrient-enriched ant nest debris soil to growth and yield of Kalmegh (Andrographis paniculata) under natural and experimental field conditions

Abstract Andrographis paniculata, commonly known as Kalmegh, is an important medicinal plant which exhibits a range of pharmacological characteristics. The present study revealed that under natural and experimental field conditions, the debris soil of the ground-nesting ant (Pheidole latinoda) colonies increased soil fertility and yield of this plant. The growth of Kalmegh planted in the debris amended soil was significantly enhanced in a dose-dependent manner. The yield, in terms of number of branches, number of leaves, plant biomass and number of pods plant−1 was consistently higher for plants grown in debris amended treatments as compared with plants grown in control soil. Concentrations of total C, P, available N (NH4-N, NO3-N) and microbial biomass C and P were significantly higher in the various debris amended soil treatments as compared with the control soil. Significant positive correlations were found between the ecophysiological traits of Kalmegh plants, i.e. leaf area, total biomass and number of fruits plant−1, and the soil chemical properties of the soil. Under natural field conditions also the biomass of Kalmegh plants growing within 5 m distance of P. latinoda nests was significantly higher as compared with plants located at a distance >10 m. Overall, the results suggested that the ecosystem engineering activities of P. latinoda colonies have the potential to contribute to soil fertility and thereby promote enhanced growth and yield of this medicinally important plant. Since colonies of ground-nesting ant species, such as P. latinoda, are abundant in annual cropping systems, they can contribute to agricultural sustainability.

Pollution vis-a-vis Biodiversity

Widespread pollution has been regarded as the most probable contributing cause responsible for recent biodiversity related regional or global problems such as the appearance of phytoplankton blooms, decline of amphibians, bleaching of coral reefs, mass mortality among seals and dolphins. Significantly, it has been found that pollution seems to be most harmful when it works alongwith other stresses such as aquatic eutrophication, other forms of habitat disruptions and factors which induce immunosuppressions. In view of this, it becomes important to understand the effect of pollution on biodiversity on the basis of available research information, so that we can alert ourselves before biodiversity loss (Myers, 1995; Agrawal & Agrawal., 2000).